Color Modulation of c-Si Solar Cells without Significant Current-Loss by Means of a Double-Layer Anti-Reflective Coating

Abstract

Standard crystalline silicon solar cells look dark blue because their front surface is coated with a layer of SiNx:H via plasma-enhanced chemical vapor deposition (PECVD) for achieving both passivation and an antireflective coating (ARC). To obtain maximum current under the AM1.5g spectrum, this layer has typically a refractive index n = 2.05 and a thickness d = 76 nm. Achieving other colors by changing n and d reduces the shortcircuit current density Jsc considerably. However, we model and fabricate yellow, red and green solar cells without significant Jsc loss by means of a double-layer ARC (DARC) made by depositing an SiO2 layer on top of the standard SiNx:H layer by PECVD. The experimental outcomes agree well with our simulations. The colored solar cell has a higher reflectivity R() than the standard solar cell in the range of the respective color, but a considerably lower R() at > 820 nm, where the human eye does not perceive color but where both the photon flux and the cell’s internal quantum efficiency are high. Due to this compensation, a Jsc loss is avoided. This makes decorative applications, such as integration into buildings, feasible without trading in a significant power loss.