Characteristics Analysis of Colored Photovoltaic Modules with Bragg Reflectors and Luminescent Down-Shifting Layers

Colored photovoltaic modules (CPMs) have emerged as a highly promising solution to the aesthetic constraints traditionally associated with building-integrated photovoltaics (BIPVs). As urban landscapes increasingly demand more visually appealing renewable energy solutions, CPMs offer an innovative way to integrate photovoltaics seamlessly into building facades without compromising on style. In this study, we explore the theoretical efficiencies of CPMs that incorporate two distinct optical elements: a Bragg reflector (BR) and a luminescent down-shifting (LDS) layer. Our analysis shows that CPMs equipped with LDS layers exhibit superior performance over those utilizing BRs, particularly in achieving vibrant colors with L^* coordinates below 70 in the CIELAB color space. This enhancement is primarily attributed to the LDS layers’ effective utilization of high-energy photons—a region where internal quantum efficiency (IQE) is typically lower.
Conversely, CPMs that integrate BRs are more effective for achieving higher L^* coordinates, especially above 85. The superiority of BRs stems from their ability to provide a narrower reflectance bandwidth, which is essential for producing vibrant and lighter shades. This narrower bandwidth enables more precise color rendering, making BRs particularly effective for colors where accuracy in hue is crucial. Furthermore, our study explores how trap-assisted recombination and energetic disorder affect the operational stability of CPMs. These factors are crucial for enhancing the long-term performance and reliability of photovoltaic systems, as they can significantly influence the efficiency and lifetime of the modules.
Besides, optimal strategies for color generation in CPMs with various photovoltaic module types are also suggested. An in-depth analysis was conducted on the expected changes in the characteristics of LDS-based CPMs, covering technologies such as copper indium gallium selenide (CIGS), dye-sensitized, silicon-based, and next-generation photovoltaics. The results not only define the required IQE characteristics for efficient CPM implementation but also provide comprehensive information on the hues, chromaticity, and brightness levels most advantageous for color generation.
Comprehensively, by tailoring the choice of color generation layer and photovoltaic type, designers can significantly enhance both the efficiency and the aesthetic quality of BIPVs. This tailored approach provides essential guidance for architects and developers looking to integrate CPMs into buildings more effectively, aligning functional energy production with modern architectural aesthetics. These insights pave the way for the next generation of BIPVs, where technology and art converge to power our buildings sustainably and beautifully.