PTFE/MoO3 Anode Bilayer Buffer Layers for Improved Performance in PCDTBT:PC71BM Blend Organic Solar Cells

This paper discusses the effects of an anode bilayer buffer layer on poly[N-9"-hepta-decanyl-2,7-carbazolealt-5,5-(4',7'-di-2-thienyl-2',1',3'-ben-zothiadiazole)]: [6,6]-phenyl-C71-butyric acid methyl ester (PCDTBT:PC71BM) based organic solar cells (OSCs) by thermally evaporating poly(tetrafluoroethylene) (PTFE) and molybdenum trioxide (MoO3) successively between indium tin oxide (ITO) and the active layer. The PTFE/MoO3 bilayer forms an interfacial dipole that increases the surface work function of the ITO anode, which contributes to the extraction of holes and the suppression of carrier recombination at the interface. The replacement of the conventional hygroscopic and acidic poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with PTFE/MoO3 is advantageous for efficient charge transport and reduction of the fabrication costs. Significant improvement in terms of the fill factor and power conversion efficiency (PCE) is obtained compared to the reference devices. The improvement of device performance in PTFE/MoO3 bilayer structure results from its combined effects of tuning work function ability and electron-blocking capacity of PTFE and excellent hole-extracting capability of MoO3.