Highly Efficient Luminescent Solar Concentrators Based on Capped Carbon Quantum Dots with Unity Quantum Yield

Abstract Luminescent solar concentrators (LSCs) can convert sunlight to clean energy by serving as large‐area collectors of sunlight. Benefiting from their large‐area, semi‐transparency, and lightweight characteristics, LSCs have gained a great of attention. However, their optical efficiency is limited by the low quantum yield (QY) and small Stokes shift of conventional photoluminescent materials. Carbon quantum dots (C‐dots) are promising alternatives, yet achieving both high QY and large Stokes shift has proven challenging. Here, a simple, controllable vacuum heating method is introduced to synthesize highly efficient C‐dots using a citric acid‐urea‐cyanuric acid‐CaCl 2 system. The cyanuric acid‐capped C‐dots exhibit outstanding properties, including a QY of 94.3% in solution and 100% in a polymer matrix, a large Stokes shift of 0.64 eV, and exceptional photostability, making them ideal for LSC applications. Ultrafast transient absorption spectroscopy provides insights into their exciton dynamics. An LSC (25 cm 2 ) based on these C‐dots achieves an optical efficiency of 13.82% ± 0.30%, while its attached photovoltaic cell attains a power conversion efficiency of 4.82% ± 0.10% under natural sunlight (80 mW cm −2 ), marking the highest performance reported for C‐dot‐based LSCs. These results highlight the potential of cyanuric acid‐capped C‐dots for advanced solid‐state lighting and energy conversion technologies.