Enhancement of poly(3-hexylthiophene)-based solar cell with thermal-evaporated [6,6]-phenyl-C60 butyric acid methyl ester layers

We provide a more compact fabrication process than the prior work using [6,6]-phenyl C61-butyric acid methyl ester (PCBM) buffer layer to enhance the performance of organic solar cells. The device with an extra PCBM layer exhibits an improved power conversion efficiency (PCE) of 20% as compared with the devices with conventional structures. Ultraviolet and x-ray photoemission spectroscopy indicate that thermal annealing treatments result in better mixture structures of PCBM layers with poly(3-hexylthiophene) at the blended surfaces. Therefore, the device with inserted PCBM provides more ideal hetero-structures and vertically graded PCBM distribution to optimize the charge extraction efficiency.