期刊
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
卷 10, 期 11, 页码 2971-2977出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpclett.9b00876
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资金
- Spanish Ministerio de Ciencia, Innovacion y Universidades [SEV-2015-0496, MAT2015-70850-P]
- FPI fellowship from the Spanish Ministerio - European Social Fund [BES-2016-076913]
- Ph.D. programme in Materials Science from Universitat Autonoma de Barcelona
- EPSRC [EP/G03768X/1, EP/L016354/1]
- European Research Council [ERC CoG648901]
Lead halide perovskites, which are causing a paradigm shift in photovoltaics, exhibit an atypical temperature dependence of the fundamental gap: it decreases in energy with decreasing temperature. Reports ascribe such a behavior to a strong electron-phonon renormalization of the gap, neglecting contributions from thermal expansion. However, high-pressure experiments performed on the archetypal perovskite MAPbI(3) (MA stands for methylammonium) yield a negative pressure coefficient for the gap of the tetragonal room-temperature phase, which speaks against the assumption of negligible thermal expansion effects. Here we show that for MAPbI(3) the temperature-induced gap renormalization due to electron-phonon interaction can only account for about 40% of the total energy shift, thus implying thermal expansion to be more if not as important as electron- phonon coupling. Furthermore, this result possesses general validity, holding also for the tetragonal or cubic phase, stable at ambient conditions, of most halide perovskite counterparts.
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