Reflective color filters deposited via ZnS single-target sputtering for colorful solar cell applications

The use of colorful solar cells is necessary for building-integrated photovoltaic (BIPV) applications in urban areas, where aesthetics play an important role. The conventional deposition process of multilayer color filters utilized in solar cells for BIPV applications is expensive because it requires multiple sputter targets. Herein, to address the issue of high cost, a single sputter target was used to produce a color filter consisting of a Zn-based multilayer structure. The oxygen content in the Zn(O,S) films could be controlled by adjusting the amount of oxygen gas supplied during the sputtering process. This allows for control of the optical properties of the films, including the refractive index and extinction coefficient. A color filter with the Zn(O0.92,S0.08)/ZnS structure repeated three times was applied to Cu(In,Ga)Se2 thin-film solar cells; the resulting solar cell demonstrated a wide range of color expressions and less than 10% reduction in optical performance. The proposed technology is expected to significantly reduce the cost of optical filter processes and their applications.