Methylammonium Chloride reduces the bandgap width and trap densities for efficient perovskite photodetectors

Doping dopants are one of the most effective methods which can improve crystallinity, reduce traps, adjust bandgap width of perovskite films and obtain efficient perovskite photodetectors. Chlorine-based dopants have been reported in many literatures, yet their role still remains a mystery. In our study, a typical solution-processed organic–inorganic hybrid perovskite material CH3NH3PbI3 (MAPbI3) was synthesized as the absorption layer for photodetectors and methylammonium chloride (MACl) was selected as dopant. By tuning the incorporation ratios of MACl in the MAPbI3 precursor solutions, bandgap width and trap densities of the MAPbI3 films can be effectively reduced. The crystallinity and morphology of perovskite films were obviously improved, and the photoelectric properties of photodetectors were further enhanced. Ultimately, the optimal device was obtained when the incorporation ratio of MACl reached 1.0 wt%. External quantum efficiency (EQE) of the optimal device exhibited up to 81%, nearly 30% higher than EQE of the device without incorporation. A lower dark current density (Jd) of 8.4 × 10–8 A cm−2 at − 0.1 V bias was obtained because of low trap densities, moreover, due to the suppressed Jd, the optimal device operating at room temperature showed a specific detectivity (D*) of 2.71 × 1012 Jones and a linear dynamic range (LDR) of 104 dB, higher than the D* of 7.03 × 1011 Jones and the LDR of 91 dB of the device without incorporation, respectively.