(a) Fabrication procedure for perovskite thin film using the vapor–solution fabrication method on a patterned ITO/PET substrate. (b) Photograph of a flexible perovskite PD in the bending situation (with interdigital electrodes on the PET substrate). (c) Wavelength-dependent EQE of the flexible PD at different voltages. (d) Photocurrent and EQE of the flexible PD as a function of repetitive bending cycles at 1 V.^[84] (e) Energy diagram of the perovskite PD under a slight reverse bias. (f) Current density–voltage curves of PDs with and without the hole-blocking layer. PD1: without hole-blocking layers; PD2 and PD3: with BCP and PFN as the hole-blocking layers, respectively. (g) Transient photocurrent response at a pulse frequency of 100 kHz with a device area of 0.1 cm² (blue line) and 0.01 cm² (red line). Transient photocurrent response of a silicon diode is shown for comparison.^[38] (h) Transfer characteristics of a perovskite-based phototransistor in the dark (black and red symbols) and under light illumination (blue and magenta symbols). (i) EQE and R of the hybrid perovskite PD at different wavelengths and a V_DS value of −30 V. (j) Temporal photocurrent responses highlighting a rise time of 6.5 μ s and a decay time of 5.0 μ s .^[25]