Solution-processed organic photovoltaic cells with anthracene derivatives

Solution-processed small-molecule bulk heterojunction photovoltaic cells are fabricated by using [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) as electron acceptor and triisopropylsilylethynyl anthracene (TIPSAnt) derivatives substituted with naphthalene (TIPSAntNa) and bithiophene (TIPSAntBT) as electron donors. In contrast to TIPS-pentacene, the TIPSAnt derivatives are not susceptible to Diels-Alder reactions with PCBM when processed in solution, as confirmed by UV/Vis measurements. Photoluminescence quenching measurements show exciton diffusion lengths of 5 and 3 nm for TIPSAntBT and TIPSAntNa, respectively. Blending TIPSAntBT and TIPSAntNa with PCBM (1:1, 1:2, 1:3, and 1:4 weight ratios) produces films that possess adequate hole and electron mobilities. The morphological changes that result from varying the blending ratio range from obvious phase-segregated crystalline domains at a 1:1 ratio to homogeneous, nearly amorphous phases at a 1:4 ratio. Bulk heterojunction solar cells prepared by using a TIPSAntBT: PCBM blend reach power conversion efficiencies as high as 1.4 %.