SKM 2021 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 8: Poster Session II

HL 8.28: Poster

Dienstag, 28. September 2021, 10:00–13:00, P

Disorder in halide perovskites: anharmonicity and dynamically shortened correlations — •Christian Gehrmann and David A. Egger — Technical University Munich, Germany

Small Urbach energies, important for an effective collection of sunlight in photovoltaic devices, imply a short range correlated disorder potential [1]. Halide perovskites (HaPs), however, are discussed to show a long-range bonding mechanism, anharmonic nuclear dynamics, disorder, and small Urbach energies all at the same time. We show that correlations in the disorder potential for electronic states, calculated using density functional theory (DFT) and DFT-based molecular dynamics simulations, are dynamically shortened in HaPs [2]. This dynamic shortening of the disorder correlation, which we attribute to the motion of A-site and, in particular, X-site ions, results in narrow band-edge energy distributions as we show explicitly. Our findings about correlations in the disorder potential due to nuclear motion is complemented by data showing considerable anharmonicity in the lattice dynamics of CsPbBr₃. With this, we conclude that besides showing complex nuclear dynamics, a mechanism of dynamic shortening of the disorder potential promotes a sharp optical absorption edge in HaPs.

[1] C. W. Greeff & H. R. Glyde, Phys. Rev. B 51, 1778-1783 (1995).

[2] C. Gehrmann & D. A. Egger, Nat. Commun. 10, 3141 (2019).