Indium tin oxide-free polymer solar cells using a PEDOT : PSS/Ag/PEDOT : PSS multilayer as a transparent anode

Cost-efficient indium tin oxide (ITO)-free polymer solar cells (PSCs) based on multilayer poly (3,4-ethylene dioxythiophene) : poly(styrene sulfonate) (PEDOT : PSS)/Ag(15 nm)/PEDOT : PSS (PAP) as the anode were designed and achieved in this work. Compared with the ITO/PEDOT : PSS (IP) and Ag/PEDOT : PSS (AP) layers, the PAP layer showed acceptable optical transparency and electrical conductivity. The average transmittance (350–650 nm) and sheet resistance of PAP were measured to be 50.7% and 2.3 Ω, respectively. In addition, the PAP layer possessed low roughness characterized by atomic force microscopy. In order to investigate the photovoltaic properties of PSCs based on different anodes, devices with the configuration of PAP anode (or IP, AP anode)/poly(3-hexylthiophene) (P3HT) : 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM)/LiF/Al were fabricated. The PAP-based device exhibited reasonable photovoltaic behaviour compared with other devices, and the open-circuit voltage, short-circuit current density, fill factor and power conversion efficiency were calculated to be 0.61 V, 7.01 mA cm−2, 0.69 and 2.99%, respectively. Therefore, PAP was a viable alternative to sputter-grown ITO electrodes, and cost-effective ITO-free PSCs based on a PAP anode could be realized according to this work.