Color tuning in Cu(In,Ga)Se2 thin-film solar cells by controlling optical interference in transparent front layers

Aesthetic factors such as colorization in harmony with the surrounding environment are becoming important in the field of applied photovoltaics. Therefore, there exists a need to realize colors in solar cells, with minimum additional cost and efficiency loss. We tuned the color of Cu(In,Ga)Se-2 thin-film solar cells by controlling the optical interference between the sputtered Zn(O,S) buffer layer and indium tin oxide (ITO) transparent electrode layer, which are intrinsic components of the solar cell device, without any additional process and/or material. The nontoxic Cd-free buffer layer was prepared in consideration of the environmental factor. In order to minimize the degradation of the photovoltaic performance of the solar cell, the experiment was conducted within the thickness (optical path length) of the Zn(O,S) and ITO transparent front layers, which affected the solar cell performance more optically and less electrically. As the antireflection coating thickness increased, the solar cell was calculated to have a wider color range, lower luminosity, and lower J(SC) loss. Relatively even efficiencies were obtained with a wide color range.