Novel cellulose-based composite gel-polymer electrolytes for green, efficient and durable dye-sensitized solar cells

Standard dye-sensitized solar cells (DSSCs) use liquid electrolytes leading to relevant technological drawbacks: poor long-term stability, difficulty in robust and hermetic sealing, electrolyte evaporation/leakage. To improve DSSCs perspectives, recent studies are addressed to the preparation of quasi-solid electrolytes, based on polymer networks able to effectively retain redox mediator/additives. In this work, innovative biocomposite polymer electrolytes for DSSCs, both gelled and/or quasi-solid, based on mixture of polyethylene oxide (PEO) and carboxymethyl cellulose (CMC) or nanoscale microfibrillated cellulose fibres (NFCs) and containing an indigenously made liquid electrolyte containing ionic liquid, supporting salts and the I3-/I- redox couple are prepared. This is the first ever report where the useful aspects of CMC and NFCs as bio-derived DSSC electrolyte components are unravelled and required parameters are thoroughly investigated. Moreover, the performances of lab scale quasi-solid devices are presented, evaluated by means of an innovative combined photovoltaic-chemometric approach. We also present the durability of the devices inherited by different PEO vs. CMC or NFC ratios, as well as the cell response upon various wavelengths and irradiation intensities. The intriguing photovoltaic-chemometric approach allows developing devices with efficiencies in the range of 5 – 7.5 % under 1 sun irradiation (7 – 9 % under 0.4 sun), demonstrating outstanding durability (efficiency retention of 98% after 250 h of extreme aging conditions)