Dresden 2020 – wissenschaftliches Programm
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CPP 77.1: Vortrag
Mittwoch, 18. März 2020, 15:00–15:15, POT 251
Computational study of the effect of surfaces on the molecular orientation and optical properties of hybrid lead halogenide perovskites — •Gabriele Saleh, Giulia Biffi, and Sergey Artyukhin — Istituto Italiano di Tecnologia, Via Morego 30, Genova 16163 Italy
MAPbX3 perovskites (MA= CH3NH3+, X= Cl,Br,I) are attracting intense interest due to their outstanding performance in optoelectronic devices. The efficiency of MAPbX3 as photovoltaics is governed by the electronic excitation and de-excitation processes. It is widely recognized that MA molecules have an indirect yet strong influence on the band gap and on the optoelectronic properties in general. This effect is particularly intricate since it is depends on the mutual orientations of neighboring molecules (configurations), which is continuously changing at T>100 K . Here we study the energetics of MA configurations near surfaces and the correlation between the dynamical behavior of MA molecules and the optical properties of MAPbX3. Force field molecular dynamics (MD) and electronic structure simulations are performed. We find a linear dependence of the band gap on the octahedral tilt angle of the PbX3 scaffold, which in turn is determined by the orientation of MA molecules. We show how the surface influences the dynamics of MA molecules, and how this affects the surface optical properties. Representative snapshots of MD simulations at different T are extracted and their electronic structure is analyzed in order to explain the measured MAPbBr3 photoluminescence spectra.  O. Selig et al. (2017) J. Am. Chem. Soc., 139, 4068