Charge‐Acoustic Phonon Coupling Determined Carrier Transport Properties in FA _x MA _1−x PbBr ₃ Perovskite Single Crystals

ABSTRACT Mixed‐ion perovskites have attracted wide attention in optoelectronic applications due to their exceptional properties, such as tunable bandgaps and long carrier diffusion lengths. Carrier mobility is a critical factor for determining the performance of optoelectronic devices. However, the substantial variation in reported mobility values has hindered a comprehensive understanding of charge transport in mixed‐ion perovskites. In this work, we conducted time‐domain Brillouin scattering measurements to characterize the elastic constants and deformation potentials of electrons/holes in FA _x MA _1−x PbBr ₃ single crystals. We find that the elastic constants of crystals decrease with the increase of FA content. Applying deformation potential theory to these measured parameters, we determined the intrinsic carrier mobility determined by carrier‐acoustic phonon coupling, and revealed high intrinsic electron and hole mobilities in FA _x MA _1−x PbBr ₃ single crystals. We also find that both electron and hole mobilities, determined by carrier‐acoustic phonon coupling, decrease with the increase of FA content in FA _x MA _1−x PbBr ₃ single crystals. This work advances the comprehension of intrinsic carrier transport properties and offers essential guidance for the rational design of high‐performance perovskite materials.