Realization of Large Open-Circuit Photovoltage in Organic Thin-Film Solar Cells by Controlling Measurement Environment

To obtain large open-circuit photovoltage ( V oc ), we introduced a p -type semiconductor 5,6,11,12-tetraphenylnaphthacene (rubrene), which has a highest occupied molecular orbital (HOMO) level of 5.4 eV. Owing to an adsorption of O 2 and H 2 O into rubrene film, optical absorption peaks were markedly decreased after exposure in air. By controlling the measurement environment to prevent the adsorption of O 2 and H 2 O into rubrene films, we could obtain a high-performance organic thin-film solar cell with a large V oc of 0.91 V.