Novel light-trapping structure having smooth surface for silicon thin-film solar cell

A novel light-trapping structure having a smooth surface likewise character ‘T’ (named as Type-T structure) is proposed for Si thin-film solar cells because the conventional structure based on the surface textures of transparent conductive oxide (TCO) film has crucial issues accomplished by surface roughening. The fundamental concept of Type-T structure, consisting of the roughened surface generating diffusive transmittance (or reflectance) of light as well as the TCO film with the plarnarized surface, is described. The key technique, planarization of roughened surface, has been achieved by the sol-gel prepared ZnO:Al films after the improvement of electrical properties. Finally, applying the Type-T structure to the μc-Si thin-film solar cells, the improvement in the photovoltaic performance, particularly in the short circuit current densities due to the light-trapping effects caused by the Type-T structure, is demonstrated.