Multilayer rapid-drying blade coating for organic solar cells by low boiling point solvents

Abstract

A bulk heterojunction organic solar cell with poly(3-hexylthiophene) (P3HT) as the donor and (6,6)-phenyl-C61-butyric acid methyl ester (PCBM) as the acceptor is deposited using blade coating on a hot plate at 80 degrees C with hot air of 70 degrees C applied from above. In contrast to the 30 min of conventional dichlorobenzene solvent annealing, the rapid-drying blade coating forms a dry film in 1 s. The fabrication throughput is substantially enhanced. The blade-coated film has a smoother surface roughness of 3.5nm compared with 10.5nm for solvent annealing; however, the desired phase separation in the 50nm scale forms despite the rapid drying. A single layer solar cell exhibits power conversion efficiency of 4.1% with blade coating in chlorobenzene, which is the same as solvent annealing device. A multilayer device with carrier blocking layers fabricated entirely of the less toxic toluene also exhibits efficiency of 4.1%. (C) 2014 The Japan Society of Applied Physics