Current through Current through electronic deviceelectronic device

Dynamics of electronic Dynamics of electronic carrierscarriers

J = nevd = ne2F/m* J = F (lei de Ohm)  

= ne2/m* = ne      

vd = F

= e/m*        

= e(nee + npp)

meFvdt

dd /

r

NON-LINEAR EFFECTS ON THE NON-LINEAR EFFECTS ON THE MOBILITYMOBILITY

Space-charge limited current

J (9/8)V2/l3

**********************************************

Poole-Frenkel effect

J = ne(E)E

with

Capacitor – Electric FieldCapacitor – Electric Field

Dielectrics - PolarizationDielectrics - Polarization

Dipole MomentDipole Moment

= 2a

DEVICE 3: OTFTsOrganic Thin-Film Transistors

DEVICE 2: OLEDsOrganic Light-Emitting Diodes

DEVICE 1: OPVsOrganic Photovoltaics

DEVICE 1: DEVICE 1: OPVOPVOOrganic rganic PPhotohotovvoltaicsoltaics

Generations of Solar Cells

First: PV p-n junction diode of crystalline silicon (market)

Second: PV thin films of non-monocrystalline semiconductors(amorphous silicon, poly-crystalline silicon, cadmium

telluride films, copper indium selenide/sulfide,...) (market)

Third: Organic photovoltaic cells, photoelectrochemical cells, dye-sensitized Solar cells,...) (research)

Fourth: Biomolecular cells (prevision) - Mimicking the nature.

MARKETMARKET

P V T e c h n o l o g y P VG e n e r a t i o n

F o r e c a s t t i m e f r o m m a r k e ta c c e p t a n c e t o d e c l i n e

S i l i c o n C r y s t a l l i n e 1 1 9 7 0 - 2 0 2 0S i l i c o n A m o r p h o u s 2 1 9 8 3 - 2 0 2 5S i l i c o n T h i n F i l m 2 2 0 0 1 - 2 0 5 0C d T e 2 1 9 9 5 - 2 0 1 0C I S / C I G S o t h e r 3 / 5 , 2 / 4 / 6 2 2 0 0 0 - 2 0 5 0D S C 3 2 0 0 3 - 2 0 5 5D S C - h y b r i d 3 + 2 0 1 5 - 2 1 0 0O r g a n i c - h y b r i d 3 + 2 0 1 5 - 2 1 0 0B i o l o g i c a l 4 2 0 3 0 - 2 1 0 0 +

A c t u a l o r f o r e c a s t m a r k e t a c c e p t a n c e t o m a r k e t d e c l i n e f o r t h e i m p o r t a n t P V t e c h n o l o g i e s

T i m i n g

Sun: Total Sun: Total powerpower

0

/inP A F hc d

Organic materialAbsorption

Equivalent circuit and characteristic curve

Isc ..... Short-circuit currentVoc .... Open-circuit voltage

Imp .... Current at maximum powerVmp .... Voltage at maximum power

Fill Factor

FF = (Vmp x Imp)/(Voc x Isc)

Current sourceDiodeRc (contact + bulk) resistancesRs shunt resistance

.out mp mp ca ccP V I FF V I

EFFICIENCY

EfficiencyEfficiency

Quantum efficiency: ratio of the number of collected chargecarriers to the number of incident photons (EQE or IPCE).

Power Conversion Energy (PCE):ratio between the solar power produced by the cell by the power of the incidente flux of light

First generation: pn JUNCTION

Thickness 100 m

Second generation: Inorganic Heterojunction

Thickness 5 m

Third generation: Organics

ELECTRONIC DEFECTS

Poly(p-phenylene) - PPP

Charge Charge spinspin

exciton singlet 0 0

Negative polaron - e 1/2

Positive polaron e 1/2

Negative bipolaron - 2e 0

Positive bipolaron 2e 0

In organic semiconductor the generation of carriers is a secondary process. Excitons (bound electron-hole pairs) are created by absorption of light, and should be dissociated, and then the carriers collected by electrodes)

HETEROJUNCTION

Thickness < 100 nm

2.5 % Efficient Organic Plastic Solar Cells

S. E. Shaheen et al, Appl. Phys. Lett 78, 841 (2001)

First High EfficiencyFirst High Efficiency

Dispersed electronegative species

Poly(disilanyleneoligothienylene) + CPoly(disilanyleneoligothienylene) + C6060

Onsager effectOnsager effect

kTr

e

o

4

2

T = 300 K = 3 r 20 nm

An electric field of the order of 105 V/cm already stimulatesthe dissociation mechanism

High Efficiency Cell (4.2 %)High Efficiency Cell (4.2 %)

4.2 % Efficient Organic PV Cells Wtih Low Series ResistancesJ. Xue et al, Appl. Phys. Lett. 84, 3013 (2004)

Double heterostructure20 nm donor-like layer-CuPc40 nm acceptor-like layer-C60

10 nm exciton-blocking layer of bathocuproine (BCP)

High efficiency cell (4.6 %)High efficiency cell (4.6 %)

Poly(ethylenedioxythiophene):polystyrenesulfonatePoly(3-hexylthiophene-2,5-diyl):[6,6]-phenil-C61-butyric acid methyl esterCopper phthalocyanine:fullerene

High efficient organic tandem solar cells using naimproved connecting architecture

A.G. F. Janseen et al, Appl. Phys. Lett. 91, 073519 (2007)

Donor-acceptor mixture

Important characteristicsImportant characteristics

Characteristics of OPV:

High absorption coefficient (10-5 cm-1)Short penetration depthThin films (10 – 1000 nm)

Important limitation for organic PV isthe short diffusion length of the exciton

To mentionTo mention

Electrochemical Solar CellElectrochemical Solar Cell

Summary

OPV End

DEVICE 2: OLEDsOrganic Ligth-Emittng Diodes

Polymers and Small MoleculesPLEDs and SMOLEDs

Most important luminescent polymers

Poly(p-phenylene vinylene)

Polyfluorene

Most important luminescent small molecules

ALq3 Pentacene derivatives

Most important electrical Most important electrical and optical characteristicsand optical characteristics

IV curves IV curves

ITO/PPV/Al ITO/MH-PPV/Al

Current vs LuminescenceCurrent vs Luminescence

40 45 500

1

2

3

4

T = 20 K

Intensidade Luminosa (U

.A.)

Corrente

Cor

rent

e (m

A)

Voltagem (V)

Intensidade luminosa

JABLONSKI DIAGRAMJABLONSKI DIAGRAM

Absorption and Emission (molecules)Frank-Condon Efeect

Absorption and Emission Absorption and Emission of PPVof PPV

200 300 400 500 600 700 800

Comprimento de onda (nm)

PL

(u

.a.)

547 nm

437 nm

Ab

sorção (

u.a

.)

Photo and Electroluminescent emissionPhoto and Electroluminescent emission

480 510 540 570 600 630 660 690

Comprimento de Onda (nm)

P1= (//) e P

2 = (//)

P1= () e P

2 = ()

Inte

nsid

ade

de E

mis

são

(u.a

)

Detecteur0º

180º

90º

Analisateur

P1 (//)

S-Film

P1 ()

Laser

Optical system to detect polarized photoluminescence

Disordered PPV Film

0 60 120 180 240 300 360

0,2

0,4

0,6

0,8

1,0

1,2

1,4

P1(//)P1()

Inte

nsid

ade

de E

mis

são

Nor

mal

iz. (

u.a.

)

Ângulo do Analisador P2 (Grad)

0 60 120 180 240 300 360

0,2

0,4

0,6

0,8

1,0

1,2

1,4

0 60 120 180 240 300 360

0,2

0,4

0,6

0,8

1,0

1,2

1,4

P1(//)P1()

Inte

nsid

ade

de E

mis

são

Nor

mal

iz. (

u.a.

)

Ângulo do Analisador P2 (Grad)

0 60 120 180 240 300 360

0,4

0,6

0,8

1,0

1,2

P1(//)P1()

Inte

nsid

ade

de E

mis

são

Nor

mal

iz.(

u.a.

)

Ângulo do Analisador (Grad)

0 60 120 180 240 300 360

0,4

0,6

0,8

1,0

1,2

0 60 120 180 240 300 360

0,4

0,6

0,8

1,0

1,2

P1(//)P1()

Inte

nsid

ade

de E

mis

são

Nor

mal

iz.(

u.a.

)

Ângulo do Analisador (Grad)

Stretched PPV Film

Stretched PPVStretched PPV

-50 0 50 100 150 200 250 300 350 400

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

4.0 mm A

A

Inte

ns

ida

de

(u

.a)

Ângulo (graus)

-50 0 50 100 150 200 250 300 350 400

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4 3.5 mm A

AIn

ten

sid

ad

e (

u.a

.)

Ângulo (u.a.)

-50 0 50 100 150 200 250 300 350 4000.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.43.0 mm

A

A

Inte

ns

ida

de

(u

.a.)

Ângulo (graus)

-50 0 50 100 150 200 250 300 350 4000.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4 2.5 mm A

A

Inte

ns

ida

de

(u

.a.)

Ângulo (graus)

-50 0 50 100 150 200 250 300 350 4000.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4 2.0 mm A

A

Inte

ns

ida

de

(u

.a.)

Ângulo (graus)

-50 0 50 100 150 200 250 300 350 400

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

A

A

Inte

ns

ida

de

(u

.a.)

Ângulo (graus)

1.0 mm

-50 0 50 100 150 200 250 300 350 4000.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4 1.5 mm A

A

Inte

ns

ida

de

(u

.a.)

Angulo (graus)

-50 0 50 100 150 200 250 300 350 4000.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

Inte

ns

ida

de

(u

..a

)

Ângulo (graus)

A

A

0.0 mm

Electronic Model and Distribution of conjugation lenght PPV

(a) (b)(a) (b)

TECHNOLOGYTECHNOLOGY

PLEDs – Blue and WhitePLEDs – Blue and White

Ink Jet Printing ProcessInk Jet Printing Process

Ink-Jet Printer Heads

PLEDs are solution processable, and can be appliedusing ink jet printing processes

Printers

Technological Advances of OLEDs

Future? No, present!Future? No, present!

Comparison OLED-LCDComparison OLED-LCD

Light Diffuser

Prism Sheet

Polarizer Film

Common Electrode

Protective Film

Glass Substrate

Waveguide Plate

Back Light

Reflector

Polarizer Film

Black Matrix

Color Filter

Capacitor

Alignment Film

Liquid CrystalSpace

r

Sealant

7mm Typica

l

TFT-LCD

Potentially, up to 50% of the display cost is eliminated

P-OLED devices can reduce

costs significantly:

No backlight unit

No liquid crystal light

valve

No color filter

Simpler bill of

materials

Simpler production

method

Display Electrode

Glass Substrate

2mm Typica

l

Cathode

Anode (ITO)

Glass Substrate

P-OLED

Glass Substrate

Polarizer Film

Emissive Layer

Interlayer

Hole Conducting Polymer

200nm

White OLED (Organic White OLED (Organic Lighting)Lighting)