Istituto per i Processi Chimico Fisici

The DSSCs represent an alternative and simple, though complex, third generation photovoltaic tool that seeks to help solve global and environmental energy problem. It is recalled that the first generation devices are based on crystalline silicon and used in the common photovoltaic panels, while those of the second generation (“thin film” technologies) are used in the current amorphous silicon panels, CIGS, CdTe. Third generation devices, potentially, could exceed the limitations of predecessors and are based, for example, on organic photovoltaics, on polymeric cells, on those based on quantum dots, on DSSC which are able to provide a cost of production / efficiency of photoconversion more advantageous.[1]

The DSSCs represent an alternative and simple, though complex, third generation photovoltaic tool that seeks to help solve global and environmental energy problems. DSSCs use uncomplicated materials, do not require sophisticated preparation techniques, are close to eco-sustainability and are basically made up of:

• a photoanode, a fundamental component useful for the collection of light energy, formed by a conductive glass (FTO) on which titania nanocrystals are deposited and subsequently sensitized, by simple immersion in a dye solution of synthetic origin (for example Ruthenium compounds ) or natural (anthocyanins, betalains, carotenoids, porphyrins, etc.), this step is referred to as chemiadsorption.[2]
• an electrolytic mediator, ie a solution generally composed of suitable solvents and additives where iodine and its salts are dissolved.
• a cathode, or counterelectrode (CE), which always uses FTO bearing basically Platinum nanoparticles (Pt).[3]
• a sealant useful for coupling the two electrodes and isolating them from the outside.

The photoelectrochemical mechanism that takes place within them is the following: the dye absorbs the photons provided by the light that induce an electronic transition to a higher energy level thus facilitating the transfer to the titania (semiconductor) which, in turn and thanks in the presence of FTO, it transfers the electrons to the EC. If a load (lamp) is interposed between the two electrodes, the flow of electrons performs work (the lamp turns on). At this point the dye has oxidized (it has yielded electrons) and to resume its functionality it needs to be reduced (to reacquire the electrons); this function is carried out by the EC that thanks to the presence of the catalyst (Pt) accelerates the electrons passes to the electrolyte where it meets iodine, which is reduced to iodide and which, in turn, gives the electrons received to the dye making it ready to start another photolithic cycle (an oxidation-reductive equilibrium is always established.

The photoconversion reached in the cell (active area ~ 1cm2) was close to 13% and from this we started to create modules (consisting of several cells connected together in series or parallel) for applications that may require voltages and / or currents most important (5/12 V, 50/500 mA).

The objective of the Group is to follow the fundamental study carried out in the laboratory, the realization of devices that are reliable over time with low production costs.

These “tools” best perform their action in the indoor environment as they respond satisfactorily in conditions of diffused light and could be produced without engaging a fine technology; Essentially an eco-friendly, reliable tool with indoor efficiencies close to 10%  for uses in home automation, sensors, low cost objects, internet of things.

References:
1. Calogero et al. Chem. Soc. Rev.2015, 44 (10), 3244-3294.
2. Calogero et al. Energy & Environ. Sci. 2009, 2 (11), 1162-1172.
3. Calogero et al. Energy & Environ. Sci. 2011 (5), 1838-1844.