Tuning solar absorption spectra via carbon quantum dots/VAE composite layer and efficiency enhancement for crystalline Si solar module

In this work, fluorescent carbon quantum dots (CQDs) composite transparent film with blue emission was prepared via hydrothermal fabrication, mixing with vinyl acetate‐ethylene (VAE) emulsion, coated and cross‐linked on the glass in sequence. This CQD/VAE film has good sticking ability and compatibility of sealing ethylene‐vinyl acetate (EVA) material and works well as luminescent downshifting (LDS) materials. Based on these features, we did a set of optical characteristics analysis for CQD/VAE film and inserted a CQD/VAE film between glass and EVA encapsulation in a mini metal wrap through (MWT) solar module. This LDS could convert UV part of solar spectra, which are normally blocked by EVA, into the blue range and improve the light absorption by solar cell. Enhancement in the performance of solar modules was proved, especially the improvement of current of short circuit (Isc), external quantum efficiency (EQE) of the UV wavelength and solar module efficiency. This material provides the chance for prompt application, since it simply solves the dispersion problem of LDS material inside encapsulation and keeps the transparency of sealing polymer materials. We design a simple method to make a luminescent, transparent film for solar module lamination process. The enhancements of the Jsc and PCE of Si sample coated with CQD/VAE layers are 1.4% and 2.4%, respectively, at the optimal concentration of 2 wt% of CQD inside VAE film, comparing with twin module without this CQD/VAE film covering. We successfully tune the solar absorption spectra of crystalline Si solar module, and waster UV part is utilized efficiently to contribute the power output.