Theoretic efficiency limit and design criteria of solar photovoltaics with high visual perceptibility

Abstract

Building facades and rooftops provide extensive potential areas for photovoltaic (PV) installation, enabling building-integrated PVs (BIPV) of great interest. PV panels' poor aesthetics, on the other hand, are a key barrier to the wider adoption of BIPV. Although certain PV colorization methods have been developed, the colors obtained are still restricted, particularly those brilliant and low-saturation hues that are desirable for architectural decoration. One concern, therefore, arises whether solar PV can attain high visual perceptibility while also being efficient. To answer this question, here we present a thorough analysis that has quantified the Shockley-Queisser efficiency limits of ideal opaque solar cells with varying lightness. Furthermore, we establish a method for estimating the performance of a real solar cell after colorization. The results suggest that for ideal solar cells with neutral colors that have lightness over 80, the highest efficiency could range between 20.4 % and 25.9 %, with an optimum bandgap between 0.95 and 1.15 eV. The absolute value of over 2 % in efficiency could be further improved if the optimal reflectance is applied to minimize efficiency loss. For the current state-of-the-art solar cell technology, an efficiency limit of 19.8 % is available with the pure white color (RAL 9001). As a result, it could be estimated that silicon solar cells with high visual perceptibility and efficiency limits between 15.4 % and 20.4 % are practically achievable. This study demonstrates its theoretical feasibility, and also inspires the design criteria and evaluation method for practical implementation of solar PVs with high visual perceptibility.