Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Comparing the excited-state properties of a mixed-cation–mixed-halide perovskite to methylammonium lead iodide
AU - Brauer, Jan C.
AU - Tsokkou, Demetra
AU - Sanchez, Sandy
AU - Droseros, Nikolaos
AU - Roose, Bart
AU - Mosconi, Edoardo
AU - Hua, Xiao
AU - Stolterfoht, Martin
AU - Neher, Dieter
AU - Steiner, Ullrich
AU - De Angelis, Filippo
AU - Abate, Antonio
AU - Banerji, Natalie
PY - 2020/3/14
Y1 - 2020/3/14
N2 - 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 photogenerated charge carriers upon well 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.
AB - 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 photogenerated charge carriers upon well 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.
U2 - 10.1063/1.5133021
DO - 10.1063/1.5133021
M3 - Journal article
VL - 152
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
SN - 0021-9606
IS - 10
M1 - 104703
ER -