Self-organized discotic liquid crystals for high-efficiency organic photovoltaics

Self-organization of liquid crystalline and crystalline-conjugated material s has been used to create, directly from solution, thin films with structur es optimized for use in photodiodes. The discotic liquid crystal hexa-peri- hexabenzocoronene was used in combination with a perylene dye to produce th in films with vertically segregated perylene and hexabenzocoronene, with la rge interfacial surface area. When incorporated into diode structures, thes e films show photovoltaic response with external quantum efficiencies of mo re than 34 percent near 490 nanometers. These efficiencies result from effi cient photoinduced charge transfer between the hexabenzocoronene and peryle ne, as well as from effective transport of charges through vertically segre gated perylene and hexabenzocoronene pi systems. This development demonstra tes that complex structures can be engineered from novel materials by means of simple solution-processing steps and may enable inexpensive, high-perfo rmance, thin-film photovoltaic technology.