Defect Passivation via Isoxazole Doping in Perovskite Solar Cells

To improve perovskite solar cell (PSC) performance, which is deeply related to perovskite layer quality, researchers have explored numerous strategies. Additive doping into perovskite precursors has been widely used to improve the PSC performance. In this study, we used isoxazole-a Lewis-base small molecule-as an additive for the CH₃NH₃PbI₃ (MAPbI₃) precursor and explored how isoxazole effectively passivates defects in the perovskite structure. We found that isoxazole interacted with undercoordinated Pb²⁺ ions from an X-ray photoelectron spectroscopy survey and verified that isoxazole doping improved the device performance. When the optimized concentration of isoxazole was doped in the MAPbI₃ precursor, the power conversion efficiency increased from 15.6 to 17.5%, with an improved fill factor and short-circuit current density. In addition, an isoxazole-doped device sustained 94% of its initial performance after 8 days under ambient air conditions (10 ± 5 RH %, 25 °C), whereas a device without isoxazole doping only maintained 64% of its initial performance.