Towards organic solar cells without the hole transporting layer on the plasmon‐enhanced ITO electrode

Abstract

The avoiding of the hole transport layer (HTL) by an UV/ ozone treatment of the indium tin oxide (ITO) electrode was successfully tested on the P3HT:PC 61 BM and PBDTTT-CF: PC 71 BM organic solar cells with plasmonic gold nanoparticles and gold nanorods spincoated on ITO, respectively. Reference device on bare UV-ozone treated ITO and the one with HTL were also prepared for comparison. It was found that the UV/ozone treatment of the bare ITO and plasmonenhanced ITO electrode allowed an effective alignment of the electrode work function with the polymer in the active layer at the saturated values of 5.5 eV and 5.6 eV, respectively. This result is well explained by the integer charge transfer model. The power conversion efficiency (PCE) of the device on bare UV/ozone treated ITO was comparable to that of the conventional device with HTL. Application of two types of 30 nm gold nanoparticles and 40 nm long gold nanorods on ITO before the subsequent UV/ozone treatment improved the PCE by up to 20% and 10%, respectively. These results suggest feasibility of a simple and cost-effective preparation of OSCs.