Nanoscale microfibrillated cellulose for green polymer electrolytes for DSSCs

As a feasible option for photovoltaic technology to meet the growing energy demand, dye-sensitized solar cells (DSSCs) have attracted much attention due to their low cost, ease of fabrication and good performance. At the same time, polymer electrolytes represent the ultimate in terms of desirable properties of energy conversion devices, as they can offer an all-solid-state construction, a suitable interface with device electrodes, a wide variety of shapes and sizes, light-weight, low costs and safety. In this work, nanoscale microfibrillated cellulose (NMFC) is introduced into a light-cured polymeric matrix, thus resulting in a green, cheap and highly efficient quasi-solid electrolyte for bio-based DSSCs. The effect of NMFC on the photovoltaic parameters and performance of the resulting photoelectrochemical cells is thoroughly investigated, and a noticeable increase in both the photocurrent (due to optical phenomena) and the photovoltage (through a shielding effect on the recombination reactions) is demonstrated. Upon thorough optimization of the amount of NMFC introduced in the polymeric network, sunlight conversion efficiencies as high as 7.03% and 8.25% are achieved at simulated light intensities of 1.0 and 0.4 sun, respectively. Furthermore and outstandingly, NMFC addition also positively affects the long-term stability of the device, which is able to retain > 95% of the initial efficiency after 500 h of extreme aging conditions.