Advancing the stability and efficiency of quantum dot-sensitized solar cells through a novel, green, and water-based thixotropic biopolymer/ordered nanopores silica designed quasi-solid-state gel electrolytes

Abstract

The practical application of liquid electrolyte-constructed quantum-dot sensitized solar cells (QDSSCs) is far from satisfactory due to the short-term performance, poor TiO2 penetration, leakage, and volatilization of liquid electrolytes. In this respect, three of the most critical problems with QDSSCs are addressed in this research: (i) low open-circuit voltage (VOC); (ii) low fill factor (FF), thereby, low efficiency; and, (iii) the device's poor performance stability over time. Herein, a simple approach to fabricate water-based quasi-solid-state gel electrolytes (QSSGE) designed QDSSCs by combining guar gum (GG) biopolymer and ordered nanopores silica (SBA) is reported. For the first time, SBA is being employed as an electrolyte additive to catalyze the reduction of polysulfide electrolyte more efficiently. The resultant SBA/GG gel electrolytes system offers several advantages including (i) passivating the surface trap states between TiO2/QD/electrolyte interfaces; (ii) providing a three-dimensional (3D) porous structure for the free migration of ions; (iii) its surface rich hydroxyl groups establish good contact with the photoanode. The Cu-In-S sensitized devices with SBA/GG gel electrolytes demonstrated superior power conversion efficiencies (PCE) of 9.14% in one full sunlight. This photovoltaic performance is considered to be one of the highest for copper-based QDSSCs. The outstanding PCE with gel electrolyte-constructed QDSSCs are reflected from simultaneous augmentation in VOC and FF that initiated by the synergistic interaction between SBA and GG for controlled interfacial electron-hole recombination dynamics. Moreover, gel electrolyte-constructed QDSSCs outperformed both SBA and liquid electrolyte-constructed QDSSCs in terms of performance stability, lasting up to 168 h instead of 120 or 72 h, respectively. The primary goal of this research is to develop biopolymer-based QSSGEs that are both efficient and stable while also being environmentally beneficial.