Enhancing the Photovoltaic Performance of Solid-State Dye-Sensitized Solar Cells with Composite Materials and Luminescent Down-Shifting

Abstract

Dye-sensitized solar cells produce saturation of electrons and holes when exposed to high-intensity UV photons. These photon energies do not match the bandgap of the semiconductor materials, which not only degrades the dye and electrolyte but also disrupts the electron kinetics. In this work, graphene oxide (GO) was incorporated into TiO2 to form a composite photoanode structure. The results indicated that a composite photoanode based on GO/TiO2 enhanced the power conversion efficiency of a solid-state dye-sensitized solar cell (ss-DSSC) by 62% compared to that of pure TiO2. This enhancement is attributed to the high conductivity of graphene oxide. Further improvement in device performance was obtained by plasmonic luminescent down-shifting (LDS), where the UV region of the solar spectrum is shifted hundreds of nanometers. The multifunctional LDS coating layer was fabricated with a composite of ZnSe quantum dots and Ag nanoparticles. The experimental results demonstrated the ability of LDS to absorb photons at wavelengths below 400 nm and re-emit them at longer wavelengths (above 400 nm), where the cell has better photovoltaic response. When compared to a bare ss-DSSC, the power conversion efficiency (PCE) is enhanced by 37.62% for cells with a Ag/ZnSe coating layer. Moreover, the LDS-coated device exhibits 16.45% increased photon-to-current conversion efficiency compared to the LDS-free device for wavelengths lower than 500 nm. The 240-h aging tests confirmed that the LDS-coated ss-DSSC retained ∼ 83% of its original PCE value. This potential LDS coating layer not only leads to excellent device stability but also improves the cell performance, which increases the market value of the ss-DSSCs.