DSSC- Dye Sensitized Solar Cells
Dye-sensitized solar cells (DSCs) [1] are typically fabricated on transparent conducting glass substrates and comprise a 10 micron-thick, high-surface-area porous layer of TiO2 nanoparticles, a dye monolayer anchored to the TiO2 which absorbs sunlight, an electrolyte which transports charges and a catalytic layer that enables passage of charge from one of the contacts (i.e. the counter-electrode) to the ions in the electrolyte [2]. All these layers can be deposited in solution or via pastes (e.g. screen printing) requiring low cost deposition equipment [3]. Record efficiencies are around 13% over small laboratory cells [4] and 8% over small modules [5-6] under standard test conditions.
A great variety of dyes have bene employed as sensitizers, including organometallic (e.g. N719) and metal-free organic dyes. After the first decade, where organometallic dyes have shown best perfomances, now DSSC record efficiencies approaching 15% have been obtained by using metal-free organic dyes, in some cases in combination with Co-based complexes,[7] which combine higher perfomances with greater variety of properties and much lower synthesis costs.[7-8]
DSCs have demonstrated remarkable power outputs under low level indoor lighting [9-10]. In fact, because of this, and because lifetimes for many indoor applications can be met, industrial outfits such as G24 Power have commercialized DSCs in their flexible form [11] on metal foils (but they can also be developed on plastic films) mainly for these environments.
DSC have attracted a lot interest because they enable to make semi-transparent coloured glass facades desirable for BIPV applications which is potentially a huge market [12-13]. The efficiency, colour and transparency parameters can be tuned depending on applications and they work very well even under indirect light. More R&D is required for attaining a product that is able to consistently guarantee outdoor stability of two decades required for commercialization with a high enough efficiency. Stability can be improved by working on all constituent materials, especially the electrolyte (e.g. quasi solid, or solid mediators) [14-16] although, at the moment, often compromising on the levels of efficiency. Thus, there is room for optimizing the combined efficiency/lifetime parameters for long term outdoor operation.
Published by Thomas Brown, (UTV)
Alessandro Abbotto (UNIMIB), Aldo Di Carlo (UTV)
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