UV-ozone-treated MoO3 as the hole-collecting buffer layer for high-efficiency solution-processed SQ:PC71BM photovoltaic devices

Abstract

The enhanced performance of a squaraine compound, with 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine as the donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the acceptor, in solution-processed organic photovoltaic devices is obtained by using UV-ozone-treated MoO3 as the hole-collecting buffer layer. The optimized thickness of the MoO3 layer is 8 nm, at which the device shows the best power conversion efficiency (PCE) among all devices, resulting from a balance of optical absorption and charge transport. After being treated by UV-ozone for 10 min, the transmittance of the MoO3 film is almost unchanged. Atomic force microscopy results show that the treated surface morphology is improved. A high PCE of 3.99% under AM 1.5 G illumination (100 mW/cm2) is obtained.