Impact of solvent on the downconversion efficiency of the N-GQDs/PMMA layer: Application in CIGS solar cells

Due to lowering the material cost, the thin film-based photovoltaic (PV) technologies are progressively drawing substantial concentration in the PV community. Among them, Cu(In, Ga)Se₂ (CIGS) is considered a potential absorbing material due to its higher absorption and changeable band-gap. But it produced a low value of current at the short wavelength region. Thus, the short circuit current density (J_sc) is greatly reduced, which results in a lower value of the conversion efficiency. Here, N-doped graphene quantum dots (N-GQDs) are used as luminescent photon downshifters (LDS). Furthermore, the N-GQDs are embedded in the poly(methylmethacrylate) (PMMA) to enhance the chemical and mechanical stability of the LDS. However, the PMMA creates the photoluminescence (PL) quenching, which lessens the efficacy of the LDS layer. The LDS composite layer is formed in the various solvents. Furthermore, these LDS composites were evaluated via deployment onto the CIGS solar cells. The best performance is obtained in the chlorobenzene solvent. By insertion of the LDS composite layer, the J_sc was enhanced from 33.58 to 35.32 mA/cm², which resulted in an enhancement in the efficiency from 13.08% to 14.62%. The PV cell parameters analysis revealed that recombination is reduced due to growing the number of photons, which results in the performance enhancement of the CIGS solar cells.