Near-infrared light harvesting of upconverting Y2O3:Er3+ nanoparticles and their photovoltaic application

Abstract

Light harvesting plays a significant role in the enhancement on photovoltaic performance. It is closely associated with the photocurrent of solar cells. It is possible to improve light harvesting by material substitution as well as expansion of absorptive edge. Therefore, upconversion characteristics is one of promising solutions for better light harvesting. Upconverting materials emit visible light which is available for photoconversion after they absorb invisible near-infrared (NIR) light. In this study, Er3+ doped Y2O3 (Y2O3:Er3+) nanoparticles were used as upconverting material. Its strong emissions of green and red light corresponding to 2H11/2 and 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions were clearly demonstrated under NIR irradiation of 975 nm wavelength. These emissions were apparently absorbed by dye-sensitized electrode. Based on these results, Y2O3:Er3+ nanoparticles were introduced into dye-sensitized solar cells (DSCs). After incorporating Y2O3:Er3+ nanoparticles, photovoltage was increased due to its high band-gap energy of about 5 eV. On the other hand, the photocurrent was decreased because of the decrease in adsorbed dye amount and electron paths. However, the photoconversion edge was obviously expanded. As a result, DSC performance was enhanced with optimum upconverting particles. It exhibited an efficiency of 8.03%, which was higher than that of a conventional DSC.