Refractive index dependent optical property of carbon dots integrated luminescent solar concentrators

Colloidal Carbon dots (C-dots) have been used as promising emitters for luminescent solar concentrators (LSCs) due to its high quantum yield, low-cost, non-toxic and simple synthetic method. While it is still very challenging to fabricate high-efficiency LSCs based on C-dots because of strong spectral overlap between the absorption and emission. It is still unclear how the refractive index of the C-dots layer affects the optical properties of LSCs. Here we used liquid junction LSCs as an example to investigate the refractive index effect. A large-area (∼100 cm²) LSC was fabricated by injecting C-dots/polyvinylpyrrolidone solution into a glass mold. The refractive index of the polymer solution can be well controlled in the range of 1.33–1.44 by simply enhancing the polymer concentration. The reabsorption energy loss and the optical efficiency of the LSCs are strongly dependent on the refractive index of the polymer solution. The LSC based on C-dots/polymer exhibits refractive index dependent optical efficiency, as high as ∼0.92% under sunlight illumination, which is 27% enhancement in efficiency over the LSC based on C-dots dispersed in methanol.