Performance improvement of annealing-free P3HT : PCBM-based polymer solar cells via 3-methylthiophene additive

In this work, we studied the effect of 3-methylthiophene (3MT) and 3-hexylthiophene (3HT) additives on the morphology and photovoltaic performance of the polymer solar cells (PSCs) based on P3HT : PCBM (1 : 1 w/w). The P3HT : PCBM blend films prepared from the solutions with 3MT or 3HT additive show enhanced absorption in the 500–650 nm wavelength range and higher hole mobility than that of the film without the additives. X-ray diffraction data indicate a smaller interlayer distance of the conjugated backbones in the 3MT- or 3HT-processed films. Atomic force microscopy images of the 3MT-processed films demonstrate a nanoscaled phase separation and interpenetrating network morphology between the donor and the accept phases. The power conversion efficiency of PSCs based on 3MT-processed blend films without thermal annealing reached 3.72% which is increased by 30% over that of the devices without the additive.