Morphology control of fluorine-doped tin oxide thin films for enhanced light trapping

Current development of fluorine doped tin oxide (FTO) films for the enhancement of light trapping is limited by the tradeoff between roughness and transmittance, since none of them can be improved without sacrificing the other. In this study, we report increases in roughness from 13 to 60 nm and haze from 1.2 to 10.3% for FTO films with a thickness of only 300 nm, by inclusion of different additives into the deposition system. Such significant improvements are achieved whilst maintaining a low resistivity and high transmittance. This results from the development of the desired pyramidal grain morphology associated with the strengthening of (110) preferred orientation and concurrent weakening of (200) and/or (301) preferred orientations. Thus, our study provides a general strategy for developing morphology-controlled FTO films to be compared with current commercial ones with a roughness of 38 nm and a thickness of 800 nm, for improving the light trapping and thus the efficiency of solar cells.