Influence of photoluminescent Si and ZnO QD multilayered films on solar cell efficiency

We report the synthesis and characterization of silicon (Si) and zinc oxide (ZnO) quantum dots (QDs), that exhibit down-shifting photoluminescent characteristics, and their deployment on photovoltaic devices. The ZnO QDs were synthesized in an ethanol-based colloidal solution and dispersed in a matrix of poly-methyl-methacrylate (PMMA), while the Si QDs were synthesized in a water-based colloidal solution and spin cast directly on the window surface of solar cells. The thickness of the photoluminescent coatings for silicon solar cells was theoretically optimized to reduce the reflectivity and verified experimentally for a variety of configurations, including single- layer and double-layer coatings. The analysis also included the effect of the presence of the antireflective layer of silicon nitride on the solar cell surface. The deployment of the aforementioned films as photon down shifting layers on solar cells enabled improvements in the efficiency of the photovoltaic devices from 14.42% to 15.41%. These observations indicate an improvement of ~6.8% in the power conversion efficiency. The identified best practices conducive to increasing the efficiency of photovoltaic devices employing Si and ZnO quantum dots are discussed herein.