Enhanced performance of perovskite photodetectors fabricated by two-step spin coating approach

Metal halide perovskite films were prepared using two different deposition techniques, namely one-step spin coating (OSSC) and two-step spin coating (TSSC) and used as the active layer in perovskite photodetectors (PDs). Surface morphology studies revealed that perovskite thin films grown by OSSC exhibited large density of pin holes and non-uniform surface coverage. While, the film produced by TSSC shows full surface coverage with lesser pin holes. By comparing the device performance of the photodetectors based on OSSC and TSSC deposited films, we found that TSSC deposited film based PD demonstrated a significant enhancement in the performance (Responsivity of 1.05 A/W and detectivity of 1.27 x 10(11) Jones @ -1 V) in comparison to the PD based on OSSC deposited films (Responsivity of 0.019 A/W and a detectivity of 1.77 x 10(9) Jones @ -1 V), which can be attributed to the higher absorbance, lesser trap density, narrower trap width, larger carrier mobility and lower leakage current, arising from better surface morphology and crystallinity of TSSC deposited films. Impedance analysis of PD prepared from TSSC film showed a relatively large charge recombination resistance and a long lifetime than PD fabricated from OSSC film, signifying less charge recombination events, which is in consistent with the high performance achieved with the TSSC film based PD.