The interaction between semiconductor materials and electromagnetic fields resonating in microcavities or the light−matter coupling is of both fundamental and practical significance for improving the performance of various photonic technologies. The demonstration of light−matter coupling effects in the emerging perovskite-based optoelectronic devices via optical pumping and electrical readout (e.g., photovoltaics) and vice versa (e.g., lightemitting diodes), however, is still scarce. Here, we demonstrate the microcavity formation in vacuum-deposited methylammonium lead iodide (CH3NH3PbI3, MAPI) p-i-n photovoltaic devices fabricated between two reflecting silver electrodes. We tune the position of the microcavity mode across MAPI's absorption edge and study the effect on the microcavity absorption enhancement. Tuning the microcavity mode toward lower energies enhances the absorption of the lower energy photons and steepens the absorption onset which reduces the effective optical gap (Eg) of the devices. This leads to a reduction in the open circuit voltage deficit.