Effect of solvent on large-area polymer-fullerene solar cells fabricated by a slot-die coating method

We developed bulk-heterojunction (BHJ) polymer solar cells (PSCs) by slot-die coating a poly(3-hexylthiophene):fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) composites with various solvents, such as chlorobenzene (CB), dichlorobenzene (DCB), or a CB/DCB co-solvent. To understand the effect of solvent on the uniform active layer film coating and charge carrier recombination, we characterized the coated films with UV-visible absorption spectroscopy, and analyzed the measured light intensity dependence of the cells' short-circuit current density (J(sc)) and open-circuit voltage (V-oc). The PSC with the active layer that was made with a CB/DCB co-solvent shows better uniform film quality and power conversion efficiency (PCE) due to its relatively small bimolecular and trap-assisted recombination. Finally, we successfully fabricated a uniform large-area PSC module from P3HT:PCBM with a CB/DCB co-solvent system, which shows a PCE of 1.73% under the condition of air mass 1.5. (C) 2014 Elsevier B.V. All rights reserved.