Research Article Spectra and Charge Transport of Polar ...

Research ArticleSpectra and Charge Transport of PolarMolecular Photoactive Layers Used for Solar Cells

Yuanzuo Li1 Dawei Qi1 Chaofan Sun1 and Meiyu Zhao2

1College of Science Northeast Forestry University Harbin Heilongjiang 150040 China2Institute of Theoretical Simulation Chemistry Academy of Fundamental and Interdisciplinary SciencesHarbin Institute of Technology Harbin Heilongjiang 150080 China

Correspondence should be addressed to Yuanzuo Li yuanzuoligmailcom and Dawei Qi qidw98066126com

Received 1 April 2015 Revised 14 June 2015 Accepted 23 June 2015

Academic Editor Luz Maria Rodriguez-Valdez

Copyright copy 2015 Yuanzuo Li et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The ground state structures HOMO and LUMO energy levels band gaps ΔH-L ionization potentials (IP) and electron affinities(EA) of three types of copolymer P1 and its derivatives P2 P3 and PBDT-BTAwere investigated by using density functional theory(DFT) with B3LYP and 6-31G (d) basis set On the base of optimized structures of ground states their absorption spectra wereobtained by using TD-DFTCam-B3LYP6-31 G (d) Research shows that with the increasing conjugated units HOMO energylevels increased LUMOenergy levels decreased and band gaps decreased graduallyMoreover their ionization potentials decreasedand electron affinities increased along with the increase of conjugated chains and absorption spectra red-shifted In addition theside chain has a significant effect on the properties of ground and excited states In order to investigate the influence of conjugatedunits and side chain on the charge transport their hole and electron reorganization energies were calculated and the resultsindicated that Pb have a good hole transport capability Considering the practical application the HOMO and LUMO energylevels band gaps and absorption spectra under external electric field were studied and the results proved that the external electricfield has an effect on the optical and electronic properties

1 Introduction

Electrically conducting polymers have been considered fornumerous applications [1ndash4] such as organic thin-film tran-sistors conducting textiles and solar cell Donor-acceptorconjugated molecules are viewed as a kind of very attrac-tive organic semiconductors because of their high chemicalstability and uncommon versatility [5] The semiconduc-tors suitable as single component channel materials shouldfacilitate the formation of an exciton through the cationand anion radicals and they show both stable hole andelectron transporting characteristics on the other hand thesemiconductors are required to have a good match betweentheir structures and metal electrodes to balance the chargeinjection barriers between the relative positions of HOMOand LUMOenergy levels and the work function of electrodes

For polymer solar cells (PSCs) donor-acceptor conju-gatedmolecules as a p-type semiconductor should have goodoptical response and match of energy levels For polymer

solar cells the photocurrent is generated after five process[6] (1) the active layer absorbs photons to produce excitons(2) excitons transfer to the donor-acceptor (D-A) interface(3) excitons separate at the donor-acceptor interface andform free charges (4) charges transport under an electricfield (5) charges are collected by electrodes At presentmuch works have been done [7ndash18] and the photocurrentconversion efficiency (PCE) of polymer solar cells is still verylow (reaching to about 10) [7ndash10 12 16 17] how to improveits PCE is a key question for the purpose of realizing thecommercialization and competing with traditional inorganicsilicon photovoltaic cells The main factors limiting thePCE of polymer solar cells have three points [11ndash13] (1) theresponse range of active layer does not match with the solarspectrum (2) the dissociation of excitons is difficult (3) thecarrier mobility of materials in current active layer seemsvery low compared with that of traditional inorganic siliconcrystals In order to improve the photocurrent conversionefficiency of polymer solar cells from the above aspects

Hindawi Publishing CorporationJournal of ChemistryVolume 2015 Article ID 964252 10 pageshttpdxdoiorg1011552015964252

2 Journal of Chemistry

researchers havemade great efforts Mori et al [14] fabricatedlow-band gap donoracceptor polymer blend solar cellspresenting a short-circuit current density of 885mA cmminus2a fill factor of 055 an open circuit voltage of 084V andthe high PCE of 4 which demonstrates the potentialof polymerpolymer blend solar cells as an alternative topolymerfullerene solar cells Klider and coworkers [15]synthesized the copolymer poly(2-methoxy-5-bromo-p-phe-nylenevinylen)(25-dicyano-p-phenylenevinylene)(MB-PPVDCN-PPV) using an electrochemical method and the con-clusions by cyclic voltammetry (CV) UV-Vis and fluo-rescence (FL) spectroscopy showed that the conduction bandis more stabilized in the copolymer than in homo polymerKim et al [16] designed and synthesized a new poly48-bis((2-ethylhexyl)thieno [32-b]thiophene)-benzo[12-b45-b1015840]dithiophene-alt-2-ethylhexyl-46-dibromo-3-fluorothieno[34-b]thiophene-2-carboxylate (PTTBDT-FTT) and anorganic thin-film transistor showed high hole mobility of 21times 10minus2 cm2(Vsdots) and they also fabricated a single-junctionbulk heterojunction photovoltaic cells inverted photovol-taic cells and a tandem photovoltaic device comprisingPTTBDT-FTT showing a maximum power conversionefficiency (PCE) of 744 771 and 866 respectively Inaddition researchers also have committed to design novelactive layer materials with low-band gaps and high carriermobility Yu and coworkers [17] designed four new D-Acopolymers PCDT-BDPD (P1b) PDTC-BDPPD (P2b)PBDTTF-BDPD (P3b) and PBDTF-BDPD (P4b) based ondiketopyrrolopyrrole (DPP) polymers and the predictedPCEs of the new donor polymers reached up to about 10in theory Narayanana et al [18] designed and synthesized aseries of 34-ethylenedioxy thiophene (EDOT) and quinox-aline donor-acceptor (D-A) copolymers P(EDOT-ACEQX)P(EDOT-BZQX) and P(EDOT-PHQX) exhibiting electro-chemical band gap of 105 10 and 099 eV respectively

In this work density function theory (DFT) was usedto study three types of copolymers [19] a copolymer con-taining BDT and thiophene units in the main chain (noconjugated side-chain) and the copolymer is abbreviated asP1 introducing a conjugated side chain with no electron-withdrawing group into P1 which was named after P2introducing a side chain with an electron-withdrawing groupinto P1 which was named after P3 Optical electrochemicaland photovoltaic properties of P1 P2 and P3 were studied(see Figure 1) they are compared with those of a main chaintype copolymer PBDT-BTA to get an insight into the effectof the introduction of conjugated side chain on photovoltaicproperties of the conjugated copolymers

2 Computational Methods

The molecular geometries of the several oligomers P1 P2P3 and Pb (119899 = 1ndash3) were fully optimized using the DFT[20 21] with B3LYP functional [22ndash24] All calculationsin this work were carried out using Gaussian 09 programpackage [25] The 6-31G (d) basis set was used for allcalculations The HOMO LUMO and gap (HOMO-LUMO)energies were also deduced for the stable structures and

electron density corresponding to energy levels was studiedIt is worth noting that DFT gives Kohn-Sham orbitals notmolecular orbitals which uses the KS orbitals to approximatethe properties of the HOMO and LUMO DFT combinedwith electron density analysis has been successful to inves-tigate several series of polymers and charge transfer processunder photon excitation [26ndash29] Reorganization energieswere obtained by means of calculation of the single pointenergy at the DFTB3LYP level6-31G(d) followed by theoptimized geometries of different states (the neutral cationicand anionic geometries) Electronic transition energies andoscillator strengths of oligomers were obtained by using timedependent density functional theory (TDDFT) [30] at theCam-B3LYP6-31G (d) level [31] which contains 65 long-range HF exchange

3 Results and Discussion

31 Structural Properties The ground state structures of P1P2 P3 and Pb were optimized using DFTB3LYP with 6-31G (d) basis set The computing values (compromising thebond lengths and dihedral angles for their tripolymers) werelisted in Table 1 and the number of atoms for the tripolymersstructure of P1 and Pb were labeled in Supporting Materials(see Figure S1 in Supplementary Material available online athttpdxdoiorg1011552015964252) and optimized carte-sian coordinates and total energies were listed in Tables S1ndashS4 Compared to the bond length at same position of P1 P2and P3 one can find the bond lengths for P3 that present thebiggest values in the three molecules and the value for P1 isthe smallest For C2-C3 the values for P1 P2 and P3 were1444 1446 and 1447 respectively It indicates that there isalmost no change upon introducing a C=C and thiopheneinto the side chain of P1 and a cyan into the side chain of P2

Moreover it can be seen in Table 1 that the averagedihedral angle of P3 is the biggest among P1 P2 and P3indicating the conjugated main chain of P3 twisted seriouslyFor example C1-C2-C3-S4 S4-C5-C6-C7 C8-C9-C10-S11S11-C12- C13-C14 and C15-C16-C17-S18 for P3 are minus151∘367∘ minus76∘ 357∘ and minus143∘ respectively and for P1 they areminus39∘ 39∘ minus75∘ 77∘ and minus91∘ respectively So the structureof ground state for P1 tends to flatten among the threemolecules But comparing P1 with Pb the average dihedralangle of Pb seemed smaller than that of P1 One can makea conclusion that introducing a side chain can change thecoplanarity at the micro level

32 HOMO LUMO and Band Gaps (Δ119867-119871) The HOMO

and LUMO energy levels and band gaps ΔH-L (differencebetween HOMO and LUMO) of the oligomers (119899 = 1 2 3)are computed and the results are given in Table 2 Moreoverthe energy levels and band gaps of the polymers are obtainedby the extrapolation As shown in Table 2 with the increasingconjugated units HOMO energy levels increased slightly andLUMO energy levels decreased obviously and the band gapsΔH-L present a decreased tendency Moreover it can be seenin Figure 2 that with the increasing of conjugatedmain chainthe HOMO energy levels of the four molecules have a tinychange but the LUMO energy levels of that change obviously

Journal of Chemistry 3

Table 1 Selected optimized bond length and dihedral angles of P1 P2 P3 and PBDT-BTA (Pb) for unit 119899 = 3

P1 P2 P3 PbBond length (A)

C2-C3 1444 1446 1447 C2-C3 (1444) C16-C17 (1443) C30-C31 (1444)C5-C6 1443 1450 1451 C6-C7 (1459) C20-C21 (1459) C34-C35 (1462)C9-C10 1443 1446 1446 C7-C8 (1374) C21-C22 (1375) C35-C36 (1372)C12-C13 1444 1449 1450 C8-C9 (1432) C22-C23 (1432) C36-C37 (1435)C16-C17 1448 1447 1448 C12-C13 (1442) C26-C27 (1442)

Dihedral angles (∘)C1-C2-C3-S4 minus39 minus107 minus151 C1-C2-C3-S4 (minus118) C19-C20-C21-C22 (minus94) C35-C36-C37-C38 (19)S4-C5-C6-C7 39 327 367 C5-C6-C7-C8 (121) C21-C22-C23-C24 (minus05)C8-C9-C10-S11 minus75 minus139 minus76 C7-C8-C9-C10 (16) C25-C26-C27-S28 (37)S11-C12-C13-C14 77 328 357 C11-C12-C13-S14 (13) C29-C30-C31-S32 (minus80)C15-C16-C17-S18 minus91 102 minus143 C15-C16-C17-S18 (minus08) C33-C34-C35-C36 (151)

P1 P2

P3 PBDT-BTA (Pb)

Figure 1 Chemical structures of P1 P2 P3 and PBDT-BTA (Pb)

while the band gaps have a good linear relationship with thereciprocal of conjugated unit 119899 (see Figure S2)

Comparing P1 with P2 the HOMO and LUMO and bandgaps for each of their conjugated unit (119899 = 1 2 3) haverough equal values (corresponding error of about 007 eV)But contrasting the energy levels of P3 with P1 one canfind that their LUMO energy levels have bigger differencesthan that of P1 and P2 In order to have a comprehensiveinvestigation one compared the energy levels of P3 with Pband found that the LUMO energy levels of Pb are lower thanthat of P3 However their HOMO energy levels also have asmall difference In a conclusion the HOMO energy level ofthe four molecules is in this order Pb gt P3 gt P2 gt P1 theirLUMO energy level is in this order Pb lt P3 lt P2 lt P1 So theirband gaps are in this order Pb lt P3 lt P2 lt P1 and change ofenergy gap results in bathochromic shifts in their absorptionfrom Pb to P1

Considering the fullerene-based heterojunction photo-voltaic cells copolymer as electron donor should have goodenergymatch with fullerene (such as [60] PCBM) Usually intheory open voltage can be estimated through the followingequation

119881oc = (1119890) [1003816100381610038161003816119864HOMO (119863)

1003816100381610038161003816 minus1003816100381610038161003816119864LUMO (119860)

1003816100381610038161003816] minus 03119881 (1)

where 119890means element electronic 119864HOMO(119863) and 119864LUMO(119860)mean the donor HOMO energy and acceptor LUMO energyrespectively 03 is the experience constants [32] For P1ndashPbas electron donor 119864HOMO(119863) energies are minus479 eV minus474 eVminus499 eV and minus493 respectively 119864LUMO(119860) for [60] PCBMwas obtained to be minus309 eV at the DFTB3LYP6-31G(d)From (1) the difference between 119864HOMO(119863) and 119864LUMO(119860)with relatively large value has relatively higher open circuitvoltage It can be seen that the 119864HOMO of P3 and Pb are


Table 2 Energy levels of HOMO and LUMO and energy gaps ΔH-Lof P1 P2 P3 and PBDT-BTA (Pb)

Molecules Units LUMO (eV) HOMO (eV) ΔH-L (eV)

P1

119899 = 1 minus147 minus504 357119899 = 2 minus207 minus489 282119899 = 3 minus228 minus489 261119899 = infin minus268 minus479 211

P2


P3


Pb


Pb

P2

P3

P1

Ener

gy le

vel (

eV)

HOMOLUMO

minus55

minus50

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10

Figure 2 HOMO and LUMO energy levels of the oligomers (119899 =1 2 3)

lower than that of P1 and P2 molecules suggesting that theincreased conjugated length can obtain relatively higher opencircuit voltage

Figure 3 shows HOMOs and LUMOs surface plots of thefour tripolymer FromFigure 3 it can be seen that the electrondensities of the HOMO of P1 are distributed on the wholemain chain and the electron densities of HOMO of P2 P3andPb are distributed on the left of themoleculeThe electrondensities of LUMO of the four molecules are distributed onthe middle part of the main chain

33 Ionization Potentials and Electron Affinities Ionizationpotentials and electron affinities can predict the transportbarrier of hole and electron in the organic solar cells [3334] In order to explore the hole and electron transport

Table 3 Ionization potentials and electron affinities of P1 P2 P3and PBDT-BTA (Pb) (eV)

Units P1 P2 P3 PbIP EA IP EA IP EA IP EA

119899 = 1 617 030 601 050 615 092 604 135119899 = 2 569 121 558 135 577 166 567 203119899 = 3 562 157 547 161 572 193 554 229119899 rarr infin 530 218 518 218 547 242 529 274

the ionization potentials (IP) and electron affinities (EA) ofthe four oligomers were calculated and the results are listedin Table 3 As shown with the increasing conjugated unit IPdecreased and EA increased It indicates that the injectionability of hole and electron is improved with the increaseof conjugated unit Figure 4 shows the relationship betweenionization potentials and electron affinities and the reciprocalof conjugated unit (1119899) It can be seen in Figure 4 that the IPand EA have a good linear relationship with the reciprocalof conjugated unit Consequently the IP and EA of the fourpolymers are obtained by the extrapolation Table 3 showsthat the IPs are 530 eV 518 eV 547 eV and 529 eV for P1P2 P3 and Pb respectively indicating that the injectioncapability of hole is in this order P2 gt Pb gt P1 gt P3 Inaddition the values of EA are 218 eV 218 eV 242 eV and274 eV for P1 P2 P3 and Pb respectively and the injectioncapability of electron is in this order Pb gt P3 gt P1 = P2

34 Absorption Spectra On the basis of optimized groundstate structures the absorption spectra of the four oligomers(119899 = 1 2 3) were investigated by TD-DFTCam-B3LYP6-31G (d) method and the results are listed in Table 4 andTables S5ndashS8 It can be seen from Tables S5ndashS8 that withthe increasing conjugated units the maximum absorptionpeaks of the four molecules have a red shift and the oscillatorstrengths increased except for P3 When 119899 = 2 the oscillatorstrengths of P3 reached to themaximum1554 (1169 and 1264for 119899 = 1 and 3 resp) From Table 4 it is found that thefirst excited state (S1) of the four tripolymers consists of theelectron transition from HOMO to LUMO and the corre-sponding absorption peaks are 2815 eV (4405 nm) 2877 eV(4309 nm) 221 eV (5610 nm) and 2409 eV (5147 nm) forP1 P2 P3 and Pb respectively The site of absorption of fourmolecules shows that molecules P3 and Pb with increasingconjugated length display red-shifted absorption comparedwith the molecules P1 and P2

Figure 5 shows the absorption spectra of P1 P2 P3and Pb for 119899 = 1 and 119899 = 3 From Figure 5 one cansee that with the increasing conjugated units the maximumabsorption peak of P3 have an obvious red shift about568 eV (2182 nm) and also the oscillator strength increasesmultiplied Comparing with 119899 = 1 the maximum absorptionpeak of other molecules (119899 = 3) red-shifted about 115 eV(1078 nm) 1322 eV (938 nm) and 1196 eV (1037 nm) forP1 P2 and Pb respectively Among them the absorptionpeak of P3 is the maximum and that of P2 is the minimumComparing the absorption spectra of P3 with the other threemolecules it can be found that P3 have a red shift and


Table 4 Transition energy and oscillator strengths for four molecules (119899 = 3)

Molecules State Transition energy (eVnm) Strength 119891 Contribution MO

P1

1 28154405 119891 = 3552 Hrarr L0614492 32553809 119891 = 0020 H-1rarr L0458313 35953449 119891 = 0464 H-2rarr L0496084 37453311 119891 = 0038 H-4rarr L0440235 38163249 119891 = 0040 H-3rarr L036946

P2

1 28774309 119891 = 2856 Hrarr L0589982 31883889 119891 = 0675 Hrarr L+10467503 36013444 119891 = 1096 H-2rarr L0309694 37013351 119891 = 0559 H-4rarr L0345705 37283326 119891 = 0148 H-5rarr L046236

P3

1 22105610 119891 = 1264 Hrarr L0661102 23845200 119891 = 0218 Hrarr L+10618563 24425078 119891 = 0275 H-1rarr L0589724 25654834 119891 = 0249 H-1rarr L+10520395 26384699 119891 = 0008 Hrarr L+2063202

Pb

1 24095147 119891 = 6003 Hrarr L0524752 26864616 119891 = 0099 Hrarr L+10471913 30304092 119891 = 0583 H-1rarr L+20296114 32833777 119891 = 0030 H-2rarr L0333635 34063640 119891 = 0127 H-2rarr L+1035426

LUMOHOMO

P1

P2

P3

Pb

Figure 3 HOMOs and LUMOs surface plots of P1 P2 P3 and PBDT-BTA (Pb) (119899 = 3)

the values are 1029 eV (1205 nm) 953 eV (1301 nm) and2678 eV (463) nm for P1 P2 andPb respectivelyThe secondabsorption peaks corresponding to the excited state (S2) havea similarity for the fourmolecules It can be seen fromTable 4that all the second absorption peaks of P1 P2 P3 and Pbcorrespond to the excited state S3 Transition energy of S3 is3449 nm 3444 nm 5078 nm and 4092 nm and absorptionstrengths are 0464 1096 0275 and 0583 with compositionof H-2rarr L H-2rarr L H-1rarr L and H-1rarr L+2 respectively

35 Reorganization Energies The reorganization energy canbe used to estimate the charge transfer characteristic inorganicmaterial According to theMarcus theory [35 36] thecharge transfer rate can be expressed by the following formula[35]

120581119864119879

= 119860 exp [ minus1205824120581119861

119879] (2)


IPEA

IPEA

03 11100908070605040

1

2

3

4

5

6

P1

Ener

gy (e

V)

1n 1n

1n 1n

03 11100908070605040

1

2

3

4

5

6

P2

Ener

gy (e

V)

03 1110090807060504

1

2

3

4

5

6

P3

Ener

gy (e

V)

03 11100908070605041

2

3

4

5

6

Pb

Ener

gy (e

V)

y = minus186x + 218

R2 = 0997

y = 086x + 530

R2 = 0969

y = minus167x + 218

R2 = 0999

y = 082x + 518

R2 = 0995

y = minus151x + 242

R2 = 0999

y = 067x + 547

R2 = 0963

y = minus140x + 274

R2 = 0998

y = 075x + 529

R2 = 0999

Figure 4The relationship between ionization potentials (IP) and electron affinities (EA) of P1 P2 P3 and PBDT-BTA (Pb) and the reciprocalof conjugated unit (1119899)

where 119879 is the temperature 120581119861

is the Boltzmann constant120582 is reorganization energy and 119860 is electronic couplingAmong them the reorganization energy is divided intotwo forms [37ndash40] one is the intermolecular reorganizationenergy and another is the intramolecular reorganizationenergy However the intermolecular reorganization energyhas a tiny relationship with the charge transfer rate and hasno significant effect on the electron transfer [39ndash41] Theintramolecular reorganization energies 120582

ℎ

(which is definedas the reorganization energy of hole) and 120582

119890

(which is definedas the reorganization energy of electron) can be expressed bythe following formula

120582119890

= (119864minus

0 minus119864minus) + (1198640minus

minus1198640)

120582ℎ

= (119864+

0 minus119864+) + (1198640+

minus1198640)

(3)

where 119864+0

(119864minus0

) is energy of the cation (anion) calculatedwith the optimized structure of the neutral molecule 119864

+

(119864minus

) is the energy of the cation (anion) calculated with theoptimized cation (anion) structure 1198640

+

(1198640minus

) is the energy ofthe neutral molecule calculated at the cationic (anionic) state1198640

is the energy of the neutral molecule at the ground stateThe calculated molecular reorganization energies of P1 P2P3 and Pb were listed in Table 5 The results present variouschanges with the increase of conjugated units

When the conjugated unit 119899 = 1 hole reorganizationenergies are in this order P2 lt Pb lt P3 lt P1 in which P2and Pb have a lower hole reorganization energies electronreorganization energy is in this order P2 lt P3 lt Pb lt P1But when 119899 = 2 the electron reorganization energy of thefour molecules is in this order Pb lt P1 lt P2 asymp P3 which havethe same tendency with that of the tripolymers In additionthe hole reorganization energy of the dipolymers is in this


200 6005004003000

16

32

48

64

Abso

rptio

n

Wavelength (nm)

P1P2

P3Pb

times103

(a)

200 9008007006005004003000

60

120

180

240

Abso

rptio

n

Wavelength (nm)

times103

P1P2

P3Pb

(b)

Figure 5 Absorption spectra of P1 P2 P3 and PBDT-BTA (Pb) for (a) 119899 = 1 and (b) 119899 = 3

Table 5 Calculated molecular reorganization energies of fourmolecules (times10minus1 eV)

P1 P2 P3 Pb

119899 = 1120582119890

310 245 268 287120582ℎ

467 312 382 377

119899 = 2120582119890

250 324 324 186120582ℎ

358 230 386 269

119899 = 3120582119890

192 254 255 129120582ℎ

281 198 218 185

order P2 lt Pb lt P1 lt P3 which is different from that of thetripolymers Pb lt P2 lt P3 lt P1 In conclusion Pb have a goodhole transfer capability

36 Field Effect on Optical Character For solar cells electricfield originates from the p-n heterojunction [42] In practicalapplication the active layer in the solar cell panel will beaffected by the electric field produced by the system resultingin the properties of changing spectra The absorption peaksand oscillator strengths of P1 P2 P3 and Pb (119899 = 1 2) underexternal electric field are listed in Table S9 and Table 6

Along with the increasing electric field strengths (119865 =1times10minus3 2times10minus3 and 3times10minus3 au) the transferred orientation

of the charge is along the molecular skeleton Table S9 showsthat the change of the absorption peaks of monomers is notobvious indicating that the external electron field has nosignificant effect on the optical properties of the monomersWhen 119899 = 2 the absorption spectra of all the moleculesspectra have an evident red-shift with the increase of externalelectronfield and the red-shifted values are 386 nm 348 nm1159 nm and 6472 nm for P1 P2 P3 and Pb respectivelyComparing the absorption spectra under 119865 = 3 times 10minus3 auPb has a remarkable red-shift (6601 nm) and P3 presentsa small red-shift (198 nm) indicating that when 119899 = 2

the influence of external electron field on the optical propertyof Pb is interesting But in the sake of the oscillator strengththe external electron field makes the absorption strength ofPb decrease maximally (from 3536 to 0066) which is badfor the performance of the organic solar cells

Table 7 and Table S10 give the HOMO snd LUMO energylevels and band gaps of P1 P2 P3 and Pb (119899 = 1 2) underexternal electric field It can be seen in Table S10 that theexternal electron field still has no obvious effect on the energylevels and band gaps of the monomers so we do not giveover much attention to the monomers Figure 6 gives thechange of energy levels of the dipolymers with the increasingelectron field and the specific results (see Table 7) FromFigure 6 one can find that with the increase of electron fieldHOMO increased and LUMO decreased obviously in whichthe HOMO energy level is in this order Pb gt P2 asymp P3 gt P1LUMOenergy level is in this order PbltP3ltP2ltP1 Figure 7shows the change tendency of band gaps with the increase ofexternal electron field As shown it can be seen that the bandgaps are decreased in different degrees with the increasingelectron field inwhich the band gaps of P3 changed obviously(156 eV) but the band gaps of Pb are the least correspondingto each of electron field strengths (157 eV 058 eV and 021 eVfor 119865 = 1 times 10minus3 2 times 10minus3 and 3 times 10minus3 au resp) indicatingthat Pb have good photoelectric properties

4 Conclusion

The properties of ground state and excited state of poly[(ben-zodithiophene- 26-diyl)(25-thienylene)] (P1) and its deriva-tives P2 P3 and PBDT-BTA (Pb) were investigated byusing DFTB3LYP6-31G(d) and TD-DFTCam-B3LYP6-31G(d) method respectively The results of energy levelsand absorption spectra showed that with the increasingconjugated length the site of absorption peak of moleculesP3 and Pb displays the red-shifted absorption compared


Table 6 Absorption spectra and oscillator strengths of the dipolymers under external electric field

Field (times10minus3 au) P1 P2 P3 Pb1 4151 (2157) 4143 (1864) 4235 (1481) 5011 (3536)2 4278 (1991) 4255 (1730) 4383 (1278) 5769 (0974)3 4537 (1662) 4491 (1444) 5394 (0001) 11483 (0066)

Table 7 HOMO and LUMO energy levels and band gaps of the dipolymers under external electric field (eV)

Field (times10minus3 au) P1 P2 P3 PbH L ΔH-L H L ΔH-L H L ΔH-L H L ΔH-L

1 minus483 minus213 270 minus476 minus207 269 minus482 minus266 216 minus465 minus309 156



32

1

Pb

P3

P2P1

Ener

gy le

vel (

eV)

HOMOLUMO

minus18

minus20

minus22

minus24

minus26

minus28

minus32

minus34

minus36

minus38

minus30

minus42

minus44

minus46

minus48

minus40

minus50

Figure 6 The changes of energy level of the dipolymers with theincreasing electric field

10 30252015

020406081012141618202224262830

Ener

gy g

ap (e

V)

P1P2

P3Pb

F (10minus3 au)

Figure 7The changes of band gap of the dipolymers along with theincreasing electric field

with the molecules P1 and P2 and this trend is consistentwith the change of band gaps In addition the effects of theexternal electric field on the optical and electronic propertieswere investigated and it was found that energy level andabsorption were changed by the changed external electricfield Evaluation of higher open circuit voltage suggested thatthe 119864HOMO of P3 and Pb are lower than that of P1 and P2molecules meaning that the increased conjugated length canobtain relatively higher open circuit voltage However theresult of charge transport parameters showed that amongfour molecules the injection capability of hole of P2 ishigher and the injection capability of electron of Pb is higherThe hole transport ability of P3 and Pb is weaker thanthat of P2 from the calculation of reorganization energyTherefore it is important to simultaneously increase theoptical absorption and improve the charge transport abilityof [(benzodithiophene-26-diyl)(25-thienylene)] for furthermolecular design in the field of solar cells

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the Fundamental ResearchFunds for the Central Universities (Grant no 2572014CB31)the Heilongjiang Provincial Youth Science Foundation(Grant no QC2013C006) and the National Natural ScienceFoundation of China (Grants nos 11404055 and 11374353)

References

[1] A R Murphy and J M J Frechet ldquoOrganic semiconductingoligomers for use in thin film transistorsrdquo Chemical Reviewsvol 107 no 4 pp 1066ndash1096 2007

[2] S Beaupre J Dumas andM Leclerc ldquoToward the developmentof new textileplastic electrochromic cells using triphenylam-ine-based copolymersrdquo Chemistry of Materials vol 18 no 17pp 4011ndash4018 2006


[3] Y-J Cheng S-H Yang and C-S Hsu ldquoSynthesis of conjugatedpolymers for organic solar cell applicationsrdquo Chemical Reviewsvol 109 no 11 pp 5868ndash5923 2009

[4] X F Liu Y M Sun B B Y Hsu et al ldquoDesign and propertiesof intermediate-sized narrow band-gap conjugated moleculesrelevant to solution-processed organic solar cellsrdquo Journal of theAmerican Chemical Society vol 136 no 15 pp 5697ndash5708 2014

[5] H Meier ldquoConjugated oligomers with terminal donor-acceptorsubstitutionrdquo Angewandte ChemiemdashInternational Edition vol44 no 17 pp 2482ndash2506 2005

[6] D M Guldi and M Prato ldquoExcited-state properties of C60fullerene derivativesrdquoAccounts of Chemical Research vol 33 no10 pp 695ndash703 2000

[7] ZHe C Zhong XHuang et al ldquoSimultaneous enhancement ofopen-circuit voltage short-circuit current density and fill factorin polymer solar cellsrdquo Advanced Materials vol 23 no 40 pp4636ndash4643 2011

[8] H-S Kim C-R Lee J-H Im et al ldquoLead iodide perovskitesensitized all-solid-state submicron thin film mesoscopic solarcell with efficiency exceeding 9rdquo Scientific Reports vol 2article 591 2012

[9] J You C-C Chen Z Hong et al ldquo102 power conversionefficiency polymer tandem solar cells consisting of two identicalsub-cellsrdquo Advanced Materials vol 25 no 29 pp 3973ndash39782013

[10] J A Love I Nagao Y Huang et al ldquoSilaindacenodithiophene-based molecular donor morphological features and use in thefabrication of compositionally tolerant high-efficiency bulkheterojunction solar cellsrdquo Journal of the American ChemicalSociety vol 136 no 9 pp 3597ndash3606 2014

[11] B AGregg ldquoExcitonic solar cellsrdquo Journal of Physical ChemistryB vol 107 no 20 pp 4688ndash4698 2003

[12] H Zeng X C Zhu Y Y Liang and X G Guo ldquoInterfacial layerengineering for performance enhancement in polymer solarcellsrdquo Polymers vol 7 no 2 pp 333ndash372 2015

[13] J W P Hsu and M T Lloyd ldquoOrganicinorganic hybrids forsolar energy generationrdquo MRS Bulletin vol 35 no 6 pp 422ndash428 2010

[14] D Mori H Benten I Okada H Ohkita and S Ito ldquoLow-bandgap donoracceptor polymer blend solar cells with effi-ciency exceeding 4rdquo Advanced Energy Materials vol 4 no 3Article ID 1301006 2014

[15] K C CW S Klider F S Santos LO Peres KWohnrath and JR Garcia ldquoElectrochemical synthesis of the copolymer poly(2-methoxy-5-bromo-p-phenylenevinylene)(25-dicyano-p-phe-nylenevinylene) (MB-PPVDCN-PPV) tuning propertiesrdquoJournal of the Brazilian Chemical Society vol 25 no 3 pp572ndash578 2014

[16] J-H Kim C E Song B Kim I-N Kang W S Shin and D-HHwang ldquoThieno[32-b]thiophene-substituted benzo[12-b45-b1015840]dithiophene as a promising building block for low bandgapsemiconducting polymers for high-performance single andtandem organic photovoltaic cellsrdquo Chemistry of Materials vol26 no 2 pp 1234ndash1242 2014

[17] M Yu L Zhang Q Peng H Zhao and J Gao ldquoNarrow-bandgap Benzodipyrrolidone (BDPD) based donor conjugated poly-mer a theoretical investigationrdquoComputational andTheoreticalChemistry vol 1055 pp 88ndash93 2015

[18] S Narayanana S P Raghunathana SMathewb et al ldquoSynthesisand third-order nonlinear optical properties of low band gap34-ethylenedioxythiophene-quinoxaline copolymersrdquo Euro-pean Polymer Journal vol 64 pp 157ndash169 2015

[19] Z F Tan I Imae K Komaguchi Y Ooyama J Ohshita and YHarima ldquoEffects of 120587-conjugated side chains on properties andperformances of photovoltaic copolymersrdquo Synthetic Metalsvol 187 no 1 pp 30ndash36 2014

[20] P Hohenberg and W Kohn ldquoInhomogeneous electron gasrdquoPhysical Review vol 136 pp B864ndashB871 1964

[21] W Kohn and L J Sham ldquoQuantum density oscillations in aninhomogeneous electron gasrdquo Physical Review vol 137 no 6pp A1697ndashA1705 1965

[22] A D Becke ldquoDensity-functional exchange-energy approxima-tion with correct asymptotic behaviorrdquo Physical Review A vol38 no 6 pp 3098ndash3100 1988

[23] A D Becke ldquoDensity-functional thermochemistry I Theeffect of the exchange-only gradient correctionrdquoThe Journal ofChemical Physics vol 96 no 3 p 2155 1992

[24] C Lee W Yang and R G Parr ldquoDevelopment of the Colle-Salvetti correlation-energy formula into a functional of theelectron densityrdquo Physical Review B vol 37 no 2 pp 785ndash7891988

[25] M J Frish G W Trucks H B Schlegel et al Gaussian 09Revision A02 Gaussian Waiilingford Conn USA 2009

[26] M Sun and H Xu ldquoDirect visualization of the chemical mech-anism in SERRS of 4-aminothiophenolmetal complexes andmetal4-aminothiophenolmetal junctionsrdquo ChemPhysChemvol 10 no 2 pp 392ndash399 2009

[27] Y Z Li T Pullerits M Y Zhao and M T Sun ldquoTheoreticalcharacterization of the PC60BM PDDTTmodel for an organicsolar cellrdquo Journal of Physical Chemistry C vol 115 no 44 pp21865ndash21873 2011

[28] P Song Y Z Li F C Ma T Pullerits and M T Sun ldquoExternalelectric field-dependent photoinduced charge transfer in adonor-acceptor system for an organic solar cellrdquo Journal ofPhysical Chemistry C vol 117 no 31 pp 15879ndash15889 2013

[29] X M Zhao and M D Chen ldquoDFT study on the influenceof electric field on surface-enhanced Raman scattering frompyridinendashmetal complexrdquo Journal of Raman Spectroscopy vol45 no 1 pp 62ndash67 2014

[30] E K U Gross andW Kohn ldquoLocal density-functional theory offrequency-dependent linear responserdquo Physical Review Lettersvol 55 no 26 pp 2850ndash2852 1985

[31] T Yanai D P Tew and N C Handy ldquoA new hybrid exchange-correlation functional using the Coulomb-attenuating method(CAM-B3LYP)rdquo Chemical Physics Letters vol 393 no 1ndash3 pp51ndash57 2004

[32] M C Scharber D Muhlbacher M Koppe et al ldquoDesign rulesfor donors in bulk-heterojunction solar cellsmdashtowards 10energy-conversion efficiencyrdquo Advanced Materials vol 18 no6 pp 789ndash794 2006

[33] C-G Zhan J A Nichols and D A Dixon ldquoIonization poten-tial electron affinity electronegativity hardness and electronexcitation energymolecular properties fromdensity functionaltheory orbital energiesrdquo The Journal of Physical Chemistry Avol 107 no 20 pp 4184ndash4195 2003

[34] G Zhang and C B Musgrave ldquoComparison of DFT methodsfor molecular orbital eigenvalue calculationsrdquo Journal of Physi-cal Chemistry A vol 111 no 8 pp 1554ndash1561 2007

[35] R A Marcus ldquoElectron transfer reaction in chemistry theoryand expermentrdquo Angewandte Chemie International Edition vol32 pp 1111ndash1121 1993

[36] R AMarcus and N Sutin ldquoElectron transfers in chemistry andbiologyrdquo Biochimica et Biophysica Acta vol 811 no 3 pp 265ndash322 1985


[37] X-Y Li J Tong and F-C He ldquoAb initio calculation for innerreorganization energy of gasphase electron transfer in organicmolecule-ion systemsrdquo Chemical Physics vol 260 no 3 pp283ndash294 2000

[38] J Calvo-Castro C J McHugh and A J McLean ldquoTorsionalangle dependence and switching of inner sphere reorganisationenergies for electron and hole transfer processes involvingphenyl substituted diketopyrrolopyrroles a density functionalstudyrdquo Dyes and Pigments vol 113 pp 609ndash617 2015

[39] H Imahori H Yamada D M Guldi et al ldquoComparison ofreorganization energies for intra- and intermolecular electrontransferrdquo Angewandte ChemiemdashInternational Edition vol 41no 13 pp 2344ndash2347 2002

[40] D P McMahon and A Troisi ldquoEvaluation of the external reor-ganization energy of polyacenesrdquo Journal of Physical ChemistryLetters vol 1 no 6 pp 941ndash946 2010

[41] J-L Bredas D Beljonne V Coropceanu and J CornilldquoCharge-transfer and energy-transfer processes in 120587-conjugat-ed oligomers and polymers a molecular picturerdquo ChemicalReviews vol 104 no 11 pp 4971ndash5003 2004

[42] B A Gregg ldquoInterfacial processes in the dye-sensitized solarcellrdquo Coordination Chemistry Reviews vol 248 no 13-14 pp1215ndash1224 2004

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


researchers havemade great efforts Mori et al [14] fabricatedlow-band gap donoracceptor polymer blend solar cellspresenting a short-circuit current density of 885mA cmminus2a fill factor of 055 an open circuit voltage of 084V andthe high PCE of 4 which demonstrates the potentialof polymerpolymer blend solar cells as an alternative topolymerfullerene solar cells Klider and coworkers [15]synthesized the copolymer poly(2-methoxy-5-bromo-p-phe-nylenevinylen)(25-dicyano-p-phenylenevinylene)(MB-PPVDCN-PPV) using an electrochemical method and the con-clusions by cyclic voltammetry (CV) UV-Vis and fluo-rescence (FL) spectroscopy showed that the conduction bandis more stabilized in the copolymer than in homo polymerKim et al [16] designed and synthesized a new poly48-bis((2-ethylhexyl)thieno [32-b]thiophene)-benzo[12-b45-b1015840]dithiophene-alt-2-ethylhexyl-46-dibromo-3-fluorothieno[34-b]thiophene-2-carboxylate (PTTBDT-FTT) and anorganic thin-film transistor showed high hole mobility of 21times 10minus2 cm2(Vsdots) and they also fabricated a single-junctionbulk heterojunction photovoltaic cells inverted photovol-taic cells and a tandem photovoltaic device comprisingPTTBDT-FTT showing a maximum power conversionefficiency (PCE) of 744 771 and 866 respectively Inaddition researchers also have committed to design novelactive layer materials with low-band gaps and high carriermobility Yu and coworkers [17] designed four new D-Acopolymers PCDT-BDPD (P1b) PDTC-BDPPD (P2b)PBDTTF-BDPD (P3b) and PBDTF-BDPD (P4b) based ondiketopyrrolopyrrole (DPP) polymers and the predictedPCEs of the new donor polymers reached up to about 10in theory Narayanana et al [18] designed and synthesized aseries of 34-ethylenedioxy thiophene (EDOT) and quinox-aline donor-acceptor (D-A) copolymers P(EDOT-ACEQX)P(EDOT-BZQX) and P(EDOT-PHQX) exhibiting electro-chemical band gap of 105 10 and 099 eV respectively

In this work density function theory (DFT) was usedto study three types of copolymers [19] a copolymer con-taining BDT and thiophene units in the main chain (noconjugated side-chain) and the copolymer is abbreviated asP1 introducing a conjugated side chain with no electron-withdrawing group into P1 which was named after P2introducing a side chain with an electron-withdrawing groupinto P1 which was named after P3 Optical electrochemicaland photovoltaic properties of P1 P2 and P3 were studied(see Figure 1) they are compared with those of a main chaintype copolymer PBDT-BTA to get an insight into the effectof the introduction of conjugated side chain on photovoltaicproperties of the conjugated copolymers

2 Computational Methods

The molecular geometries of the several oligomers P1 P2P3 and Pb (119899 = 1ndash3) were fully optimized using the DFT[20 21] with B3LYP functional [22ndash24] All calculationsin this work were carried out using Gaussian 09 programpackage [25] The 6-31G (d) basis set was used for allcalculations The HOMO LUMO and gap (HOMO-LUMO)energies were also deduced for the stable structures and

electron density corresponding to energy levels was studiedIt is worth noting that DFT gives Kohn-Sham orbitals notmolecular orbitals which uses the KS orbitals to approximatethe properties of the HOMO and LUMO DFT combinedwith electron density analysis has been successful to inves-tigate several series of polymers and charge transfer processunder photon excitation [26ndash29] Reorganization energieswere obtained by means of calculation of the single pointenergy at the DFTB3LYP level6-31G(d) followed by theoptimized geometries of different states (the neutral cationicand anionic geometries) Electronic transition energies andoscillator strengths of oligomers were obtained by using timedependent density functional theory (TDDFT) [30] at theCam-B3LYP6-31G (d) level [31] which contains 65 long-range HF exchange

3 Results and Discussion

31 Structural Properties The ground state structures of P1P2 P3 and Pb were optimized using DFTB3LYP with 6-31G (d) basis set The computing values (compromising thebond lengths and dihedral angles for their tripolymers) werelisted in Table 1 and the number of atoms for the tripolymersstructure of P1 and Pb were labeled in Supporting Materials(see Figure S1 in Supplementary Material available online athttpdxdoiorg1011552015964252) and optimized carte-sian coordinates and total energies were listed in Tables S1ndashS4 Compared to the bond length at same position of P1 P2and P3 one can find the bond lengths for P3 that present thebiggest values in the three molecules and the value for P1 isthe smallest For C2-C3 the values for P1 P2 and P3 were1444 1446 and 1447 respectively It indicates that there isalmost no change upon introducing a C=C and thiopheneinto the side chain of P1 and a cyan into the side chain of P2

Moreover it can be seen in Table 1 that the averagedihedral angle of P3 is the biggest among P1 P2 and P3indicating the conjugated main chain of P3 twisted seriouslyFor example C1-C2-C3-S4 S4-C5-C6-C7 C8-C9-C10-S11S11-C12- C13-C14 and C15-C16-C17-S18 for P3 are minus151∘367∘ minus76∘ 357∘ and minus143∘ respectively and for P1 they areminus39∘ 39∘ minus75∘ 77∘ and minus91∘ respectively So the structureof ground state for P1 tends to flatten among the threemolecules But comparing P1 with Pb the average dihedralangle of Pb seemed smaller than that of P1 One can makea conclusion that introducing a side chain can change thecoplanarity at the micro level

32 HOMO LUMO and Band Gaps (Δ119867-119871) The HOMO

and LUMO energy levels and band gaps ΔH-L (differencebetween HOMO and LUMO) of the oligomers (119899 = 1 2 3)are computed and the results are given in Table 2 Moreoverthe energy levels and band gaps of the polymers are obtainedby the extrapolation As shown in Table 2 with the increasingconjugated units HOMO energy levels increased slightly andLUMO energy levels decreased obviously and the band gapsΔH-L present a decreased tendency Moreover it can be seenin Figure 2 that with the increasing of conjugatedmain chainthe HOMO energy levels of the four molecules have a tinychange but the LUMO energy levels of that change obviously






P1 P2

P3 PBDT-BTA (Pb)





119881oc = (1119890) [1003816100381610038161003816119864HOMO (119863)

1003816100381610038161003816 minus1003816100381610038161003816119864LUMO (119860)

1003816100381610038161003816] minus 03119881 (1)





P1


P2


P3


Pb


Pb

P2

P3

P1

Ener

gy le

vel (

eV)

HOMOLUMO

minus55

minus50

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10







119899 = 1 617 030 601 050 615 092 604 135119899 = 2 569 121 558 135 577 166 567 203119899 = 3 562 157 547 161 572 193 554 229119899 rarr infin 530 218 518 218 547 242 529 274







P1


P2


P3


Pb


LUMOHOMO

P1

P2

P3

Pb




120581119864119879

= 119860 exp [ minus1205824120581119861

119879] (2)


IPEA

IPEA

03 11100908070605040

1

2

3

4

5

6

P1

Ener

gy (e

V)

1n 1n

1n 1n

03 11100908070605040

1

2

3

4

5

6

P2

Ener

gy (e

V)

03 1110090807060504

1

2

3

4

5

6

P3

Ener

gy (e

V)

03 11100908070605041

2

3

4

5

6

Pb

Ener

gy (e

V)

y = minus186x + 218

R2 = 0997

y = 086x + 530

R2 = 0969

y = minus167x + 218

R2 = 0999

y = 082x + 518

R2 = 0995

y = minus151x + 242

R2 = 0999

y = 067x + 547

R2 = 0963

y = minus140x + 274

R2 = 0998

y = 075x + 529

R2 = 0999




ℎ


119890


120582119890

= (119864minus


minus1198640)

120582ℎ

= (119864+

0 minus119864+) + (1198640+

minus1198640)

(3)

where 119864+0

(119864minus0


+

(119864minus


+

(1198640minus





200 6005004003000

16

32

48

64

Abso

rptio

n

Wavelength (nm)

P1P2

P3Pb

times103

(a)

200 9008007006005004003000

60

120

180

240

Abso

rptio

n

Wavelength (nm)

times103

P1P2

P3Pb

(b)



P1 P2 P3 Pb

119899 = 1120582119890

310 245 268 287120582ℎ

467 312 382 377

119899 = 2120582119890

250 324 324 186120582ℎ

358 230 386 269

119899 = 3120582119890

192 254 255 129120582ℎ

281 198 218 185







4 Conclusion










32

1

Pb

P3

P2P1

Ener

gy le

vel (

eV)

HOMOLUMO

minus18

minus20

minus22

minus24

minus26

minus28

minus32

minus34

minus36

minus38

minus30

minus42

minus44

minus46

minus48

minus40

minus50


10 30252015

020406081012141618202224262830

Ener

gy g

ap (e

V)

P1P2

P3Pb

F (10minus3 au)





Acknowledgments


References






















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of






P1 P2

P3 PBDT-BTA (Pb)





119881oc = (1119890) [1003816100381610038161003816119864HOMO (119863)

1003816100381610038161003816 minus1003816100381610038161003816119864LUMO (119860)

1003816100381610038161003816] minus 03119881 (1)





P1


P2


P3


Pb


Pb

P2

P3

P1

Ener

gy le

vel (

eV)

HOMOLUMO

minus55

minus50

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10







119899 = 1 617 030 601 050 615 092 604 135119899 = 2 569 121 558 135 577 166 567 203119899 = 3 562 157 547 161 572 193 554 229119899 rarr infin 530 218 518 218 547 242 529 274







P1


P2


P3


Pb


LUMOHOMO

P1

P2

P3

Pb




120581119864119879

= 119860 exp [ minus1205824120581119861

119879] (2)


IPEA

IPEA

03 11100908070605040

1

2

3

4

5

6

P1

Ener

gy (e

V)

1n 1n

1n 1n

03 11100908070605040

1

2

3

4

5

6

P2

Ener

gy (e

V)

03 1110090807060504

1

2

3

4

5

6

P3

Ener

gy (e

V)

03 11100908070605041

2

3

4

5

6

Pb

Ener

gy (e

V)

y = minus186x + 218

R2 = 0997

y = 086x + 530

R2 = 0969

y = minus167x + 218

R2 = 0999

y = 082x + 518

R2 = 0995

y = minus151x + 242

R2 = 0999

y = 067x + 547

R2 = 0963

y = minus140x + 274

R2 = 0998

y = 075x + 529

R2 = 0999




ℎ


119890


120582119890

= (119864minus


minus1198640)

120582ℎ

= (119864+

0 minus119864+) + (1198640+

minus1198640)

(3)

where 119864+0

(119864minus0


+

(119864minus


+

(1198640minus





200 6005004003000

16

32

48

64

Abso

rptio

n

Wavelength (nm)

P1P2

P3Pb

times103

(a)

200 9008007006005004003000

60

120

180

240

Abso

rptio

n

Wavelength (nm)

times103

P1P2

P3Pb

(b)



P1 P2 P3 Pb

119899 = 1120582119890

310 245 268 287120582ℎ

467 312 382 377

119899 = 2120582119890

250 324 324 186120582ℎ

358 230 386 269

119899 = 3120582119890

192 254 255 129120582ℎ

281 198 218 185







4 Conclusion










32

1

Pb

P3

P2P1

Ener

gy le

vel (

eV)

HOMOLUMO

minus18

minus20

minus22

minus24

minus26

minus28

minus32

minus34

minus36

minus38

minus30

minus42

minus44

minus46

minus48

minus40

minus50


10 30252015

020406081012141618202224262830

Ener

gy g

ap (e

V)

P1P2

P3Pb

F (10minus3 au)





Acknowledgments


References






















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




P1


P2


P3


Pb


Pb

P2

P3

P1

Ener

gy le

vel (

eV)

HOMOLUMO

minus55

minus50

minus45

minus40

minus35

minus30

minus25

minus20

minus15

minus10







119899 = 1 617 030 601 050 615 092 604 135119899 = 2 569 121 558 135 577 166 567 203119899 = 3 562 157 547 161 572 193 554 229119899 rarr infin 530 218 518 218 547 242 529 274







P1


P2


P3


Pb


LUMOHOMO

P1

P2

P3

Pb




120581119864119879

= 119860 exp [ minus1205824120581119861

119879] (2)


IPEA

IPEA

03 11100908070605040

1

2

3

4

5

6

P1

Ener

gy (e

V)

1n 1n

1n 1n

03 11100908070605040

1

2

3

4

5

6

P2

Ener

gy (e

V)

03 1110090807060504

1

2

3

4

5

6

P3

Ener

gy (e

V)

03 11100908070605041

2

3

4

5

6

Pb

Ener

gy (e

V)

y = minus186x + 218

R2 = 0997

y = 086x + 530

R2 = 0969

y = minus167x + 218

R2 = 0999

y = 082x + 518

R2 = 0995

y = minus151x + 242

R2 = 0999

y = 067x + 547

R2 = 0963

y = minus140x + 274

R2 = 0998

y = 075x + 529

R2 = 0999




ℎ


119890


120582119890

= (119864minus


minus1198640)

120582ℎ

= (119864+

0 minus119864+) + (1198640+

minus1198640)

(3)

where 119864+0

(119864minus0


+

(119864minus


+

(1198640minus





200 6005004003000

16

32

48

64

Abso

rptio

n

Wavelength (nm)

P1P2

P3Pb

times103

(a)

200 9008007006005004003000

60

120

180

240

Abso

rptio

n

Wavelength (nm)

times103

P1P2

P3Pb

(b)



P1 P2 P3 Pb

119899 = 1120582119890

310 245 268 287120582ℎ

467 312 382 377

119899 = 2120582119890

250 324 324 186120582ℎ

358 230 386 269

119899 = 3120582119890

192 254 255 129120582ℎ

281 198 218 185







4 Conclusion










32

1

Pb

P3

P2P1

Ener

gy le

vel (

eV)

HOMOLUMO

minus18

minus20

minus22

minus24

minus26

minus28

minus32

minus34

minus36

minus38

minus30

minus42

minus44

minus46

minus48

minus40

minus50


10 30252015

020406081012141618202224262830

Ener

gy g

ap (e

V)

P1P2

P3Pb

F (10minus3 au)





Acknowledgments


References






















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




P1


P2


P3


Pb


LUMOHOMO

P1

P2

P3

Pb




120581119864119879

= 119860 exp [ minus1205824120581119861

119879] (2)


IPEA

IPEA

03 11100908070605040

1

2

3

4

5

6

P1

Ener

gy (e

V)

1n 1n

1n 1n

03 11100908070605040

1

2

3

4

5

6

P2

Ener

gy (e

V)

03 1110090807060504

1

2

3

4

5

6

P3

Ener

gy (e

V)

03 11100908070605041

2

3

4

5

6

Pb

Ener

gy (e

V)

y = minus186x + 218

R2 = 0997

y = 086x + 530

R2 = 0969

y = minus167x + 218

R2 = 0999

y = 082x + 518

R2 = 0995

y = minus151x + 242

R2 = 0999

y = 067x + 547

R2 = 0963

y = minus140x + 274

R2 = 0998

y = 075x + 529

R2 = 0999




ℎ


119890


120582119890

= (119864minus


minus1198640)

120582ℎ

= (119864+

0 minus119864+) + (1198640+

minus1198640)

(3)

where 119864+0

(119864minus0


+

(119864minus


+

(1198640minus





200 6005004003000

16

32

48

64

Abso

rptio

n

Wavelength (nm)

P1P2

P3Pb

times103

(a)

200 9008007006005004003000

60

120

180

240

Abso

rptio

n

Wavelength (nm)

times103

P1P2

P3Pb

(b)



P1 P2 P3 Pb

119899 = 1120582119890

310 245 268 287120582ℎ

467 312 382 377

119899 = 2120582119890

250 324 324 186120582ℎ

358 230 386 269

119899 = 3120582119890

192 254 255 129120582ℎ

281 198 218 185







4 Conclusion










32

1

Pb

P3

P2P1

Ener

gy le

vel (

eV)

HOMOLUMO

minus18

minus20

minus22

minus24

minus26

minus28

minus32

minus34

minus36

minus38

minus30

minus42

minus44

minus46

minus48

minus40

minus50


10 30252015

020406081012141618202224262830

Ener

gy g

ap (e

V)

P1P2

P3Pb

F (10minus3 au)





Acknowledgments


References






















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


IPEA

IPEA

03 11100908070605040

1

2

3

4

5

6

P1

Ener

gy (e

V)

1n 1n

1n 1n

03 11100908070605040

1

2

3

4

5

6

P2

Ener

gy (e

V)

03 1110090807060504

1

2

3

4

5

6

P3

Ener

gy (e

V)

03 11100908070605041

2

3

4

5

6

Pb

Ener

gy (e

V)

y = minus186x + 218

R2 = 0997

y = 086x + 530

R2 = 0969

y = minus167x + 218

R2 = 0999

y = 082x + 518

R2 = 0995

y = minus151x + 242

R2 = 0999

y = 067x + 547

R2 = 0963

y = minus140x + 274

R2 = 0998

y = 075x + 529

R2 = 0999




ℎ


119890


120582119890

= (119864minus


minus1198640)

120582ℎ

= (119864+

0 minus119864+) + (1198640+

minus1198640)

(3)

where 119864+0

(119864minus0


+

(119864minus


+

(1198640minus





200 6005004003000

16

32

48

64

Abso

rptio

n

Wavelength (nm)

P1P2

P3Pb

times103

(a)

200 9008007006005004003000

60

120

180

240

Abso

rptio

n

Wavelength (nm)

times103

P1P2

P3Pb

(b)



P1 P2 P3 Pb

119899 = 1120582119890

310 245 268 287120582ℎ

467 312 382 377

119899 = 2120582119890

250 324 324 186120582ℎ

358 230 386 269

119899 = 3120582119890

192 254 255 129120582ℎ

281 198 218 185







4 Conclusion










32

1

Pb

P3

P2P1

Ener

gy le

vel (

eV)

HOMOLUMO

minus18

minus20

minus22

minus24

minus26

minus28

minus32

minus34

minus36

minus38

minus30

minus42

minus44

minus46

minus48

minus40

minus50


10 30252015

020406081012141618202224262830

Ener

gy g

ap (e

V)

P1P2

P3Pb

F (10minus3 au)





Acknowledgments


References






















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


200 6005004003000

16

32

48

64

Abso

rptio

n

Wavelength (nm)

P1P2

P3Pb

times103

(a)

200 9008007006005004003000

60

120

180

240

Abso

rptio

n

Wavelength (nm)

times103

P1P2

P3Pb

(b)



P1 P2 P3 Pb

119899 = 1120582119890

310 245 268 287120582ℎ

467 312 382 377

119899 = 2120582119890

250 324 324 186120582ℎ

358 230 386 269

119899 = 3120582119890

192 254 255 129120582ℎ

281 198 218 185







4 Conclusion










32

1

Pb

P3

P2P1

Ener

gy le

vel (

eV)

HOMOLUMO

minus18

minus20

minus22

minus24

minus26

minus28

minus32

minus34

minus36

minus38

minus30

minus42

minus44

minus46

minus48

minus40

minus50


10 30252015

020406081012141618202224262830

Ener

gy g

ap (e

V)

P1P2

P3Pb

F (10minus3 au)





Acknowledgments


References






















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of









32

1

Pb

P3

P2P1

Ener

gy le

vel (

eV)

HOMOLUMO

minus18

minus20

minus22

minus24

minus26

minus28

minus32

minus34

minus36

minus38

minus30

minus42

minus44

minus46

minus48

minus40

minus50


10 30252015

020406081012141618202224262830

Ener

gy g

ap (e

V)

P1P2

P3Pb

F (10minus3 au)





Acknowledgments


References






















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




















































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Research Article Spectra and Charge Transport of Polar ...

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