Trapped-Electron-Induced Hole Injection in Perovskite Photodetector with Controllable Gain

Perovskite is an excellent photosensitive material but it exhibits a shortcoming in providing photoconductive gain for layered photodetectors due to lacking of trap states. Here, the perovskite photodetectors are fabricated with controllable photoconductive gain by designing a trapped-electron-induced hole injection structure of [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM):2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ)/Bathocuproine/Au. The deep trap states provided by F4-TCNQ can capture the photogenerated electrons from perovskite, which makes the hole injection barrier thin enough to be tunneled through, allowing the hole injection and forming a gain. Meanwhile, the gain is controllable by adjusting the electron trapping and hole transport capacities of PCBM:F4-TCNQ dual-functional layer, concomitantly realizing the transition of device from photovoltaic to photoconductive. Thus fabricated device achieves a higher external quantum efficiency of 6 x 10(4)% at a lower bias of -1 V, and simultaneously maintains the rectifying behavior in dark, providing the detectivity of about 1 x 10(15) Jones.