Environmentally Friendly UV-NIR Dual-Wavelength Excited Upconversion Nitrogen-Doped Graphene Quantum Dots for...

Luminescent materials used in conventional luminescent solar concentrators (LSCs) generally suffer from issues such as heavy metal toxicity, narrow spectral response ranges, significant reabsorption losses, and low near-infrared light utilization efficiency. To address these issues, this study employed a one-step hydrothermal method to synthesize nitrogen-doped graphene quantum dots (N-GQDs) with dual-band excitation capabilities in the ultraviolet and near-infrared regions. They exhibit both large Stokes shift (626 meV), anti-Stokes shift (1143 meV) and high total photoluminescent quantum yield (82.16%). Their luminescent emission peak is located at 440 nm, allowing for stable blue light emission and demonstrating significant upconversion luminescence properties. N-GQDs were encapsulated in polyvinylpyrrolidone to prepare LSCs, which were then coupled with monocrystalline silicon solar cells to construct an LSC-PV system. Under optimal conditions with a quantum dot concentration of 15 mg/mL, the LSC-PV system with dimension of 10 × 10 × 0.3 cm3 achieved a power conversion efficiency of 0.74%, with an efficiency gain of 0.14% attributable to upconversion luminescence. This work demonstrates that N-GQDs with upconversion luminescence properties offer an approach for enhancing the performance of green, high-efficiency building-integrated photovoltaics devices.