Performance enhancement of carbon dot-based luminescent solar concentrators via surface modification and TiO₂-enhanced scattering

Abstract

Carbon dots (CDs) are promising luminescent nanomaterials for a luminescent solar concentrator (LSC) due to facile synthesis, low toxicity, and environmental friendliness; To overcome the limitations of their moderate photoluminescence quantum yields (PLQYs) and photon utilization, in this work, tyramine-modified CDs (Tyr-CDs) were synthesized through a simple one-step surface modification at 250 °C under ambient conditions. After purification by silica gel column chromatography, the average particle size of Tyr-CDs was 32.1 ± 8.1 nm, while the excitation and emission wavelengths remained unchanged compared with unmodified CDs. Nevertheless, Tyr-CDs exhibited stronger UV and visible absorption and higher photoluminescence intensity. The PLQY increased from 56% to 68% through surface modification, which is attributed to the suppression of concentration quenching via steric hindrance that prevents π–π stacking. Embedding Tyr-CDs into ethylene–vinyl acetate (EVA) copolymer produced Tyr-CDs@EVA films, which exhibited improved optical properties compared with CDs@EVA film, which are prepared by embedding unmodified CDs into EVA. When applied to LSC devices, both short-circuit current and power conversion efficiency were significantly enhanced by surface modification with tyramine, which is consistent with the improved optical performance of Tyr-CDs@EVA film. In addition, Tyr-CDs/TiO2@EVA film with a double EVA layer configuration containing individual Tyr-CDs and TiO2 was prepared using 25.4 ± 6.7 nm TiO2 nanoparticles. Compared with Tyr-CDs@EVA film, Tyr-CDs/TiO2@EVA film further improved LSC performance owing to light scattering from TiO2. Moreover, Tyr-CDs+TiO2@EVA film, prepared by dispersing TiO2 and Tyr-CDs together in EVA, achieved the highest power conversion efficiency due to volumetric light scattering.