Ultrathin Metal Mesh Transparent Electrodes for ITO-Free Organic Photovoltaics

With the advantages of low cost, high transparency and high conductivity, metal mesh electrodes are emerging as promising transparent electrodes in the electronics industry. However, due to the large spacing of the mesh, it is difficult to efficiently collect photogenerated carriers from the active layer, which makes metal mesh electrodes inapplicable to organic photovoltaic (OPV) devices. In this work, we report an ultrathin copper/silver (Cu/Ag) mesh transparent electrode with suitable mesh spacing by ultraviolet lithography technology. The mesh spacing and width can be fine-adjusted to tune the transparency and improve the charge collection efficiency. When the spacing was 5 μm and the width was 1 μm, the mesh electrode exhibited an average visible transmittance (AVT) of 85% with a sheet resistance (R_s) of ∼200 Ω/sq. Adopting this mesh electrode as the bottom transparent electrode, the ITO-free OPV was fabricated with a champion efficiency of 14.2%. Notably, the semitransparent device was also established with an efficiency of 8.3% and an AVT of 30.3% by using the ultrathin Cu/Ag mesh transparent electrode.