Is there a polaron signature in angle-resolved photoemission of CsPbBr3?

TL;DR

This paper investigates whether large polarons are evidenced in CsPbBr3 by analyzing band dispersion and effective mass, concluding that observed effects can be explained without invoking polaron formation.

Contribution

The study provides a detailed comparison of experimental and theoretical effective masses, challenging previous claims of polaron signatures in CsPbBr3 photoemission data.

Findings

Experimental and theoretical effective masses are nearly identical.

Large-polaron formation is not necessary to explain the data.

Electron-electron correlation accounts for the effective mass enhancement.

Abstract

The formation of large polarons has been proposed as reason for the high defect tolerance, low mobility, low charge carrier trapping and low nonradiative recombination rates of lead halide perovskites. Recently, direct evidence for large-polaron formation has been reported from a 50% effective mass enhancement in angle-resolved photoemission of CsPbBr3 over theory for the orthorhombic structure. We present in-depth band dispersion measurements of CsPbBr3 and GW calculations which lead to almost identical effective masses at the valence band maximum of 0.203+/-0.016 m0 in experiment and 0.226 m0 in orthorhombic theory. We argue that the effective mass can be explained solely on the basis of electron-electron correlation and large-polaron formation cannot be concluded from photoemission data.