Defects in Perovskites- a Key Differentiator from other Semiconductors

Electronic defects within the band gap of semiconductor materials play critical roles in determining the efficiency and stability of their photovoltaic devices. Eliminating deleterious defects in semiconductors or passivating them during the fabrication process of solar cells has become one of the most fundamental tasks for the solar cell community. This scenario is also prevailing in the metal halide perovskite solar cell community which has witnessed a rapid increase of the power conversion efficiency of perovskite solar cells from 3.8% to over 26% with overwhelming reported progress on defect passivation strategies which also enhance the stability of perovskite solar cells. Any further improvement of the efficiency or stability of perovskite solar cells toward their Shockley-Queisser limitations have to rely on deeper understandings on the nature of defects in perovskite to squeeze out all non-radiative charge recombination paths by eliminating or passivating them.

Here I will present several studies of defects in perovskites, including both deep ones and shallow ones. I will show how we find out the density of defects, distribution, chemical nature, etc, of deep trapping defects.  I will also report our recent discovery of unique properties of shallow defects in perovskites which enable perovskites to be much more defect tolerant.

Jinsong Huang

Department of Applied Physical Science, University of North Carolina, Chapel Hill