2. SPATIALLY HETEROGENEOUS CHLORINE INCORPORATION IN ORGANIC-INORGANIC PEROVSKITE SOLAR CELLS
Name: Yanqi Luo
Grad Year: 2020
Perovskite solar cells are hybrid photovoltaic devices and their active layer consists of organic methylammonium halide and inorganic lead halide. The performance of this absorber layer MAPbX3 (X = Cl, I, or Br) can be significantly influenced by its spatial heterogeneities in elemental makeup. Additionally, people have found enhancement of photovoltaic performance by introducing Cl containing precursors during device fabrication process. However, the incorporation of Cl into the final device as well as its electronic impact has remained an open question. In this study, nanoprobe X-ray fluorescence (Nano-XRF) assists to positively identify the presence of chlorine in both films synthesized with Cl-containing precursors and in films synthesized with nominally Cl-free precursors, yielding CH3NH3PbI3-xClx. A statistical analysis is performed on the overall halide ratio maps of Cl:I, to investigate the stoichiometry halide composition ratio within thin films. The films formed from Cl-containing precursors contain roughly an order of magnitude higher amount of chlorine, with average Cl:I values of 0.03. We have found that this average Cl incorporation is independent of whether Cl is present in either the organic or the inorganic precursor for both one- and two-step fabrication processes. More importantly, we also observed a spatial variation in the Cl incorporation within single crystallites and as well as between crystallites within the film from the halide ratio maps. Understanding and controlling this heterogeneous distribution of chlorine in hybrid perovskite layers may offer a path to improve their photovoltaic performance.
Industry Application Area(s)
Energy/Clean technology | Materials