Quasi-solid-state composite electrolytes with Al₂O₃ and ZnO nanofillers for dye-sensitized solar cells

In the literature, so far, in-situ chemical cross-linking methods have been utilized for the preparation of Al₂O₃ or ZnO-composite polymer gel electrolytes (PGEs). Such PGEs have shown poor performance in quasi-solid-state dye-sensitized solar cells (QS-DSSCs) under one-sun conditions. Moreover, the QS-DSSCs using ZnO-PGEs had higher open-circuit voltages (V_oc) than the cell using Al₂O₃-PGEs; but their conversion efficiencies are much lower. To solve this problem, for the first time, composite printable electrolytes (CPEs) are fabricated by dispersion Al₂O₃ and ZnO nanofillers (NFs) in the quasi-solid-state electrolytes. The electrochemical properties of the CPEs and their effects on the QS-DSSCs performance are systematically studied and compared. The results show that the diffusion coefficients of ions in Al₂O₃–CPEs are much higher than in ZnO–CPEs. However, the introduction of ZnO NFs significantly decreases the charge recombination at the photoelectrode/electrolyte interface than do by the Al₂O₃. Therefore, the QS-DSSCs using Al₂O₃–CPE and ZnO–CPE have, respectively, higher current density and higher V_oc; and the highest efficiencies achieved are 8.73% and 7.59%. These efficiencies are significantly higher than those reported for the QS-DSSC PGEs using the two NFs. The mechanisms of the two NFs are proposed by analysis the iodide ions on the two NFs using X-ray photoelectron spectroscopy and ultraviolet-visible spectroscopy.