Polymer Passivated All Inorganic Micro-Structured CsPbI_xBr_y Perovskite Toward Highly Efficient Photodetectors

Solution-processed inorganic perovskites cause chemical and structural defects unfavorable for photodetector application. Using a binary solvent, defects in CsPbI_xBr_y (CPIB) perovskite are passivated with poly 4-vinylpyridine (PVP) and Poly methyl methacrylate (PMMA) polymers. X-ray photoelectron spectroscopy and FTIR spectra reveal a Lewis base-acid interaction between Pb²⁺ and polymer, confirming the passivation of CPIB perovskite. Scanning electron microscopy analysis shows a dual-surface morphology with microribbons and microcrystals in perovskites. After PMMA treatment, CPIB perovskite exhibits a blue shift in the bandgap (1.8 to 1.95 eV), while the PVP induced a redshift, reducing the bandgap to 1.7 eV. Blue shift in PL analysis indicates modification of grain boundaries. A higher lifetime obtained for CPIB/PVP confirms the restraint of non-radiative recombinations. Photodetectors are fabricated with pristine CPIB, CPIB/PVP, and CPIB/PMMA perovskites. The passivated CPIB/PVP-based photodetector exhibits a quick rise time of ≈23 ms and a decay time of ≈17 ms. It also demonstrates a remarkable photoresponsivity of 23 mA W⁻¹, an internal quantum efficiency of 4.9%, and a detectivity of 15.0 × 10¹⁰ Jones at 10 mW cm⁻² light intensity. This approach shows the potential for environmentally stable polymers to passivate inorganic perovskites for high photodetection performance.