Display omitted •Simplistic CH3NH3Pb0.99Bi0.01I3/TiO2 bilayer photodetector was fabricated.•The bilayer device demonstrates self-powered photoresponsivity of ~1 × 10−4 AW−1.•Photodetector exhibits nonlinear photoresponse with illumination power densities. In this article, we report the fabrication of self-powered CH3NH3Pb0.99Bi0.01I3 perovskite visible light photodetector by chemical vapour deposition. The crystalline Pb0.99Bi0.01I2 layer grown on TiO2 nanoarrays (NAs) was transformed into trap free CH3NH3Pb0.99Bi0.01I3 functional perovskite layer by exposure of methylamine iodide at various time intervals. The TiO2 NAs improve the morphology and growth of crystalline CH3NH3Pb0.99Bi0.01I3 layers which increases the charge transport and exciton dissociation. Self-powered device resulted in the high photocurrent density of 9.01 × 10−4, 2.65 × 10−3 and 7.06 × 10−3 mA/cm2 under the irradiation of simulated visible solar light at various power densities of 30, 60 and 90 mW/cm2, respectively. The dark current of 10−4 mA/cm2 at 0.3 V clearly evidences ultra-low charge carrier recombination in the bilayer photodetector device. The device accomplishes very good photoresponsivity of ~10−4 AW−1 under self-powered condition.