Optimization of the photoelectric performance of large-scale all-flexible dye-sensitized solar cells

Abstract

Highly efficient large scale flexible dye-sensitized solar cells (DSCs) were successfully designed and fabricated. By the introduction of a light scattering layer or pressure, the DSC efficiency was greatly improved. The flexible DSCs with a small surface area (0.4 cm × 0.4 cm) gave a high energy conversion efficiency of 5.50%. The energy conversion efficiencies of large area DSCs (2 cm×3 cm, active area of 2.7 cm2) improved from 1.52% to 1.81% and 2.50%, which is an increase of 20.0% and 66.7% compared with the DSCs prepared without any treatment. The 5 cm×7 cm DSCs (active area of 16.2 cm2) without any optimization showed an energy conversion efficiency of 1.60% under a sunlight intensity of 40 mW·cm-2. The mechanism for the improvement in efficiency was also studied. The results of electrochemical impedance spectroscopy (EIS) demonstrated that the pressure method can significantly reduce the series resistance (Rs) and the charge transfer resistance (Rct) in the TiO2/dye/electrolyte interface. Scanning electron microscopy (SEM) showed that the TiO2 particles were far more closely connected after pressing, which was helpful for electron transport in the TiO2 network as well as for dye adsorption. In addition, the photovoltaic parameters of these flexible DSCs were found to be stable after the 900 h stability tests. The experimental results obtained for these flexible DSCs can be used as a foundation for further basic research and for industrialization technical research. © Editorial office of Acta Physico-Chimica Sinica.