Comparing the excited-state properties of a mixed-cation–mixed-halide perovskite to methylammonium lead iodide

Brauer, Jan; Tsokkou, Dimitra; Sanchez, Sandy; Droseros, Nikolaos; Roose, Bart; Mosconi, Edoardo; Hua, Xiao; Stolterfoht, Martin; Neher, Dieter; Steiner, Ullrich; De Angelis, Filippo; Abate, Antonio; Banerji, Natalie (2020). Comparing the excited-state properties of a mixed-cation–mixed-halide perovskite to methylammonium lead iodide. The journal of chemical physics, 152(10), p. 104703. American Institute of Physics AIP 10.1063/1.5133021

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Organic–inorganic perovskites are one of the most promising photovoltaic materials for the design of next generation solar cells. The lead-based perovskite prepared with methylammonium and iodide was the first in demonstrating high power conversion efficiency, and it remains one of the most used materials today. However, perovskites prepared by mixing several halides and several cations systematically yield higher efficiencies than “pure” methylammonium lead iodide (MAPbI3) devices. In this work, we unravel the excited-state properties of a mixed-halide (iodide and bromide) and mixed-cation (methylammonium and formamidinium) perovskite. Combining time-resolved photoluminescence, transient absorption, and optical-pump–terahertz-probe experiments with density functional theory calculations, we show that the population of higher-lying excited states in the mixed material increases the lifetime of photo-generated charge carriers upon above- bandgap excitation. We suggest that alloying different halides and different cations reduces the structural symmetry of the perovskite, which partly releases the selection rules to populate the higher-energy states upon light absorption. Our investigation thus shows that mixed halide perovskites should be considered as an electronically different material than MAPbI3, paving the way toward further materials optimization and improved power conversion efficiency of perovskite solar cells.

Item Type:

Journal Article (Original Article)


08 Faculty of Science > Department of Chemistry, Biochemistry and Pharmaceutical Sciences (DCBP)

UniBE Contributor:

Brauer, Jan, Tsokkou, Dimitra, Droseros, Nikolaos, Banerji, Natalie


500 Science > 540 Chemistry




American Institute of Physics AIP


[4] Swiss National Science Foundation




Olivier Nicolas Ludovic Bardagot

Date Deposited:

25 Mar 2020 08:48

Last Modified:

05 Dec 2022 15:37

Publisher DOI:


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Additional Information:

Swiss National Science Foundation: Type: NCCR, Acronym: MUST
Swiss National Science Foundation: Type: Förderungsprofessur/Project Funding, Grant number: PP00P2_150536
University of Bern




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