Roughness improvement of fluorine-doped tin oxide thin films by using different alcohol solvents

Current development of rough fluorine doped tin oxide (FTO) films is limited by the tradeoff of roughness with optical transmittance and electrical resistivity since none of them can be improved without sacrificing the other. In this study, we report a large roughness improvement by using different alcohols for dissolving SnCl4 without losing the conductivity and transmittance, and attribute the improvement to the change from (2 1 1) to (1 1 0) preferred orientation. In the optimal case where ethanol solvent is used, the film has an arithmetic average roughness of 37 nm (root mean square roughness of 45 nm), a transmittance of 85-89%, and a resistivity of 6.3 × 10−4 Ω cm at a thickness of 300 nm. Compared with previous films with a similar roughness but a larger thickness of 800 nm and a lower transmittance of <80%, the present thin film with an excellent combination of high roughness, high transparency, and high conductivity may be used for improving the light trapping and thus the efficiency of solar cells.