Journal
NANO LETTERS
Volume 18, Issue 4, Pages 2459-2466Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.8b00035
Keywords
2D layered halide perovskites; quantum coherence; electron-hole recombination; elastic and inelastic electron-phonon scattering; nonadiabatic molecular dynamics; time-dependent density functional theory
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Funding
- National Science Foundation of China [21573022, 21688102, 21590801, 21421003, 5171101561]
- Recruitment Program of Global Youth Experts of China
- Beijing Normal University Startup
- Fundamental Research Funds for the Central Universities [2017EYT09]
- 1000 talents plan
- U.S. National Science Foundation [CHE-1565704]
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Two-dimensional (2D) Ruddlesden-Popper halide perovskites are appealing candidates for optoelectronics and photovoltaics. Nonradiative electron-hole recombination constitutes a major pathway for charge and energy losses in these materials. Surprisingly, experimental recombination is slower in multilayers than a monolayer, even though multilayer systems have smaller energy gaps and higher frequency phonons that should accelerate the recombination. Focusing on (BA)(2)(MA)(n-1)Pbn-1I3n+1 with n = 1 and 3, BA = CH3(CH2)(3)NH3, and MA = CH3NH3, we show that it is the enhancement of elastic electron-phonon scattering that suppresses charge recombination for n = 3, by causing rapid loss of electronic coherence. The scattering is enhanced in the multilayer 2D perovskites because, in contrast to the monolayer, they contain MA cations embedded into the inorganic Pb-I lattice. Although MAs do not contribute directly to electron and hole wave functions, they perturb the Pb-I lattice and create strong electric fields that interact with the charges. The rapid loss of coherence explains long excited state lifetimes that extend into nanoseconds. Both electron-hole recombination and coherence times show excellent agreement with the corresponding lifetime and line width measurements. The simulations rationalize the observed dependence of excited state lifetime in 2D layered halide perovskites on layer thickness and advance our understanding of the atomistic mechanisms underlying charge-phonon dynamics in nanoscale materials.
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