The optimized morphology of polymer:fullerene bulk heterojunction thin film via reducing pressure

The influence of pressure on the morphology of blend film consisted of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C-61-butyric acid methyl ester (PCBM) has been studied in the solvent evaporating process. It is found that the crystalline aggregation of the P3HT component was markedly enhanced in the blend film grown under reduced pressure, compared to that under normal atmospheric pressure. Moreover, the blend film grown under reduced pressure offered greater short-circuit current and power conversion efficiency of a device than that grown under normal atmospheric pressure, mainly ascribing to it that the optimized morphology of the blend film via decreasing pressure improved transport of photo-charges. The pressure effect of PCBM vertical diffusion in the blend film is also discussed.