Carrier mobilities and band alignments of inorganic perovskites of CsBX3†

Exploring carrier mobilities and band alignments of inorganic perovskites is crucial for optimizing their performance in optoelectronic devices, such as solar cells, photodetectors and photodiodes. In this work, electronic structures, carrier mobilities and band alignments of CsBX₃ (B = Pb, Sn; X = Br, I) in the cubic phase (α), tetragonal phase (β) and orthorhombic phase (γ) are investigated by using first-principles calculations. Since the carrier mobilities are severely overestimated based on the acoustic deformation potential (ADP) scattering mechanism, the polar optical phonon (POP) scattering mechanism is thoroughly considered to achieve more accurate carrier mobilities due to the polar ionic crystals of CsBX₃. Remarkably, γ-CsSnI₃ demonstrates high electron and hole mobilities of 1409.94 cm² V⁻¹ s⁻¹ and 870.59 cm² V⁻¹ s⁻¹, respectively. Furthermore, the band alignments of CsBX₃-(001) surfaces with BX₂-terminated and CsX-terminated structures are explored to facilitate the screening of suitable transport layer materials. In particular, CsBX₃ perovskites with BX₂-terminated structures exhibit deeper band edges compared to that with CsX-terminated structures. These findings would provide fundamental insights into the application of CsBX₃ inorganic perovskites in optoelectronic devices.