Highly efficient and high color rendering index multilayer luminescent solar concentrators based on colloidal carbon quantum dots

Compared to the silicon-based photovoltaics, large-area luminescent solar concentrators (LSCs) can be used as smart PV window for building-integrated photovoltaics (BIPVs). However, because of the low quantum yield of the fluorophores, and reabsorption energy loss, the current obtained large-area LSCs have low optical efficiency. Herein, we demonstrated highly efficient and semitransparent multilayer LSCs based on three types of carbon quantum dots (C -dots). The blue and green C -dots were synthesized using vacuum heating approach and the orange C -dots were synthesized using solvothermal approach. The as-prepared B-, G- and O -C -dots have the QYs of 90 %, 73 % and 72 %, respectively, with large Stokes shift (0.37-0.73 eV). By optimizing the concentration of the C -dots in each layer, the best LSC (100 cm2) with multilayer structure exhibited an external optical efficiency of 9.1 %, and a power conversion efficiency (PCE) of 6.0 %, which are higher than that of most of reported LSCs. The simulations indicate that optimized multilayer LSCs could have a theoretical external optical efficiency over 12 % for 1 m2 devices. Besides high optical efficiency, the multilayer LSCs also have high Color Rendering Index (above 80) and high average visible transmission (above 70 %), which make the as-prepared LSCs suitable for potential commercial BIPVs.