Double-layered printable electrolytes for highly efficient dye-sensitized solar cells

In this study, novel double-layered electrolyte architecture is first demonstrated for quasi-solid-state dye-sensitized solar cells (DSSCs). The experimental results show that the electrolyte prepared using 9 wt% polymer blends has rheological characteristics suitable for the printing process, and the corresponding DSSC with a double-layered electrolyte architecture reveals an efficiency (7.99%) comparable to that of a common liquid-state cell under 1 sun irradiation. Moreover, when zinc oxide (ZnO) nanoparticles are introduced as the additives in electrolytes, the open-circuit voltage (V_oc) increases, whereas the short-circuit current density (J_sc) decreases. This phenomenon is attributed to the ZnO effects on the two electrodes, i.e., upward shift of the TiO₂ conduction band at the photoelectrode and suppression of interfacial charge transfer at the counter electrode. A solution which takes advantage of the double-layered architecture is proposed herein to overcome the above dilemma. Electrolytes with and without the ZnO additives are printed onto the photoelectrode and counter electrode, respectively. The DSSC prepared by this solution maintains the high V_oc, and furthermore, the J_sc increases, thus achieving an improved efficiency of 8.50%. A similar quasi-solid-state DSSC also outperforms its liquid-state counterpart under indoor fluorescent-light conditions, demonstrating impressive efficiencies beyond 15%.