Aqueous soft matter based photovoltaic devices which mimic leaves and produce electricity

Leaves in sunlightA new type of low-cost, flexible and potentially biocompatible photovoltaic system based on aqueous gel which has the potential for energy generation with minimized environmental pollution has been demonstrated by Orlin D. Velev and colleagues in the USA and South Korea.  The article has received widespread media attention including coverage in the ACS’s Chemical & Engineering News.

Hyung-Jun Koo, Suk Tai Chang, Joseph M. Slocik
Rajesh R. Naik and Orlin D. Velev*
J. Mater. Chem., 2011, Advance Article
DOI: 10.1039/C0JM01820A, Paper

This system consists of two layers of photosensitive ionic dyes infused into a hydrogel which sits between an anode and a cathode.  These dyes capture light and work cooperatively to contribute to the photocurrent generating process both on the surface of the working electrode and in the bulk of the gel.  It was also demonstrated that carbon-coated Cu electrodes could replace the expensive Pt counter electrodes and reduce the production cost without loss of efficiency.

Biomimetic or biocompatible solar cells, inspired by “artificial leaves”, are a novel class of photovoltaics currently being developed which utilise Chlorophyll and photosynthetic reaction centers (Photosystem I and II). This system allows for facile hosting of these naturally derived photosensitive molecules and shows performance comparable with or higher than those of other biomimetic or ionic photovoltaic systems reported recently.

Aqueous soft matter based photovoltaic devicesProfessor Velev explains that  ‘many photoexcitable molecules generate electricity in the right “asymmetric potential” media – used in many organic cells already, but as our medium is water-based it is particularly useful for bioderived molecules’.  However, there are challenges to be solved before these devices can be considered for commercialisation as Professor Velev explains. ‘First, we still have to improve the efficiency of these devices, which is presently very low. Second, we plan to replicate in such devices the ability of the natural leaves to regenerate and replace the organic dye, which will allow us to solve the problems with the long-term stability and performance that are common for all organic photovoltaic devices.  We have clear plans how to address both of these challenges and hope to be able to report the results in future publications’.

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