Phonon-limited Charge Carrier Mobilities in Layered Metal Halide Perovskites

Halide perovskites (HP) arose as formidable building blocks for optoelectronic applications setting record-breaking solar cell performances. The combination of ABX₃ (3D) HP with their layered (2D) counterparts allowed for harvesting the high-efficiency of the 3D materials while maintaining the high stability of layered compounds. [1] However, it is well-known that layered HP exhibits considerably poorer carrier transport than 3D HP, and to date, the mechanisms underlying these lower mobilities remain unknown. [2] In this work, we employ a combination of state-of-the-art many-body approaches and symmetry analysis to investigate the electron-phonon coupling (EPC) origin in layered halide perovskites. [3] By modeling the layered n = 1 and n = 2 cases and the 3D perovskite CsPbBr₃, we demonstrate that the origin of low charge carrier mobilities in layered systems primarily originates from differences in the carrier’s lifetimes. The vibrational modes contributing to carrier scattering are identified via EPC symmetry analysis. Finally, we show that the carrier mobilities are mostly limited by an abrupt increase in the electronic density of states near the band edges. These findings provide a fundamental understanding of the EPC mechanisms intrinsically limiting the charge carrier transport of layered HP, providing pathways for device improvement.

[1] I. Metcalf et al., Chem. Rev. 123, 9565-9652, 2023.

[2] S. G. Motti et al., Adv. Funct. Mater. 33, 2300363, 2023.

[3] H. Lee et al., npj Comp. Mater. 9, 156, 2023.