Highly efficient quasi-solid-state dye-sensitized solar cells prepared by printable electrolytes for room light applications

High-efficiency and stable quasi-solid-state dye-sensitized solar cells (QS-DSSCs) are fabricated using printable polymer gel electrolytes for application under room light conditions. The printable electrolytes are prepared based on 3-methoxypropionitrile liquid electrolytes containing iodide/triiodide redox mediator, polyethylene oxide/polyvinylidene fluoride gelator, and titanium dioxide nanofillers. To obtain the optimal performance of the DSSCs, the composition of the printable electrolytes and the thickness of the photoelectrode are regulated. The results show that the polymers composition has little effect on the conversion efficiency of the QS-DSSCs under ambient-light conditions. However, the iodine concentration and the thickness of the titanium dioxide film are important parameters. The experimental results indicate that the printable electrolyte containing 0.01 M iodine, and a titanium dioxide photoelectrode with the thickness of 4 µm main layer and 4 µm scattering layer are the optimal condition to obtain high cell efficiencies. It also shows that the best QS-DSSCs have high recombination resistance and high incident photon to current efficiency values, which contribute, respectively, to the high open circuit voltage and the current density of the corresponding cells. Therefore, the cells can achieve efficiencies of 15.39% and 20.63% under 200 and 600 lx illuminance, respectively. These efficiencies are almost similar to the conversion efficiencies of the corresponding liquid-state DSSC. By applying this printable electrolyte to a sub-module cell, an energy conversion efficiency of 12.23% is achieved under 200 lx illuminance. The study of long-term stability shows that the efficiency of the QS-DSSC can retain 97% of its initial performance after 1000 h testing under 200 lx illuminance, exhibiting high stability of the cells.