In the paper, the properties of MaPbI3 films made with or without a precipitant have been investigated. The samples had a planar geometry based on ceramic substrates with interdigitated gold electrodes and also based on glass substrates. The samples were irradiated with green light from an LED source, and a special setup was used to measure current–voltage (I–V) characteristics. The polycrystalline films exhibited high sensitivity (an increase in current by about 2 orders upon irradiation). The width of their optical band gap was the same regardless of the use of the precipitant but the maximum trap-filling voltages turned out to be very sensitive to such use. According to optical microscopy, the film microstructure was characterized by a growth of large long dendritic structures, i. e., the nucleation occurred in the solution mass during the films’ making. This growth mechanism may be convenient for the use of MaPbI3 films in photodetectors.