We present a modified architecture of sandwiched heterojunction bifacial perovskite photodetectors where an incident illumination falls directly on the perovskite layer through a window created on charge transport layers. Furthermore, the effects of passivating sandwiched MAPbI3 active layers with MAI solution was investigated. The fabricated photodetectors were electrically, optically and electrochemically characterized as bifacial devices. The champion device displays excellent performance with maximum detectivity and responsivity of 5.96 × 1013 Jones and 1110 A/W respectively. The photodetectors demonstrate good absorbance between 350 nm and 780 nm wavelength range. A maximum external quantum efficiency of 3000% was recorded for the MAI passivated photodetector at 450 nm. After more than 350 days of storage in ambient environment conditions, the champion device shows remarkable stability retaining about 94% of its initial saturated photocurrent, showing remarkable performance metrics retention. For further study, succinct resistance analysis using the EIS measurements were performed. Based on these performance values, this new architecture may instigate future commercial designs of optoelectronic devices to be bifacial and architecturally modified with perovskite window, thereby improving their photon-absorption property, all scaling up towards building highly efficient classes of optoelectronic devices.