Polymer-assisted crystal growth regulation and defect passivation for high-performance flexible solar-blind photodetectors based on copper-based halides

Solar-blind ultraviolet photodetectors have attracted great attention owing to the low background noise and high reliability in operating environments. In this work, we regulated the crystallization of the Cs3Cu2I5 film and passivated defects using a polyvinyl pyrrolidone (PVP) assisted method. As a result, high-quality Cs3Cu2I5 films with compact surfaces, high carrier mobility and fewer defects are obtained. On this basis, the PVP-Cs3Cu2I5 photodetector exhibits a high specific detectivity and responsivity of 1.85 x 1012 Jones and 0.52 A W-1, along with a superior EQE of 45%. Moreover, the flexible PVP-Cs3Cu2I5 device can retain 86.7% of its initial photocurrent after 1000 times bending, benefitting from the enhancement of the mechanical ductility of the Cs3Cu2I5 film by PVP doping. This work provides a promising method for modulating the properties of the Cs3Cu2I5 film for flexible solar-blind photodetectors by suitable polymer additives. A PVP-assisted method regulates the crystal growth of Cs3Cu2I5 films for flexible solar-blind photodetectors.