Quasi-solid-state monolithic DSSCs with optimized spacer layers and composite electrolytes for better efficiency and stability

In this study, high-performance quasi-solid-state monolithic dye-sensitized solar cells (QS-M-DSSCs) were designed using an optimized spacer layer architecture to enhance electrolyte transport and improve cell performance. Spacer layers, made from a combination of zirconium oxide (ZrO₂) and titanium dioxide (TiO₂), were precisely tuned to reduce mass-transport limitations. A 5.2 μm thick ZrO₂/TiO₂ layer provided good light reflectance and incident photon-to-current conversion efficiency compared to double layers of either material alone. Electrochemical impedance spectroscopy analysis of the m-DSSCs revealed that this architecture (photoelectrode TiO₂ layer/ZrO₂/TiO₂ spacer layer/counter electrode catalyst layer) significantly increased recombination resistance, leading to an improvement in open-circuit voltage. As a result, acetonitrile iodide liquid-DSSCs using N719 dye achieved a high power conversion efficiency (PCE) of 8.45 %, surpassing cells with alternative spacer designs. For fully printable QS-M-DSSCs, printable gel electrolytes (PGEs) composed of polyethylene oxide and polymethyl methacrylate in 3-methoxypropionitrile (MPN) were employed. A 5 wt% PEO/PMMA composition demonstrated fast and efficient penetration of the PGEs through spacer layers. Moreover, incorporation of 4 wt% TiO₂ nanoparticles into PGEs further enhanced their electrochemical properties, achieving a PCE (7.31 %) higher than cells with liquid electrolytes (6.72 %). QS-M-DSSCs demonstrated greater stability than liquid-state DSSCs.