Work function optimization of vacuum free top-electrode by PEDOT:PSS/PEI interaction for efficient semi-transparent perovskite solar cells

Abstract

Our research group fabricated low temperature based inverted semi-transparent CH3NH3PbI3 perovskite photovoltaics. The work function of PEDOT:PSS (PH1000) electrode was modified using polyethylenimine (PEI) and both layers are transferred on the ITO/PEDOT:PSS/CH3NH3PbI3/PCBM layer using hydrophobic polyurethane acrylate (PUA) polymer stamp. Even if the PH1000 spin coating on the CH3NH3PbI3/PCBM layer shows degradation of perovskite due to the inter-diffusion of PH1000 solvent, drying transfer shows effective layer stacking without degradation. The PEI treatment on the PH1000 contributes to reduce the work function from 5.1eV to 3.97 eV and this modification makes to improve the device performance from 0.07% to 4.02%. The full device average visible transmittance (AVT) exhibits 24.53% and the work function modification shows the decreased charge transporting resistance (R-c), which directly correlate to the enhanced open circuit voltage (V-oc) short circuit current (J(sc)) and fill factor (FF).