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HL: Fachverband Halbleiterphysik

HL 45: Hybrid Perovskite and Photovoltaics I (joint session CPP/HL)

HL 45.2: Vortrag

Mittwoch, 18. März 2020, 09:45–10:00, ZEU 260

Revealing the Impact of Cesium/Rubidium Incorporation on the Photophysics of Multiple-Cation Lead Halide Perovskites — •Yajun Gao, Kai Wang, Mingcong Wang, Jafar Khan, Ahmed Balawi, Stefaan De Wolf, and Frédéric Laquai — King Abdullah University of Science and Technology (KAUST), KAUST Solar Center, Thuwal, Saudi Arabia

The incorporation of cesium (Cs) and rubidium (Rb) ions in multiple-cation mixed lead halide perovskites increases their photovoltaic performance. Here, the reasons for the performance increase are investigated by steady-state and transient spectroscopy techniques. The band edge absorption shows that the Cs/Rb-ion incorporation increases the band gap, while exciton binding energies remain low, in the range of a few milli-electronvolts. Low Urbach energies determined by photothermal deflection spectroscopy suggest optimized microstructures upon Cs/Rb incorporation. The charge carrier recombination dynamics indicate that Cs/Rb-incorporation reduces not only the first-order (trap-assisted) recombination, but also the second-order recombination. Upon photoexcitation, carrier density-induced broadening of the photo-bleaching following the Burstein-Moss model is observed and effective carrier masses are determined to be in the range of a few tenths of the electron rest mass, explaining the excellent charge carrier mobilities of these perovskite films. Sub-picosecond hot carrier cooling is observed, indicating a strong charge-phonon coupling. Our results reveal the impact of cesium/rubidium incorporation on the photophysics of multiple-anion lead halide perovskites.