Intense Near-Infrared Light-Emitting NaYF:Nd,Yb-Based Nanophosphors for Luminescent Solar Concentrators.

In this study, we synthesized NaYF-based downshifting nanophosphors (DSNPs), and fabricated DSNP-polydimethylsiloxane (PDMS) composites. Nd ions were doped into the core and shell to increase absorbance at 800 nm. Yb ions were co-doped into the core to achieve intense near-infrared (NIR) luminescence. To further enhance the NIR luminescence, NaYF:Nd,Yb/NaYF:Nd/NaYF core/shell/shell (C/S/S) DSNPs were synthesized. The C/S/S DSNPs showed a 3.0-fold enhanced NIR emission at 978 nm compared with core DSNPs under 800 nm NIR light. The synthesized C/S/S DSNPs showed high thermal stability and photostability against the irradiation with ultraviolet light and NIR light. Moreover, for application as luminescent solar concentrators (LSCs), C/S/S DSNPs were incorporated into the PDMS polymer, and the DSNP-PDMS composite containing 0.25 wt% of C/S/S DSNP was fabricated. The DSNP-PDMS composite showed high transparency (average transmittance = 79.4% for the visible spectral range of 380-750 nm). This result demonstrates the applicability of the DSNP-PDMS composite in transparent photovoltaic modules.