Zinc oxide doped single wall carbon nanotubes in hole transport buffer layer

Zinc oxide doped single wall carbon nanotubes (ZnO:CNT) are incorporated in PEDOT:PSS aqueous solution to serve as a hole transport buffer layer in the preparation of thin film organic solar cells (TFOSC). The solar cells were fabricated according to bulkheterojunction design whose photoactive layer is composed of poly (3 hexythiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend. Significant improvement in harvesting photo-generated currents and low series resistances were observed which lead to higher power conversion efficiencies compared to the devices without ZnO:CNT. The optical properties and surface morphologies of ZnO:CNT/PEDOT:PSS hole transport layers are investigated and compared with the changes in the measured parameters of the solar cells. The power conversion efficiency of the devices increased by nearly 116%, 63% and 42% for ZnO:CNT loading at 2.5%, 5% and 10% by weight, respectively, from the devices that uses only PEDOT:PSS as a hole transport layer. Furthermore, a complete recovery of device performance was found by storing the device in warm nitrogen atmosphere.