Bifacial/Tandem integrated energy harvesting and storage module

Here we propose the fabrication of an energy harvesting and storage device that produces and accumulates energy in a sustainable and green way. The device is composed by a bifacial/tandem dye-sensitized solar module (harvesting) and by a supercapacitor (storage). These two cells share a common electrode, through which the integration becomes possible. The concept of bifacial and tandem properties for DSSCs has been already exploited in literature. The idea is to combine both effects in order to obtain a bifacial and tandem integrated energy harvesting and storage module, to achieve DSSCs characterized by high efficiency values. The goal is to get a new tandem-bifacial configuration, composed by a multilayer of vertically stacked cells. Here two adjacent DSSCs share the counter electrode, leading to the incoming radiation which is not absorbed by the first cell, to be collected by the following one. This causes an increase of the overall efficiency and a reduction of the losses. With this kind of strcture, the need of transparency became crucial together with the requirement to have a counter electrode transparent and conductive on both sides. The improved efficiency is not the only advantage. Also the concept of bifaciality has been enhanced. Using transparent materials, both photoanodes can be front-illuminated, leading to a bifaciality index almost equal to one. Moreover, the fabrication of a series connected module is achieved. It does not improve the cell's operation in terms of efficiency or photo-generated current. The upgrade concerns higher open circuit voltage, allowing the power supply for external devices that usually need voltages greater than 2V to work. Finally, the integration with a supercapacitor is carried on, to allow the energy storage. We choose a SC as the accumulation part for the device because of its advantages. Higher power density, durability, safety and reduced costs, make SC the best choice for this kind of devices. At the same time, another point of interest concerns the choice of the materials used for the fabrication of DSSCs. Their main characteristics, which distinguishes them from other previous generations of PV cells, is based on the fact that they are self-sustainable power source with an immense capacity able to satisfy the energy demands of most indoor electronics. To this aim, DSSCs have been developed as a kind of ambient photovoltaic cells capable of powering autonomous Internet of Things devices. According to this, Michaels et al. have studied and fabricated a DSSC based on materials different from the standard ones, which turned out to be very powerful for indoor applications. A standard DSSC is fabricated with a N719 dye and a iodine based electrolyte. Here, we propose a co-sensitized XY1:L1 dye and a copper based electrolyte, as done by Michaels et al. According to literature, higher efficiencies values have been achieved. These materials allow to reach better performances in terms of indoor illumination, providing the suitable amount of power needed for IoT devices, which is typically low and therefore can be supplied under room light conditions. In conclusion, an innovative and complete harvesting and storage device is here proposed. Particular attentions have been spent on the choice of anodes, counter electrodes, sensitizers and electrolytes in order to exploit an appropriate power supply cell for IoT systems.