The efficiency of solar cells with hybrid perovskites as an active semiconductor has reached 25% efficiency, which is competitive with the industry standard of single-junction silicon-based devices. Hybrid perovskites have the general formula AMX3, where halide anions (X) and the metal (M) form a network of corner-sharing octahedra around the organic A-site cation (A), which sits in the voids between octahedra. Although the first perovskites studied exhibited problems with short stabilities with respect to thermal, light and water-oxygen stability, synthesizing perovskites with a mixture of different halide anions, metals and A-site cations has been shown to improve the stability and efficiency of the semiconductor. The A-site cation affects the electronic properties and structural behavior of the perovskite, however, it is not completely understood how it does so. Our studies show this occurs from organic-inorganic coupling mediated by organic cation dynamics. While optimized devices involve multiple substitutions to create complex alloys, substitutions on single sites provide clear systematic trends. Synthesis of formamidinium lead bromide (FAPbBr3) and cesium substituted-congeners FA(1-x)Cs(x)PbBr3 has enabled investigation of the role that the substitution plays on photovoltaic properties. Photoconductivity and photoluminescence across the solid solution series are correlated with structural changes seen in temperature-dependent X-ray diffraction at Argonne National Laboratory and heat capacity. These structure-dynamics-properties relationships yield a deeper understanding of the origin of high photovoltaic efficiencies of perovskites.

Understanding how dipole dilution in hybrid perovskites affects photovoltaic properties

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.