Towards green, efficient and stable quantum-dot-sensitized solar cells through nature-inspired biopolymer modified electrolyte

Abstract Modifying the polysulfide electrolytes with the polymer additives to suppress the electron-hole recombination process has been proven to be rationally a simple and effective strategy to accomplish efficient and stable quantum dot-sensitized solar cells (QDSSCs). However, compared to the extensively studied organic or inorganic polymer additives, the use of the natural bio-polymer additives in the electrolyte has been less concerned. In this respect, a novel nature-inspired biopolymer, polydopamine (PDA)-based additives are introduced to the polysulfide electrolyte to achieve efficient and stable QDSSCs. Further, the surface and chemical properties of PDA are enriched by functionalization with PEG-NH2 (P-PDA) and subsequent Se doping (Se-PDA). This is the first-ever report using PDA-based additives to regulate the electron-hole recombination dynamics at the TiO2/QDs/electrolyte interface. The QDSSCs fabricated with P-PDA and Se-PDA electrolytes have accomplished higher conversion efficiencies of 7.83% and 8.59%, respectively, compared with that of reference electrolyte (7.62%). Most importantly, PDA-based additives have considerably improved the performance stability of the QDSSCs. The devices that are fabricated with P-PDA and Se-PDA electrolytes displayed 91% and 79% of their original performance after 60 h, respectively; whereas, the liquid electrolyte retained only 11% of its initial performance in the same duration. The long-term stabilities of PDA-based additives are possibly due to the antioxidative property of PDA which may feasibly neutralize the light-induced radicals (R•) in the device. Overall, the novelty of the present work is based on the fabrication of efficient and stable QDSSCs through a cost-efficient and environmentally friendly bio-polymer additive to polysulfide electrolytes.