学术报告: Photovoltaic enhancement accompanied by polar-instability: BiFeO3 vs MAPbI3

报告人: Prof. Junling WANG（School of Materials Science and Engineering, Nanyang Technological University, Singapore）

邀请人：董帅

时间： 10月19日（星期四）下午2点

地点： 田家炳楼南楼205

欢迎各位老师同学参加！

摘要：

Ferroelectric photovoltaic materials have sparked interest recently due to their high photovoltages. However, the low photocurrent and power conversion efficiency limit their applications. The recently discovered hybrid perovskite MAPbI₃, in which a giant photostrictive effect similar to that in ferroelectric oxides has been observed [1], offers a potential avenue to improve the ferroelectric photovoltaic effect. 

It was suggested that the dynamic polar A-site group in MAPbI₃ play a critical role for their ultra-long carrier lifetime. We have investigated the hypothesis using an inorganic perovskite, BiFeO₃. By engineering its A site via La doping, BiFeO₃ displays large photovoltaic enhancement and polar-instability simultaneously. The improvement is attributed to the longer photocarrier lifetime as revealed by optical measurements and supported by theoretical calculations. Such polar-instability-driven band structure tuning may guide future materials design to maintain the momentum of photovoltaic efficiency increase. In addition, we investigate the effects on the carrier lifetime from a subtle direct to indirect band gap transition induced by A-site doping.

Reference:

[1], “Giant Photostriction in Organic-Inorganic Lead Halide Perovskites”, Yang Zhou et al, Nature Communications 7:11193, doi: 10.1038/ncomms11193, (2016).

Biography:

Professor WANG Junling obtained his B.S. degree from Nanjing University in 1999, and Ph.D. degree from University of Maryland, College Park in 2005. After spending 1.5 years at Pennsylvania State University as a postdoc, he joined Nanyang Technological University, Singapore as an Assistant Professor in 2006. He was promoted to Associate Professor with tenure in 2011 and Professor in 2017.

Professor Wang Junling’s research activities focus on perovskites with the chemical formula of ABX₃. These materials possess a wide range of exotic properties ranging from highly insulating to superconducting, from dielectric to ferroelectric and multiferroic. His recent work also includes 2D layered materials that possess ferroelectric and/or magnetic properties. He has published over 120 papers in high impact journals, including Science, Nature Communications, NPG Asia Materials, Advanced Materials, PRB and APL. His work has been cited more than 8000 times.