The past few years witnessed the explosion of research on photovoltaic cells based on the hybrid lead halide perovskites, in particular CH3NH3PbI3. Within a short period of 5 years, the efficiency of these cells has increased from 3.8% to over 20%. Despite the tremendous progress in device performance, much less is known about the underlying mechanism except that the carrier lifetime and diffusion length are astonishingly long in both thin films and single crystals.
We recently observed a giant photostrictive response, i.e., light-induced dimension change, of more than 1200 ppm in CH3NH3PbI3. This is very similar to what has been observed in conventional ferroelectric oxides. However, the hybrid lead halide perovskites are not ferroelectric despite the large dipole of the CH3NH3 group.
On the other hand, in conventional oxide perovskite BiFeO3 with strong ferroelectricity, we observed that the photovoltaic response could be significantly improved by destabilizing the polarization. Combining these observations, we propose a model to explain the photostriction of CH3NH3PbI3, and suggest a strategy to improve the photovoltaic property of conventonal ferroelectric materials.
1, “Giant Photostriction in Organic-Inorganic Lead Halide Perovskites”, Yang Zhou†, Lu You†, Zhiliang Ku, Hongjin Fan, Shiwei Wang, Daniel Schmidt, Andrivo Rusydi, Lei Chang, Le Wang, Peng Ren, Liufang Chen, Guoliang Yuan, and Junling Wang*, Nature Communications, under review (2015).
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. In 2011, he was promoted to Associate Professor with tenure. He has published over 100 papers in high impact journals, including Science, Nature Communications, NPG Asia Materials, Advanced Materials, PRB and APL. His work has been cited more than 6700 times.