Evaluation of pH-tuned ZnO down-shifting photoluminescent quantum dots and their influence on single-crystal silicon solar cells

The present study details the synthesis and characterization of photoluminescent ZnO quantum dots (QDs) and their effect in the performance of in-house-fabricated solar cells. The colloidal ZnO quantum dots were synthetized in an ethanol-based solution, where the growing dynamics was controlled by the pH of the precursor solutions with fixed reaction times. The down-shifting effects of the colloidal quantum dots were characterized by absorption and photoluminescence spectra. Additionally, the crystallographic characterization was performed employing X-ray diffraction (XRD). Planar single-crystal silicon solar cells were fabricated, and their window side was spin-cast with different pH-tuned ZnO quantum dots dispersed in polymethylmethacrylate (PMMA). To evaluate the impact of the aforementioned ZnO QDs films on solar cells, the power conversion efficiency (PCE) values were obtained from the J-V curves generated in a solar simulator and the short-current density (Jsc) was corroborated by external quantum efficiency (EQE) measurements. The mentioned characterization techniques indicated average PCE improvements of 8.67% using pH 10 ZnO QDs + PMMA films and as high as 14.14 % when using pH 12 ZnO QDs + PMMA films. Finally, the reflectance characterization shows a promising anti-reflection effect of the ZnO QDs + PMMA films layers.