Rashba-Dresselhaus Effect in Inorganic/Organic Lead Iodide Perovskite Interfaces

Despite the imperative importance in solar cell efficiency, the intriguing phenomena at the interface between perovskite solar cell and adjacent carrier transfer layers are hardly uncovered. Here we show that PbI₂/AI-terminated lead iodide perovskite (APbI₃; A = Cs⁺/ methylammonium (MA)) interfaced with the charge transport medium of graphene or TiO₂ exhibits a sizable/robust Rashba-Dresselhaus (RD) effect using density functional theory and ab initio molecular dynamics (AIMD) simulations above the cubic-phase temperature. At the PbI₂-terminated graphene/CsPbI₃(001) interface, ferroelectric distortion toward graphene facilitates an inversion breaking field. At the MAI-terminated TiO₂/MAPbI₃(001) interface, the enrooted alignment of MA⁺ toward TiO₂ by short-strong hydrogen bonding and concomitant PbI₃ distortion preserve the RD interactions even above 330 K. The robust RD effect at the interface even at high temperatures, unlike in bulk, changes the direct-type band to indirect-type to suppress recombination of the electron and hole, thereby letting these accumulated carriers overcome the potential barrier between perovskite and charge transfer materials, which promotes the solar cell efficiency.