Effect of UV-absorbing small molecule dyes with different alkyl chain densities and branching positions on the photovoltaic performance of semitransparent DSSCs

Abstract

To achieve dye-sensitized solar cells (DSSCs) with high transparency, multi-color capability, and long-term durability for future applications across various fields, this study selected phenylthiophene with UV-absorbing properties as the dye electron donor, cyanoacetic acid as the electron acceptor, and a colorless biphenyl dye (6OBA) as the co-sensitizer. The effects of different alkyl chain lengths, densities, branching positions, and co-sensitization on the photovoltaic (PV) performance of the devices are investigated. In addition, the effect of dye molecules adsorbed on TiO₂ films of different thicknesses on the optical transmittance of the devices was also analyzed. The results show that the developed dyes exhibit UV-selective absorption properties. The power conversion efficiencies (PCEs) of the semi-transparent DSSCs ranged from 0.51% to 0.89% under one sun illumination (100 mW cm⁻²) and from 3.78% to 5.94% under UVA LED illumination (365 nm, 150 μW cm⁻²). The corresponding visible light transmittance varied between 33.47% and 63.71%. At the same time, the DSSCs demonstrated long-term PCE stability after soaking for 1000 hours of full light irradiation.