Highly improved efficiency of flexible dye sensitized solar cells (DSSCs) by non-thermal plasma processing of PEI-ITO polymer

This research investigates the impact of non-thermal plasma on the surface properties of an indium tin oxide-coated polyetherimide (PEI-ITO) polymer substrate to enhance the efficiency of dye-sensitized solar cells (DSSCs). Contact angle (CA) measurements indicated that plasma-treated samples quickly became hydrophilic with a dielectric barrier discharge (DBD) treatment time of 60 s, showing a significant increase in surface free energy (SFE). Ageing studies also demonstrated sustained hydrophilicity with CA saturation. The most effective treatment was observed at 60 s, resulting in a CA reduction of over 73% compared to the untreated sample. Investigations into species strength at various peak-peak voltages were conducted using optical emission spectroscopy (OES). Field emission scanning electron microscopy (FE-SEM) analyses were performed to study the structural morphology (surface roughness) of the treated and untreated samples, as well as the TiO2 nanoparticle film. Fourier Transform Infrared Spectroscopy (FTIR) analysis was performed to determine the chemical compositions of the optimal plasma treated and untreated samples. X-ray diffractometer (XRD) analysis was used to determine the crystalline structure of the TiO2 layers. The power conversion efficiency (PCE) of a 10 μm thick TiO2 layer on an untreated substrate was 0.94%. The treated sample with a 10 μm TiO2 layer exhibited the highest PCE of ca. 5.7% on a flexible substrate, representing a novel finding and an efficiency increase of ca. 80% compared to the untreated counterpart. These results suggest that non-thermal plasma modification of PEI-ITO substrates can significantly enhance DSSC performance, including better electrical properties such as improved charge transfer rates, enhanced mobility of charge carriers, and increased conductivity.