Enhanced stability and ultraviolet photodetection performance in CsPbBr₃ nanoplatelets via FA doping

Quantum-confined CsPbBr₃ nanoplatelets (NPLs) are appealing candidates for ultraviolet (UV)/blue photodetectors due to their strong excitonic binding energy and large absorption coefficient. However, the inherent soft lattice and surface defects of CsPbBr₃ NPLs lead to poor operational stability, limiting their practical applications. Here, we report an A-site alloying strategy that enhances the structural rigidity and defect formation energy of CsPbBr₃ NPLs. The strategy synergistically employs short-chain tetrolic acid (TLA) ligands to passivate uncoordinated Pb²⁺ ions and formamidinium (FA⁺) cations to compensate for Cs⁺ vacancies. This dual repair strategy enhanced both the conductivity and UV irradiation stability of CsPbBr₃-based NPLs. As a result, the self-powered UV photodetectors based on Cs_0.73FA_0.27PbBr₃-TLA NPLs exhibited a responsivity of 89 mA W^-1, a specific detectivity of 3.99 × 10¹² Jones, and an on/off ratio approaching 10⁶ at 0 V bias. Even after 30 days of ambient storage, the device maintained excellent photoresponse and a high specific detectivity of 1.73 × 10¹² Jones. Clear images obtained with a custom-built 2D imaging system corroborate the fast response and excellent stability of the device. These results underscore the efficacy of the combined lattice and surface engineering approach for realizing high-performance, durable perovskite NPL-based UV photodetectors.