Wide Bandgap Organo‐lead Trihalide Perovskites for Solar Cells

Methylammonium lead trihalide perovskite (MAPbX3, where MA is methylammonium, and X is a halide)-based solar cells have been extensively investigated recently, with a demonstrated and certified solar power conversion efficiency (PCE) exceeding 20%. To further boost the PCE beyond the Schockley–Queisser limit, tandem structured solar cells have been investigated based on integrating MAPbX3 and the lower bandgap solar cells. Although the best reported efficiency for this type of tandem cells is not close to the theoretically achievable value, mixed-halide perovskite MAPbBrxI3–x is still one of the most promising candidates as the wide-bandgap light absorber for the tandem application to match the bandgap of silicon, considering its continuously tunable bandgap from 1.6 eV to 2.3 eV with different bromide incorporation ratio. However, the application of the wide-bandgap lead mixed halide perovskite based solar cells has been reported to face several challenges including high intensity of defects, light instability, phase separation, etc. This thesis aims to provide the recent work during my master program involved in the understanding of (1) the characterization of the optoelectronic property of wide-bandgap organolead mixed halide perovskite (MAPbX3), (2) bandgap tunable control of the thin film fabrication process and film post-treatment, (3) device interface and charge transport layers that dramatically influence the efficiency in the MAPbX3 devices, (4) the stability of the MAPbX3 thin films. iii ACKNOWLEDGEMENT First, I would like to express my sincere appreciation to my advisor, Professor Jinsong Huang, who has supported me in my whole master program with his strong expertise and insightful understanding in photovoltaic fields. I thank him for fostering a good and resourceful lab group to conduct research and to receive support from the start of my research career. I have never been more productive in my life than these past two years under his guidance. Through the process of designing the experiments, analyzing the results, writing a peer-reviewed paper, I have learned so much with his patient training. It is his guidance which helped motivate me to explore more and more in this field of study and publish the work we have achieved. Second, I want to express my special thanks to my master degree committee members, Professor Mehrdad Negahban from the Department of Mechanical and Materials Engineering, and Professor Bai Cui from the Department of Mechanical and Materials Engineering for serving in my master supervisory committee. It is my honor to invite you as my master supervisory committee …