Improving efficiency of poly(3-hexylthiophene):1-(3-Methoxycarbonyl)- propyl-1-phenyl-(6,6)C61-based organic solar cells by heat-treatment under hydrostatic pressure

Abstract

Hot-pressing, which combined thermal annealing and the in situ application of hydrostatic pressure, was used to improve the efficiency of poly(3- hexylthiophene) (P3HT):1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM)-based organic solar cells. When they were hot-pressed at 0.3MPa and 160 -C for 5 min, their efficiency was approximately 20% higher than that of devices that only underwent heat-treatment. Open-circuit voltage (Voc) remained at around 0.62 V after hot-pressing, but short-circuit current (Jsc) and fill factor (FF) were significantly improved by hotpressing. The hot-pressed devices have higher quantum efficiencies, higher electron mobility, and lower series resistance than those of devices that underwent treatment without pressure. The improvement in the transport of the carriers and the modification of the metal/organic interface properties by hot-pressing contributed to the fill factor, improving the efficiency of the solar cells. The proposed process can be applied to other organic solar cell systems to improve the conversion efficiency. © 2010 The Japan Society of Applied Physics.