High-Efficiency Vivid Color CIGS Solar Cell Employing Nondestructive Structural Coloration

Structural coloration is an effective method for coloring a solar cell with minimum optical loss. For the application of building integrated photovoltaics, it is desirable to integrate structural colors directly onto the solar cell without damaging it with an economical process. Herein, a solution-processed distributed Bragg reflector (sDBR) is introduced to realize efficient and vividly colored CuIn_xGa_(1−x)Se₂ (CIGS) solar cells. The sDBR is directly combined with the CIGS solar cell at room temperature without damaging the photoactive layer. The sDBR is fabricated on CIGS solar cells by spin coating alternate layers of solution-processable TiO₂ nanoparticles bound with acetylacetone and a polymethyl methacrylate solution. The vividly colored CIGS solar cells exhibit high reflectivity and narrow bandwidth at the designated wavelength, resulting in pure red, green, and blue. The reduction in the photocurrent by the coloring is minimized due to the narrow bandwidth characteristics of the sDBR, while a gain in the photocurrent is obtained at wavelengths outside of the range used for coloring due to the antireflection effect of the sDBR. As a result, the power conversion efficiency of R, G, and B sDBR/CIGS solar cells is 97.2%, 99.4% and 102%, respectively, compared to a conventional CIGS solar cell.