Quantitative analysis of the contribution of nanocone gratings to the efficiency of crystalline Si thin-film solar cells

Abstract

Quantitative analysis of the contribution from different physics mechanisms induced by nanocone gratings (NCG) to the efficiency of crystalline Si thin-film solar cells is systematically demonstrated through the performance comparison of such a nanotextured Si solar cell, an equivalent reflection planar Si solar cell, an equivalent volume planar Si solar cell and an actually planar Si solar cell, when their back-interface is a perfect-matched layer or air and their thickness is 1 µm or 10 µm. The results indicate that the contribution of each physics mechanism to the ultimate efficiency and their total contribution are significantly influenced by the thickness of their active layer. When the height of the NCG structure is comparable to the thickness of the active layer, the contribution from each physics mechanism to the efficiency must be considered. In that respect, the contribution from the guided-mode resonance effect is the largest, and even surpasses the contribution of the active layer itself. When the active layer is significantly thicker than the height of the NCG structure, the contribution from antireflection induced by such a nanostructure rises up to the most, and the volume reduction effect can be ignored. In addition, the cavity-resonance effect exhibits a weak contribution and seems to be insensitive to the active layer thickness and interface reflection. Such an investigation provides a methodology to optimize nanostructure-textured thin-film solar cells. Furthermore, the comparison of efficiency between a 1 µm thick NCG-textured solar cell and a 10 µm thick planar solar cell indicates that higher efficiency can be achieved in a thinner Si solar cell by the use of the optimized NCG structure, which just fulfils the expectation of third generation of Si solar cells.