ITO-Free Polymer Solar Cells with Ag/WO3 Semi-Transparent Electrodes

We report on the fabrication of the ITO-free polymer solar cells with the structure of silver (Ag)/ tungsten trioxide (WO₃)/regioregular poly-(3-hexylthiophene) (RR-P3HT): [6,6]-phenyl C₆₀ butyric acid methyl ester (PCBM)/ lithium fluoride (LiF)/ aluminum (Al). The Ag/WO₃, which is processed from vacuum deposition method, is used as the anode to instead of the traditional high cost indium tin oxide (ITO) electrodes. The high conductivity metal Ag is used as the anode. Semiconductor materials WO₃, whose valence band of -4.8eV is corresponding to the highest occupied molecular orbital (HOMO) of -5.2eV of P3HT, is used as the hole transport layer (HTL). We have investigated the photocurrent density-voltage (J-V), incident photon-to-electron conversion efficiency (IPCE), and UV-visible spectrum of this device. Therefore we have demonstrated that the ITO-free semi-transparent polymer solar cells can be achieved.