Efficient P3HT:SWCNTs hybrids as hole transport layer in P3HT:PCBM organic solar cells

The effects of non-treated and acid treated single wall carbon nanotubes (SWCNTs) were investigated as hybrids with P3HT and P3HT:PCBM blend using UV-Vis absorption spectra, XRD, AFM, SEM, electrical conductivity as well as photovoltaic characteristics under illumination. The absorption spectra have revealed typical absorption peaks around 520 nm which were attributed to the pi-pi* transition of P3HT. XRD patterns, SEM and AFM images have shown a change in the hybrids' structure; the crystallinity peaks were noticeably affected by the addition of SWCNTs, while the morphological investigations have revealed clear features at the organic surface films after treated with SWCNTs. The photovoltaic performance have revealed an increase in the power conversion efficiency (PCE) from 1.52% in the reference P3HT:PCBM-based device to 2.52% in the P3HT:PCBM device with P3HT:SWCNTs as hole transport layer. This enhancement has been ascribed to the increase in the short circuit current density which is associated to an increase in the electrical conductivity. The results have confirmed the ability of SWCNTS to transport holes as it is for electrons; the conjugated polymer twisted around the nanotubes and blocks the way from the electrons and transfer hole.