Enhancing the performance of flexible dye-sensitized solar cells (FDSSCs) through controlled Ni2+ ion irradiation in the electron transport layer

다국어 초록 (Multilingual Abstract)

Flexible dye-sensitized solar cells (FDSSCs) are an innovative photovoltaic technology for clean and sustainable electricity generation. In the current research, hydrothermally prepared ZnO paste were deposited on indium tin oxide-coated polyethylene terephthalate (ITO–PET) flexible plastic substrates through the spin coating route. To improve the properties of ZnO films, they were irradiated with Ni2+ ions at three different fluencies: 1 × 1013, 1 × 1014, and 1 × 1015 ions/cm2. The structural, morphological, optical, and electrical properties of the pristine and irradiated films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectroscopy, and photoluminescence (PL) analysis. XRD analysis proved that the unirradiated and irradiated ZnO films exhibited hexagonal structure in the wurtzite phase. Specifically, the film irradiated with a fluence of 1 × 1014 ions/cm2 indicating increased crystallinity and larger size of crystallite. SEM observations depicted the nanoflakes, which further elongated in size on exposure to irradiation. SEM analysis also indicated that pores on the surfaces of the ZnO films appeared after irradiation and increased with the ion dose; however, the ZnO film that was irradiated with 1 × 1014 ions/cm2 fluence had the highest pore density. UV–Vis studies revealed a reduction in the bandgap energy (Eg) and an increase in refractive index with the irradiation of Ni2+ ions. A significant decrease in Eg was recorded at 1 × 1014 ions/cm2 fluence. PL spectra indicated reduced peak intensity and recombination rates in the Ni2+-irradiated films, particularly at 1 × 1014 ions/cm2 fluence. Electrochemical impedance spectroscopy (EIS) was employed to investigate the photoelectrochemical behavior of FDSSCs. The results revealed a decrease in charge transport resistance upon Ni2+ ion irradiation, particularly at 1 × 1014 ions/cm2 fluence, effectively reducing charge recombination. The photovoltaic performance of the Ni-irradiated ZnO-FDSSCs exhibited a substantial improvement compared to unirradiated ZnO-FDSSCs, as evidenced by J–V measurements. The highest efficiency achieved was 2.47% at 1 × 1014 ions/cm2 fluence. The main achievement attained in the research work is to improve the efficiency of the ZnO film when irradiated with Ni2+ ions which is due to the more dye adsorption capability of the Ni-irradiated ZnO films, Fermi level rising shift toward conduction band, reduction in bandgap edges, reduction in recombination rate, increase in current density, and reduction in charge transfer resistance that leads to an improvement in photovoltaic properties of FDSSCs.