Abstract
In this work, we fabricated and characterized organic photovoltaic (OPV) devices with hybrid composite anodes containing single-walled carbon nanotube (SWCNT) networks sandwiched between ITO and PEDOT:PSS. The SWCNTs used were initially grown on silicon wafers by a surfactant-free process based on ACCVD (alcohol catalytic chemical vapor deposition), and then transferred to glass substrates with pre-patterned indium-tin-oxide (ITO) electrodes for the fabrication of our OPV devices. We also integrated H <sub>2</sub> SO <sub>4</sub> /HNO <sub>3</sub> -treated and N <sub>2</sub> H <sub>4</sub> -treated SWCNT networks into OPV devices to investigate the effect of chemically-treated SWCNTs on OPV devices' performance. We found that open-circuit voltage (V <sub>oc</sub> ) of our OPV devices was insensitive to SWCNTs' work function shifting caused by the employed chemical treatments, while their short-circuit current (J <sub>sc</sub> ) and power conversion efficiency (PCE) both varied in the order of: reference devices < devices with pristine SWCNT networks < devices with H <sub>2</sub> SO <sub>4</sub> /HNO <sub>3</sub> -treated SWCNT networks < devices with N <sub>2</sub> H <sub>4</sub> -treated SWCNT networks. In particular, we found that integration of N <sub>2</sub> H <sub>4</sub> -treated SWCNTs into the hybrid composite anode could enhance J <sub>sc</sub> by 12% to 20% in P3HT:PCBM OPV devices (with PCE up to 4.02%). The improved performance in devices integrated with N <sub>2</sub> H <sub>4</sub> -treated SWCNTs can be attributed to (i) better crystallinity of the P3HT polymer, and (ii) increased hole-transport efficiency of the hybrid composite anode, both induced by the penetration/digitation of SWCNTs into the P3HT polymer layer. © 2010 The Royal Society of Chemistry.