Color-tunable and conductive ITO-based multilayer electrodes for Cu(In,Ga)Se2 thin-film solar cells

To achieve color tunability and electrical conductivity in the front electrodes of thin film solar cells, an indium tin oxide (ITO)-based color filter is designed and fabricated by depositing ITO thin films with various SnO 2 contents via a radio-frequency sputtering process. ITO films containing 5 wt.% and 20 wt.% SnO 2 are selected for multilayer stacking, as they exhibit a significant difference in refractive index while maintaining high electrical conductivity. By alternately stacking these two types of ITO films, a multilayer structure capable of generating diverse visible colors is successfully fabricated. The interfaces between the layers are sharply defined without noticeable interlayer diffusion, enabling precise compositional control that contributed to accurate and consistent optical performance. In addition to its color tunability, the ITO-based multilayer exhibits high optical transmittance and excellent electrical conductivity, making it suitable for application as a transparent front electrode in Cu(In,Ga)Se 2 solar cells. The short-circuit current densities (J sc ), derived from external quantum efficiency (EQE) analysis, ranged from 25.60 to 30.25 mA/cm 2 for the color-filtered devices. These results demonstrate that ITO multilayer color filters provide coloration while preserving effective current generation in thin-film solar cells. • ITO thin films containing 5 wt.% and 20 wt.% SnO 2 were alternately deposited by radio-frequency sputtering to construct a multilayer structure capable of color tuning while preserving high electrical conductivity. • The multilayer ITO color filter produced vivid visible coloration with sharply defined interfaces and negligible interlayer diffusion, ensuring precise compositional control and reproducible optical properties. • When applied as transparent front electrodes in Cu(In,Ga)Se 2 thin-film solar cells, the ITO-based filters exhibited high transmittance and maintained J sc values of 25.60-30.25 mA/cm 2 , confirming efficient photovoltaic performance with minimal optical loss.