INVESTIGATIONS OF MATERIALS AND DEVICE STRUCTURES FOR ORGANIC SEMICONDUCTOR SOLAR-CELLS

In our work with the phthalocyanines and perylenes, we have formulated a hierarchy of placement of dyes in p-n heterojunction devices to opt imize the short-circuit current density. Computer modeling of Schottky barrier cells, with parameters fit to experimental results and incorp orating field-dependent carrier generation, were used to optimize the power efficiency. The model predicts an optimum carrier concentration density and suggests different hierarchies for utilization of Forster radiationless energy transfer. Synthesis and purification of materials is also discussed. In terms of purity, most materials used in the lit erature are shown to have been quite below solar grade. A newly devise d purification technique is introduced. A hydration mechanism is shown to exist for chloroaluminum phthalocyanine, previously thought immune to hydration. The latter mechanism had been mistaken before for a sim ple phase transformation and can be induced by various different treat ments with organic nonsolvents for chloroaluminum phthalocyanine. Test ing of p-n and Schottky barrier cells is also discussed. The different capacitance versus voltage (C-V) spectroscopies are compared, and the case for the small-signal method is argued over the triangular voltag e sweep. Several cautions on the interpretation of the C- V curves are noted.