Understanding photogenerated charge transport is critical to further improving the performance of perovskite-based devices. In this study, the low-defect perovskite CH3NH3PbX3 (X = Br or Cl) single crystals, which are an ideal platform for high-quality optoelectronic devices, are fabricated to examine characteristics of photodetectors with electrodes with Au or Ag, and interlayer of TiO2. The transport mechanism of the photogenerated carriers in each device is elucidated by analysis of the current density–voltage curves under dark or a 405 nm of super-bandgap illumination or a 640 nm of sub-bandgap illumination. The photocurrent under the 405 nm illumination is improved under the hole-dominant Au-device of p-type bromide crystals and the electron-dominant Ag-device of n-type chloride crystals. The defect-assisted excitation under 640 nm illumination is associated with generation of the holes with the defects located near the conduction band or the electrons with the valence band in each perovskite materials. With this conception, the responsivity of 0.07 A W−1, specific detectivity over 1011 Jones, and external quantum efficiency around 16% are obtained in the best performing devices. The present results suggest a promising strategy for designing efficient photodetectors using photogenerated and trap-assisted photocarriers that contribute to enhanced photocurrent.
- carrier transport
- single crystals