Effect of hole transporting layers on the performance of PCPDTBT:PCBM organic solar cells

We study the performance of PCPDTBT : C-71-PCBM organic photovoltaics (OPVs) for three hole transporting layers (HTL); PEDOT : PSS, nickel oxide (NiO) and molybdenum trioxide (MoO3). We show that devices fabricated with nickel oxide HTL demonstrate the highest power conversion efficiency and theoretical data using a transfer matrix model confirms that this is as a result of increased absorption in the active layer as well as a result of improved series resistance and improved matching of energy levels. Device degradation is studied and lifetime is highest for the NiO and MoO3 based devices, proving that OPVs with this material system are less sensitive to the environmental effects of water, oxygen and irradiance.