Aerosol synthesis and luminescent properties of CaAl2O4:Eu2+, Nd3+ down-conversion phosphor particles for enhanced light harvesting of dye-sensitized solar cells

Abstract

The dye molecules generally used in the photoelectrodes of dye-sensitized solar cells (DSSCs) are mostly effective for harvesting visible light. However, the ultraviolet (UV) light component of sunlight is not effectively harvested by these dye molecules. Thus, for inherent improvement of DSSC photovoltaic performance, effective UV light harvesting is necessary. To achieve this, we here attempt to synthesize down-converting phosphor particles, which can convert UV light to visible light. In this work, we fabricate CaAl2O4:Eu2+, Nd3+ phosphor particles using a simple and viable aerosol process in the gas phase; then, we investigate the role of these phosphor particles as a down-converting medium in DSSC photoelectrodes. The presence of Eu2+ and Nd3+ is observed in a CaAl2O4 matrix fabricated at a spray pyrolysis temperature of ∼850 °C with a subsequent H2 reduction temperature of ∼1120 °C. This finding indicates that those conditions are optimized for formation of these components with the strongest emission spectrum peak at ∼440 nm, corresponding to blue light. To examine the effect of the CaAl2O4:Eu2+, Nd3+ phosphor particles on the DSSC photovoltaic performance, various amounts of CaAl2O4:Eu2+, Nd3+ phosphor particles are added to the TiO2 matrixes in the DSSC photoelectrodes. Hence, the short-circuit current density and power conversion efficiency are found to increase with increasing CaAl2O4:Eu2+, Nd3+ phosphor particle content (≤5 wt%) in the TiO2 matrix. This suggests that addition of a critical amount of CaAl2O4:Eu2+, Nd3+ phosphor particles can enhance the DSSC light harvesting efficiency by effectively down-converting UV light from irradiating sunlight into additional visible light.