N‐Type Conjugated Polymer as Multi‐Functional Interfacial Layer for High‐Performance and Ultra‐Stable Self‐Powered Photodetectors Based on Perovskite Nanowires

Abstract High‐performance and long‐term stable self‐powered photodetectors (PDs) based on methylammonium lead iodide nanowires (NWs) are demonstrated by incorporating n‐type conjugated polymer poly{2,5‐bis(2‐dodecylhexadecyl)‐3,6‐di(thiophen‐2‐yl)pyrrolo‐[3,4‐c]pyrrole‐1,4(2H,5H)‐dione‐alt‐(E)‐1,2‐bis(3‐cyanothiophen‐2‐yl)ethene} (DPP‐CNTVT) as multi‐functional interfacial layer. Incorporating DPP‐CNTVT with abundant Lewis base functional groups can effectively passivate under‐coordinated Pb 2+ defects, enabling perovskite NWs to exhibit remarkable stability and optoelectronic properties. Meanwhile, high electron mobility, together with the proper energy level of DPP‐CNTVT, makes it ideal for use as an electron transport layer. Particularly, by taking advantage of the low bandgap of DPP‐CNTVT, the utilization of low energy photons can be improved. The resulting PDs exhibit responsivity up to 0.50 A W −1 , specific detectivity approaching 10 14 Jones, and a wide linear dynamic range of nearly 265 dB under zero bias operation, which represent the best results ever reported for self‐powered perovskite PDs. More encouragingly, with the incorporation of an appropriate encapsulation layer, nearly 90% of the initial detectivity of PDs can be secured after 15 300 h of continuous operation in ambient conditions. The application of NWs PDs for solution‐processed reflective‐mode pulse oximetry is also demonstrated. This study provides valuable insights into developing efficient and ultra‐stable self‐powered perovskite PDs through interfacial engineering, which can accelerate the practical applications of this emerging technology.