Soft Lattice and Defect Covalency Rationalize Tolerance of β‐CsPbI₃ Perovskite Solar Cells to Native Defects

Abstract

Although all‐inorganic metal halide perovskites (MHPs) have shown tremendous improvement, they are still inferior to the hybrid organic–inorganic MHPs in efficiency. Recently, a conceptually new β‐CsPbI3 perovskite reached 18.4 % efficiency combined with good thermodynamic stability at ambient conditions. We use ab initio non‐adiabatic molecular dynamics to show that native point defects in β‐CsPbI3 are generally benign for nonradiative charge recombination, regardless of whether they introduce shallow or deep trap states. These results indicate that MHPs do not follow the simple models used to explain defect‐mediated charge recombination in the conventional semiconductors. The strong tolerance is due to the softness of the perovskite lattice, which permits separation of electrons and holes upon defect formation, and only allows carriers to couple to the low‐frequency vibrations. Both factors decrease notably the non‐adiabatic coupling and slow down the dissipation of energy to heat.

Chemically Stable Black Phase CsPbI3 Inorganic Perovskites for High‐Efficiency Photovoltaics

“…Prezhdo and co‐workers theoretically demonstrated that β‐CsPbI 3 has the strong defect tolerance originated from the softness of the inorganic lattice and its low‐frequency phonons, which significantly decrease the non‐adiabatic coupling and slow down the dissipation of electronic energy to heat. [ 112 ] This theoretical modeling further confirmed the excellent phase stability of the thermodynamically stable β‐CsPbI 3 . Table 1 compared the performance and stability of current representative CsPbI 3 PSCs prepared by different solution chemistry methods and stabilized by various strategies.…”

Polymerized Hybrid Perovskites with Enhanced Stability, Flexibility, and Lattice Rigidity

“…Weak EPC is expected to reduce non‐radiative recombination rates of excitons in perovskite. [ 25 ] Both temperature‐dependent PLQY and carrier lifetime ( T average ) were measured to examine the recombination dynamics of the polymerized perovskite (Figure S7, Supporting Information). Radiative and non‐radiative recombination rates ( k rad and k non , respectively) are calculated using equations 1/ T average = k rad + k non and PLQY = k rad /( k rad + k non ).…”

Tailored Lattice “Tape” to Confine Tensile Interface for 11.08%‐Efficiency All‐Inorganic CsPbBr3 Perovskite Solar Cell with an Ultrahigh Voltage of 1.702 V

“…As is well known, the soft feature of perovskite film allows for substantial distorted lattices during the phase conversion process under high temperature, which are mainly located at the superficial region and grain boundaries. [ 17 , 18 ] Apart from the popular positive under‐coordinated Pb 2+ ions and negative Pb— X antisites (Pb X 3 − ), the expanded or compressed lattice (in other words, tensile or compressive strain) in this area also determines the carrier transfer and ion migration. [ 19 , 20 ] How to heal the defective nanostructure and to realize the surface solidification undoubtedly maximize the device PCE of PSC.…”