Opto-Electronic Properties of Hybrid Perovskites

Abstract

The photovoltaic efficiency utilizing hybrid perovskites as an absorber layer have reached 22% and offers extraordinary potential for clean sustainable energy technologies and also for low-cost optoelectronic devices. In spite of the unprecedented progress, there still exists tremendous variability in the structural and physical properties of these hybrid perovskite based thin-films across the globe. Crystallinity, defect density and impurities are in general determining factors for these physical properties, which are also highly dependent on the materials formation processes. In addition to this, the stability and reliability of perovskite based devices remains open questions and perhaps will determine the fate of this remarkable technology in the longer run. In this talk, I will describe our recently discovered hot-casting approach for thin-film crystal growth as a general strategy for growing highly crystalline, bulk homogenous pin-hole free thin-films of both 3D and layered 2D organometallic perovskites that yield reproducible and stable high efficiency devices and allow access to the intrinsic photo-physical properties. These results are briefly described below. Photovoltaic devices fabricated using 3D hybrid perovskites show hysteresis-free response, with high degree of reproducibility, with an average efficiency of planar devices approaching ~20%. Photo-physical, electrical characterization and theoretical modeling attribute the improved performance to reduced bulk defects and improved charge-carrier mobility in large-grain devices. Furthermore, our most recent efforts on understanding and controlling photo-degradation in these systems demonstrate that the large grain-size perovskite thin-films are not limited by detrimental effects such as ion migration or defect assisted trapping generally reported in perovskite thin-film devices allowing us to probe intrinsic photo-physical processes that lead to the degradation of PCE in perovskite solar cells and control the light-induced degradation in these materials.