High Performance Blue-Targeted Photodetectors Based on Cross-Linked Perovskite/Polymer Composites with Sodium Borate

Si-based materials have been successfully employed in photodiode (PD) sensing applications, but their micrometer-scale thickness requirement and parasitic light absorption pose limitations for color discrimination. Perovskite halide materials have emerged as a promising alternative to conventional Si or III-IV compound PDs. However, the facile degradation of perovskite materials in the presence of humidity and oxygen remains a major challenge for their commercialization. To overcome this issue, we propose a strategy of reducing trap densities as well as improving the crystal quality of perovskite layers based on incorporation of PMMA/sodium borate salt (Borax). Our findings indicate that the PMMA/sodium borate salt additives can serve as both passivator for the uncoordinated Pb²⁺ related to Br^- vacancies and cross-linker between the perovskite polycrystalline grains, which consequently improves the performance and stability of blue-light targeting PDs with high detectivity and responsivity. The blue-targeted PD with the optimized amount of Borax exhibits a superior responsivity of 0.3 A W^-1 (0.85 A W^-1 at 1.4 × 10^-5 W cm^-2 illumination) under 450 nm excitation, an average external quantum efficiency of 77.26% in the 400-500 nm, and over 98% of stability after 50000 on-off cycles, demonstrating a feasible approach for future PD commercialization.