Near Infrared Photomuliplication-Mode Perovskite Photodetectors with Various Organic Passive Electron transport Layers

The pace of advancement and increasing stability and perfomances have provided the possibility for perovskite materials to be commercialized in a variety of applications, including solar cells(PVs), light emitting diodes(LEDs) and photodetectors(PDs). As a next-generation semicondutor, advantages of perovskite-based applications are light-weight, solution-processible, tunable bandgap and easy device fabrication.<br/>Two-terminal perovskite photodetectors (PePDs) with p-i-n structure generally have configuration of transparent conducting oxide /hole transport layer/Perovskite/passive-electron transport layer/electrode, wherein the passive electron transport film is mostly organic semiconductors such as C60 and PCBM. The p-i-n structural PePDs are challenging due to several issues. First, photodetectors work in applied negative bias. However, perovskite optoelectronics are quite unstable at strong reverse bias, since the halide migration can occur into organic layers and work as a p-type dopant in the organic layer, leading to accelerate perovskite separation and the device degradation. Secondly, perovskite and the device are significantly affected by following passive-electron transport layers (P-ETLs) and their technical processing methods. To obtain the high quality of perovskite grains and high performance of the device, efficient energy level alignment and interfacial compact between the perovskite layer and organic P-ETL are required.<br/>We investigate NIR perovskite photodetectors by introducing Tin (Sn) with lead (Pb) halide perovskite, which can detect by 1000 nm. We fabricated p-i-n architecture photomultiplication (PM) mode photodetectors devices and compared device performance of different four type organic P-ETLs including C60, PCBM, non-fullerene acceptor (NFA) and Donor polymer:NFA bulk heterojunction (BHJ) blend films to figure out the photomultiplication phenomenon from breakdown of diode at weak reverse voltage. Since the non-fullerene organic material has interesting molecular stacking changes with and without a chloronaphthalene (CN) processing additive, PePDs based on NFA P-ETL with CN also studied in this work. Furthermore, our NIR PM-mode PePDs were fabricated on flexible substrates and applied to photoplethysmogram (PPG) medical monitoring device application. We believe that these comparison of PePDs performance for passive electron transporting organic layers as well as utilizing the photomultiplication present high potential and possibility in the future sensors industrial market.