The interest in monomolecular films as electric conductors arises from the search for innovative materials. The lateral charge transfers in noncovalently bonded films are limited to the distances in the order of a micrometer because they are mechanically unstable and consist of poorly connected domains. Here, we show that a recently developed gas-phase assembling method, which produces robust dense monolayers of NTCD1 (1,4,5.8-naphthalene tetracarboxylic diimide) covalently attached to the surface of silicon, allows one to overcome this scale limitation. These virtually insulating monolayers can be photochemically populated with cation radicals via ejection of electrons into the semiconducting base. The positive charges of cation radicals can migrate as far as several millimeters within microseconds in a random walk fashion thus demonstrating the macroscopic connectivity of the film. Since the charges exist as cation radicals, which are potent oxidants, their migration is coupled to transfer of the free energy of their reduction and is driven by the redox potential gradient. Reduction of cation radicals by an anode converts this free energy into electromotive force. We show how these films can be implemented in solar energy conversion and basic time-resolved distancecontrolled studies of sequences of ultrafast electron transfers.