ABSTRACTPerovskite organic hybrid solar cells degrade rapidly5. The degradation mechanism is not well understood. This research looks at the production of a solvent-free perovskite solar cells. The solvent free cells degradation mechanism will be studied then compared and contrasted to their solvent made counterparts This research is specifically about optimizing the poly(triaryl amine) [PTAA] layer to obtain the best efficiency in a solvent-free perovskite solar cell.

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.

Optimizing PTAA in a Vapor Deposition Perovskite Solar CellDr. Vikram Dalal, Dr. Ranjith Kottokkaran, Max Noack, Dr. Mahendra Dhaka, Sabrina Stark, Subhash Chander, Behrang Bagheri, Anthony McCutchan

Microelectronics Research Center, Iowa State University

RESEARCH QUESTION/HYPOTHESIS

A look at how varying the thickness of the poly(triaryl

amine) [PTAA] layer effects the efficiency of an organic

hybrid perovskite solar cell.

REFERENCES

1. "Solar Power Energy Information, Solar Power Energy Facts - National Geographic." Solar Energy. National Geographic, n.d. Web. 26 July 2016.

2. "How Much Do Solar Panels Cost to Install on a US Home?" Solar Power Authority. N.p., 19 Apr. 2012. Web. 26 July 2016.

3. "Organic Photovoltaics Research." Department of Energy. ENERGY.GOV Office of Energy Efficiency & Renewable Energy, n.d. Web. 26 July 2016.

4. Li, Xiong, Dongqin Bi, Jean-David Decoppet, and Jingshan Luo. "A Vacuum Flash–assisted Solution Process for High-efficiency Large-area Perovskite Solar Cells." Journals. Sciencemag, 1 July 2016. Web. 26 July 2016.

5. "Energy & Environmental Science." Organometal Halide Perovskite Solar Cells: Degradation and Stability - (RSC Publishing). Publishing Journals Books and Databases, 4 Sept. 2015. Web. 26 July 2016.

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RESULTS & GRAPHICS/CHARTS

BACKGROUND

Energy. It is the one word that defines our world. Energy wakes us, entertains us, keeps us comfortable and allows us to do tremendous work. We as a population have been blessed to find and utilize oil as a source of so much freedom and comfort. This freedom is coming at a price. We are polluting our water and atmosphere with heavy metals and evidence points to the greenhouse effect. We cannot continue on the path we have chosen. Even if petroleum did not contaminate the planet, petroleum is a finite resource. We will eventually run out. Where will we be then? Where will we find our energy? Simply put, the sun produces enough energy in one hour to supply global demand for a whole year1. The problem is being able to harvest it efficiently. Silicon based solar cells are excellent harvesters of the suns rays but they are very cost prohibitive2. Organic solar cells are extremely cheap, but their efficiencies are no where near where silicon based cells are3. Perovskite hybrid solar cells may be an answer to our future needs. They are inexpensive and have hit efficiencies over 20%4. The unfortunate thing about perovskite cells is that they degrade rapidly5. In order for them to become viable, perovskites must be studied to find a way to make them stable. If this can be done, our energy needs could be replaced by an inexpensive solar mean.

METHODS

On a cleaned indium tin oxide (ITO) substrate spin coat and anneal poly(triaryl amine) (PTAA) then co-evaporate lead(II) Iodide(PbI2) with methylammonium Iodide (MAI) and anneal to form a perovskite structured layer, then spin coat and anneal a layer of Pheynl-C61-butyric acid methyl ester (PCBM) and finally evaporate aluminum contacts onto the top layer. (See structure in the “Results” section)

ACKNOWLEDGEMENT

I cannot thank the CBiRC crew enough. I have grown so much as a teacher due to this program, it is my hope that this program lasts forever! To my primary investigator, Dr. Vikram Dalal, I wish to covey my thanks for allowing me to work with you and your fantastic team, I feel honored to have spent my summer with your department. I bow to your wisdom and understanding, may your breakthroughs be countless. To the staff scientist Dr. Max Noack, thank you for all the conversations about so many things, I understand why they say “without Max, nothing can get done.”. To my mentor post docs Dr. Ranjith Kottokkaran and Dr. Mahendra Dhaka, thank you so much for being patient teachers, you have revealed “secrets” that will stay with me for a lifetime. To Behrang Bagheri, thanks for taking the time to explain all the devices and meaning of quantum efficiency. The time spent with you measuring devices was enlightening. Last but not least I wish to thank the most astounding life-partner a person could ever have, Jozette, and our three wonderful children Christopher, Nicholas and Marisa, for letting me be gone during the summer to participate in this program, I love you all very much!

DISCUSSION

Perovskite solar cells, while promising, degrade very quickly. The degradation mechanism is not highly understood. If the degradation mechanism can be identified then perhaps cells could be made to reduce or eliminate the degradation. Dr. Dalal’s group has already produced solvent based perovskite solar cells and are actively studying the degradation mechanism in them, however, they wish to compare those cell stabilities in similar cells that have been made without solvent. These solvent-free cells must be made by vapor deposition. To accurately study the degradation mechanism cells need to be of equivalent efficiency. This study completes a several month research in how to properly control many variables in order to make solvent free perovskite cells that are at or above the fifteen percent efficiency mark. Now that this phase is complete degradation studies can now be started and then be compared to their solvent made equivalents .

PTAA concentration at 2.18 mg/mL

Open current voltage of 0.93 V

Short circuit current density via QE laser of 16.3 mA/cm2

Fill factor via IV curve of 74

Overall efficiency via QE laser of 11.3%

PTAA concentration at 1.45 mg/mL

Open current voltage of 0.93 V

Short circuit current density via QE laser of 19.73 mA/cm2

Fill factor via IV curve of 74

Overall efficiency via QE laser of 14.4%

PTAA concentration at 0.75 mg/mL

Open current voltage of 1.0 V

Short circuit current density via QE laser of 19.83 mA/cm2

Fill factor via IV curve of 77

Overall efficiency via QE laser of 15.1%