Integrated energy harvesting and storage device: dye‐sensitized solar cell with Cu(I/II)-based electrolyte and carbon-based aqueous supercapacitor

The energy issue we are facing today, together with greenhouse gas emissions and climate change, is pushing toward the use of renewable technologies; among them solar energy is, to date, the most popular. However, the intermittency of renewable energy sources represents a significant issue to consider, leading to the necessity of accumulating and storing part of the energy produced. Therefore, this work reports the realization of an integrated energy harvesting and storage system made by a dye-sensitized solar cell (DSSC) and a supercapacitor (SC). The integrated system is realized with a three-electrodes stacked configuration in which a shared titanium current collector was coated on both sides by activated carbon and worked both as a counter electrode for the DSSC and as one of the electrodes of the SC. The same material was used for the second electrode of the SC while photo-active electrode of the DSSC was made of a TiO2 layer printed on a FTO (fluorine-doped tin oxide) coated glass substrate. For the DSSC, the combination of XY1 organic dye and [Cu(tmby)2]1+/2+ redox mediator allowed the achievement of an output voltage as high as 0.94 V and a photo-conversion efficiency of 4.23% under simulated solar light. For the SC, Na2SO4 1 M aqueous electrolyte has been employed, reaching a specific capacitance of 104 mF/cm2 and 35.8 F/g. The integrated system showed an overall conversion and storage efficiency of 2.33% under simulated solar and an excellent stability under repeated photo-charge/discharge cycles.