Numerical and experimental investigation of highly flexible, transparent, and conductive WO 3 /Ag/PEI/CuSCN multilayered electrodes

We propose a four-layer WO3/Ag/PEI/CuSCN laminated transparent electrode with a PEI (polyethyleneimine) seed layer. The optical properties of the WO3/Ag/CuSCN electrode were simulated by a transfer matrix theory. Its optimal structure was WO3 (35 nm)/ Ag (9 nm)/CuSCN (47 nm), and the optical transmittance reached 92.7% at a wavelength of 550 nm. The transmittance decreased with the increase of the Ag thickness (> 9 nm). The WO3/Ag/PEI/CuSCN laminated electrode was prepared by a solution method and a vacuum evaporation technique. The quality of an ultra-thin Ag film can be improved via the PEI seed layer in this electrode so that the ultra-thin Ag film has formed a uniform and continuous film at a thickness of 9 nm. The flexible electrode WO3 (35 nm)/Ag (9 nm)/PEI/CuSCN (47 nm) shows a sheet resistance of 10.2 Ω/sq, an optical transmittance of 90% and a surface root mean square roughness of 4.4 nm. The resistance of the electrode remained stable after 1000 times of bending test at a radius of 1 mm, and it has a good mechanical property.