Electrospun Tri‐Cation Perovskite Nanofibers for Infrared Photodetection

Abstract Tri‐cation (Cs + /CH 3 NH 3 + /CH(NH 2 ) 2 + ) and dual‐anion (Br – /I – ) perovskites are promising light absorbers for inexpensive infrared (IR) photodetectors but degrade under prolonged IR exposure. Here, stable IR photodetectors based on electrospun tri‐cation perovskite fibers infiltrated with hole‐transporting π‐conjugated small molecule 2,2′,7,7′‐tetrakis[ N , N ‐di(4‐methoxyphenyl)amino]‐9,9‐spirobifluorene (Spiro‐OMeTAD) are demonstrated. These hybrid perovskite photodetectors operate at a low bias of 5 V and exhibit ultra‐high gains with external quantum efficiencies (EQEs) as high as 3009%, decreasing slightly to ≈2770% after 3 months in air. These EQE values are almost ten times larger than those measured for photodetectors comprising bilayer perovskite/Spiro‐OMeTAD films. A high density of charge traps on electrospun fiber surfaces gives rise to a photomultiplication effect in which photogenerated holes can travel through the active layer multiple times before recombining with trapped electrons. Time‐resolved photoluminescence and conductive atomic force microscopy mapping reveal the improved performance of electrospun fibers to originate from the significantly enhanced interfacial surface area between the perovskite and Spiro‐OMeTAD compared to bilayers. As a solution‐based, scalable and continuous method of depositing perovskite layers, electrospinning thus presents a promising strategy for the inexpensive fabrication of high‐performance IR photodetectors for applications ranging from information technology to imaging.