Solvent Vapor Annealing to Improve BiI3 PV Thin …Deposition BiI 3 Solution Deposition Thermal...
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ABSTRACT The use of dimethylformamide (DMF) as a solvent in vapor annealing processing has been previously shown to improve the device performance of bismuth triiodide (BiI 3 ) photovoltaics. An extension of this work is to integrate dimethylysulfoxide (DMSO) as a solvent in the vapor annealing processing to further improve BiI 3 thin film morphology. The use of DMSO led to larger grain sizes compared to DMF, however, voids in the film at the expense of larger grains led to a decrease in the J SC of BiI 3 photovoltaics (PVs). A 1:1 mixture of DMF and DMSO was found to improve the J SC of BiI 3 PV devices. The material presented here is based upon work supported by the National Science Foundation under Award No. EEC-0813570 and EEC-1406296. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Solvent Vapor Annealing to Improve BiI 3 PV Thin-Film Morphology Gil P. Baguio, Chemical and Biological Engineering Department, Iowa State University REFERENCES [1] Hamdeh et al. (2016). Solution-Processed BiI 3 Thin Films for Photovoltaic Applications: Improved Charge Transport via Solvent Annealing, submitted. [2] Grob et al. (2015). Solvent Vapor Annealing on Perylene-Based Organic Solar Cells. Journal of Materials Chemistry A, pp. 15700-15709. [3] Miller et al. (2007). Investigation of Nanoscale Morphological Changes in Organic Photovoltaics during Solvent Vapor Annealing. Journal of Material Chemistry, pp. 306-312. RESULTS & GRAPHICS/CHARTS BACKGROUND METHODS ACKNOWLEDGEMENT A special thanks to Dr. Matthew Panthani, my faculty mentor, Umar Hamdeh and Rainie Nelson, my graduate mentors, Brad Ryan, and the RET fellowship staff. DISCUSSION Solvent vapor annealing (SVA) has been a widely used strategy to improve film quality, increase grain size, and enhance carrier transport. 1-3 Solvent vapor annealing with DMSO was found to significantly improve the crystal grain size of BiI 3 thin films compared to using DMF. The increase in crystal grain size was at the expense of voids formed in the thin film resulting in a decrease in BiI 3 PV device performance. Voids in the film lead to poor charge transport in the BiI 3 PV devices, specifically seen as a decrease in J SC shown in Figure 3. A 1:1 mixture of DMF and DMSO results in both an increase in BiI 3 crystal grain size, and in uniform film coverage – alleviating the issue with voids in the thin film increasing charge transport. However this processing condition also led to the lowest V OC of all PV devices tested. Figure 2 shows the current-voltage characteristics of BiI 3 PVs. Low fill factors are a result of decreased shunt resistance which arises from SVA processing. 1 Fig.2 J-V sweeps of BiI 3 PVs processed with DMF and DMSO solvent vapor annealing Fig.3 The effect of the percentage of DMSO in the solvent on the J SC and V OC of BiI 3 PV devices Fig.1 SEM images of BiI 3 thin films processed with DMF and DMSO solvent vapor annealing BiI 3 has recently gained interest as a nontoxic alternative to lead-based hybrid perovskite photovoltaics. The material has a bandgap of ~1.8 eV making it suitable for use in a single junction solar cell, or as the top layer of a tandem solar cell. Recently, Hamdeh et al. 1 demonstrated a BiI 3 PV device with greater than 1% efficiency utilizing solvent vapor annealing techniques to improve grain size and film morphology to improve charge carrier mobility. FTO Glass Preparation TiO 2 Solution Deposition BiI 3 Solution Deposition Thermal Evaporation of V 2 O 5 and Au Device Testing Solvent Vapor Annealing 1) Spin coat BiI 3 into a glass substrate with TiO 2 2) Place spin coated BiI 3 onto a preheated (160 ºC) aluminum block (160 ºC) for 30 seconds 3) 10 µL of solvent (DMF and/or DMSO) was placed on the aluminum next to the BiI 3 and both were covered with a petri dish for 10 minutes 4) The petri dish was removed, and the BiI 3 was thermally annealed for 20 minutes
Transcript of Solvent Vapor Annealing to Improve BiI3 PV Thin …Deposition BiI 3 Solution Deposition Thermal...
ABSTRACTThe use of dimethylformamide (DMF) as a solvent in vapor annealing processing has beenpreviously shown to improve the device performance of bismuth triiodide (BiI3)photovoltaics. An extension of this work is to integrate dimethylysulfoxide (DMSO) as asolvent in the vapor annealing processing to further improve BiI3 thin film morphology.The use of DMSO led to larger grain sizes compared to DMF, however, voids in the film atthe expense of larger grains led to a decrease in the JSC of BiI3 photovoltaics (PVs). A 1:1mixture of DMF and DMSO was found to improve the JSC of BiI3 PV devices.
The material presented here is based upon work supported by the National Science Foundation under Award No. EEC-0813570 and EEC-1406296. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
Solvent Vapor Annealing to Improve BiI3 PV Thin-Film MorphologyGil P. Baguio, Chemical and Biological Engineering Department, Iowa State University
REFERENCES[1] Hamdeh et al. (2016). Solution-Processed BiI3 Thin Films for Photovoltaic Applications: Improved ChargeTransport via Solvent Annealing, submitted.[2] Grob et al. (2015). Solvent Vapor Annealing on Perylene-Based Organic Solar Cells. Journal of MaterialsChemistry A, pp. 15700-15709.[3] Miller et al. (2007). Investigation of Nanoscale Morphological Changes in Organic Photovoltaics duringSolvent Vapor Annealing. Journal of Material Chemistry, pp. 306-312.
RESULTS & GRAPHICS/CHARTS
BACKGROUND
METHODS
ACKNOWLEDGEMENTA special thanks to Dr. Matthew Panthani, my faculty mentor, Umar Hamdeh and Rainie Nelson,
my graduate mentors, Brad Ryan, and the RET fellowship staff.
DISCUSSIONSolvent vapor annealing (SVA) has been a widely used strategy to improve film quality, increase grain size, and enhance carrier transport.1-3 Solvent vapor annealing with DMSO was found tosignificantly improve the crystal grain size of BiI3 thin films compared to using DMF. The increase in crystal grain size was at the expense of voids formed in the thin film resulting in a decrease inBiI3 PV device performance. Voids in the film lead to poor charge transport in the BiI3 PV devices, specifically seen as a decrease in JSC shown in Figure 3. A 1:1 mixture of DMF and DMSO resultsin both an increase in BiI3 crystal grain size, and in uniform film coverage – alleviating the issue with voids in the thin film increasing charge transport. However this processing condition also led tothe lowest VOC of all PV devices tested. Figure 2 shows the current-voltage characteristics of BiI3 PVs. Low fill factors are a result of decreased shunt resistance which arises from SVA processing.1
Fig.2 J-V sweeps of BiI3 PVs processed with DMF and DMSO solvent vapor annealing
Fig.3 The effect of the percentage of DMSO in the solvent on the JSC and VOC of BiI3 PV devices
Fig.1 SEM images of BiI3 thin films processed with DMF and DMSO solvent vapor annealing
BiI3 has recently gained interest as a nontoxic alternative tolead-based hybrid perovskite photovoltaics. The material hasa bandgap of ~1.8 eV making it suitable for use in a singlejunction solar cell, or as the top layer of a tandem solar cell.Recently, Hamdeh et al.1 demonstrated a BiI3 PV device withgreater than 1% efficiency utilizing solvent vapor annealingtechniques to improve grain size and film morphology toimprove charge carrier mobility.
FTO Glass Preparation
TiO2 Solution Deposition
BiI3 Solution Deposition
Thermal Evaporation of V2O5 and Au
Device Testing
Solvent Vapor
Annealing
1) Spin coat BiI3 into a glass substrate with TiO22) Place spin coated BiI3 onto a preheated (160 ºC)
aluminum block (160 ºC) for 30 seconds3) 10 µL of solvent (DMF and/or DMSO) was
placed on the aluminum next to the BiI3 and both were covered with a petri dish for 10 minutes
4) The petri dish was removed, and the BiI3 was thermally annealed for 20 minutes
