Min-Woo Kim1,Stephanie Lee1
New York University1
Min-Woo Kim1,Stephanie Lee1
New York University1
IR photodetectors fabricated using tri-cation (Cs/MA/FA) and dual-anion (Br/I) perovskite as light absorbers exhibit broad light absorption, large charge mobilities, and low-cost fabrication to realize inexpensive but efficient and stable photodetectors. A critical challenge facing their commercialization is their instability under prolonged IR exposure, which can cause parasitic chemical reactions between the perovskite and hole transfer materials (HTMs). Here, we demonstrate 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). These hybrid perovskite photodetectors show ultra-high gains as well as excellent environmental stability. Operating at a low voltage bias of 5 V, the photodetectors exhibit EQE values up to 3008.9 % under 808 nm irradiation, decreasing only to ~ 2769.8 % after 3 months of storage in air. These values are almost ten times higher than those measured for thin film/HTM photodetectors. Such large EQE values for fiber/HTM photodetectors are attributed to the presence of a high density of charge traps on electrospun fiber surfaces that 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 and steady-state photoluminescence measurements and conductive atomic force microscopy mapping revealed that charge transport dynamics are significantly improved in fiber/HTM layers compared to film/HTM layers due to large interfacial areas for exciton dissociation between the two phases in the former case. These results demonstrate the potential of electrospun perovskite hybrid layers to enable the inexpensive fabrication of high-performance IR photodetectors for applications ranging from information technology to imaging.