Chem. J. Chinese Universities ›› 2020, Vol. 41 ›› Issue (3): 439.doi: 10.7503/cjcu20190701

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A-site Cation Effects on Hot Carrier Relaxation in Perovskites by Nonadiabatic Molecular Dynamics Simulations

HE Jinlu,LONG Run,FANG Weihai   

  1. College of Chemistry, Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University, Beijing 100875, China
  • Received:2019-12-23 Online:2020-03-10 Published:2020-02-07
  • Contact: Run LONG,Weihai FANG
  • Supported by:
    † Supported by the National Natural Science Foundation of China(Nos. 21573022);† Supported by the National Natural Science Foundation of China(Nos. 21688102);† Supported by the National Natural Science Foundation of China(Nos. 21590801);† Supported by the National Natural Science Foundation of China(Nos. 21520102005)

Abstract:

In recent years, perovskites have become a research hotspot in the field of solar cells due to their excellent optical and electrical properties. A large number of experiments reported that hot carries relaxation times follow the trend CsPbBr3>MAPbBr3(MA=CH3NH3)>FAPbBr3[FA=HC(NH2)2]. However, the underlying mechanism of the A-site cation(Cs +, MA +, FA +) effects on the relaxation time remains unclear, the hot electrons and holes relaxation of the three perovskiteswere investigated using time-domain density functional theory combined with nonadiabatic molecular dynamics. The obtained time scales agreed well with experiment. This is because A-site cation affects electronic-vibrational coupling with the inorganic Pb—Br framework via electrostatic interaction and hydrogen bond, leading to the strength of nonadiabatic coupling decreasing from FAPbBr3 to MAPbBr3, to CsPbBr3. As a result, the hot carrier relaxation times decreases as the same trend. The study suggests that rational choice of A-site cations provides an excellent strategy to the optimize the performance of perovskite solar cells.

Key words: Perovskite, A-site cation, Hot carrier energy relaxation, Nonadiabatic molecular dynamics, Time-dependent density functional theory

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