Improving the efficiency of carbon dots luminescent solar concentrators

Luminescent solar concentrators, or LSCs, are made with transparent glass and designed to absorb sunlight, emit fluorescence, and concentrate the light onto peripheral, smaller photovoltaic cells. Nanoparticles, typically carbon quantum dots and inorganic quantum dots, are used as the luminescent groups in LSCs.

An effective LSC strikes a balance between absorption, which corresponds to energy conversion efficiency, and transmission, which corresponds to transparency. However, carbon dots are weak absorbers compared to inorganic competitors. The result is an LSC with poor efficiency.

Lin et al. investigated the reason for the difference in absorption capacities between the two types of nanoparticles by measuring their absorption spectra in various scenarios. In addition, the team used distributed Bragg reflectors to determine their effects on carbon dot light absorption.

“We found that the light absorption capacity of carbon dots is directly proportional to their size,” said author Yang Song. “In addition, the traditional distributed-feedback Bragg reflector structure was optimized by using a non-periodic, multi-film coating to selectively reflect UV and short-wavelength blue light from sunlight.”

Building on their findings, the authors constructed an improved LSC, increasing the absorption cross-section area of the carbon dots by 2.7 times. Combining this with the innovative reflective coating, they improved the optical efficiency of their device to 9.6%--the highest reported efficiency for carbon dot-based LSCs--while maintaining 71% visible transmittance.

Future work will focus on moving beyond enhanced light absorption efficiency.

“We are working to dynamically adjust the absorption and transmission ratio of LSC devices according to different solar irradiation, balancing the utilization of energy and indoor illumination demands,” said Song.

Source: “Improved light absorption enables highly efficient carbon dots luminescent solar concentrator,” by Jishaui Lin, Lihua Wang, Xiangyong Meng, Weilua Li, Nan Ren, Lin Tao, Junlong Xiao, Qiang Jing, Yang Song, and Haiguang Zhao, Applied Physics Letters (2025). This article can be accessed at https://doi.org/10.1063/5.0245924 .