Photo-Switchable Electron-Transporting Layers For Self-Driven Perovskite Photodetectors Towards High Detectivity

Vertical-structure photodetectors usually have the advantages of fast response speed and low driving voltage, but suffer from the high dark current that suppresses the detectivity of the devices. Introducing hole/electron-transporting or blocking layers has thus been widely considered to reduce the dark current, but may simultaneously cause the undesirable loss of photocurrent. Herein, we apply photo-switchable electron-transporting layers into vertical-structure photodetectors, which effectively reduces the dark current without sacrificing photocurrent for achieving the high detectivity. Organic dye molecules, perylene bisimides (PBI-H), are doped into the matrix of zinc oxide (ZnO) to achieve the photo-switchable layer (ZnO:PBI-H), which is less conductive in the dark for the inserted low-conductivity organic molecules but highly conductive under light irradiation due to the photo-induced electron transfer from PBI-H to ZnO. Perovskite is used as the photoactive layer in the photodetectors, and a thin layer of polyethylenimine ethoxylated (PEIE) is inserted between the ZnO:PBI-H layer and the perovskite layer in order to inhibit the decomposition of perovskite caused by ZnO. The optimized photodetector based on a ZnO:PBI-H electron-transporting layer shows the highest detectivity up to 2.5 x 10(13) cm Hz(1/2) W-1 (Jones) at zero bias (light intensity of 126 mu W cm(-2)), which is more than doubled when compared with the device based on ZnO. In addition, the photoresponse stability of the device is also improved by the photo-switchable layer. The primary result sheds new light on the great potential of photo-switchable materials for the development of high-performance photodetectors.