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Enhanced Open-Circuit Voltage of Wide-Bandgap Perovskite Photovoltaics by Using Alloyed (FA1–xCsx)Pb(I1–xBrx)3 Quantum Dots

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journal contribution
posted on 22.07.2019, 18:35 authored by Mokshin Suri, Abhijit Hazarika, Bryon W. Larson, Qian Zhao, Marta Vallés-Pelarda, Timothy D. Siegler, Michael K. Abney, Andrew J. Ferguson, Brian A. Korgel, Joseph M. Luther
We report a detailed study on APbX3 (A = formamidinium (FA+), Cs+; X = I, Br) perovskite quantum dots (PQDs) with combined A- and X-site alloying that exhibits both a wide bandgap and high open-circuit voltage (Voc) for the application of a potential top cell in tandem junction photovoltaic (PV) devices. The nanocrystal alloying affords control over the optical bandgap and is readily achieved by solution-phase cation and anion exchange between previously synthesized FAPbI3 and CsPbBr3 PQDs. Increasing only the Br content of the PQDs widens the bandgap but results in shorter carrier lifetimes and associated Voc losses in devices. These deleterious effects can be mitigated by replacing Cs+ with FA+, resulting in wide-bandgap PQD absorbers with improved charge-carrier mobility and PVs with higher Voc. Although further device optimization is required, these results demonstrate the potential of FA1–xCsxPb­(I1–xBrx)3 PQDs for wide-bandgap perovskite PVs with high Voc.