ABSTRACT
240The concept of an organic p–i–n junction in which i-layer is a co-deposited layer of two different organic semiconductors was proposed and demonstrated. Co-deposited layers have a vast number of heteromolecular (donor–acceptor) contacts acting as efficient photocarrier generation sites. In order to extract the photogenerated carriers from the bulk of the co-deposited films, the nanostructure of the films should be controlled. A crystalline–amorphous nanocomposite with spatially separated pathways for electrons and holes revealed a high efficiency for photocurrent generation. Although perylene pigment/metal-free phthalocyanine in the present study is not the best possible combination, a power conversion efficiency of 1% was obtained. On the other hand, alteration of conduction type from n-type to p-type in a single organic semiconductor of perylene pigment by doping technique was demonstrated. p–n homojunction was successfully fabricated. The concepts and results summarized here offer possible solutions for the realization of practical organic solid-state solar cells that possess a conversion efficiency of over 5%.
