Abstract: A "molecular p-n junction" is formed by an organic compound which has a molecular portion susceptible of electron donation and another molecular portion susceptible of electron acceptance, each of these two portions being within the same compound or molecule and interconnected by a linkage portion. Thus the compound consists of three molecular parts which may in other environments exist as separate molecules. The electron donation molecule and electron acceptance molecule are separated by an intramolecular linkage or chain so that the three form one composite molecule. The donor and acceptor molecules, if the intermolecular linkage is adequate and generally in the preferred range of 15 A to 25 A, or generally between 10 A to 40 A, is susceptible, under the influence of light, of donating an electron to the acceptor. As such, the compound functions as a "molecular p-n junction".