Shrimp Shells for Cheaper Solar Cells
Scientists have developed an exciting method to make cheaper solar cells, using biological compounds found in shrimp shells. While currently in its early stages, this method could revolutionise photovoltaic technology by reducing the cost of materials used to convert light energy into electricity.
Solar cells are used all over the world to provide clean electricity, and are important power-providers in remote locations, research stations and satellites. However, widespread use of solar power is restricted by the cost of the technology, which remains high due to the expensive materials used.
The majority of solar cells are made of silicon, with varied designs that aim to maximise their efficiency in converting visible, infrared and UV light into electricity. Industrial production of silicon is expensive and energy-hungry, and therefore new technologies using alternative materials are being investigated: now, scientists at Queen Mary University of London (QMUL) have successfully demonstrated the use of biomass in nanostructured quantum dot solar cells.
Carbon quantum dots (CQDs) have previously been used in medical diagnostics and bioimaging, and are an emerging photovoltaic technology. These zero-dimensional ‘dots’ are spherical nanoparticles below 10nm in size, or <0.000000001 of a metre, which absorb light and have excitation-wavelength-dependent photoluminescence (PL) behaviour. The quantum dots are used to coat or ‘sensitize’ nanorods and act as semi-conductors in nanostructured solar cells.
CQDs can be made by a sustainable ‘bottom-up’ method which uses molecular precursors, in this case biological material from living or recently living organisms, or biomass. Since nanostructured solar cells currently use a pricey ruthenium-based dye, biomass-derived CDQs offer an attractive, far less costly alternative.
The team at QMUL School of Engineering and Materials Science used a one step hydrothermal carbonization process to produce CQDs from chitin and chitosan, major components of crustacean shells, and glucose – “three abundant and renewable precursors present in lignocellulosic biomass and most food-waste”. The CDQs were used to coat inexpensive zinc oxide nanorods to make a cheaper solar cell.
Still in the early phases of development, the shrimp shell solar cells have low efficiency. If this could be improved, the technology could be used to widen the use of solar power to wearable chargers for phones and other gadgets, as well as thin films to cover windows.
Dr Briscoe, a member of the research team, commented that “this could be a great new way to make versatile, quick and easy-to-produce solar cells from readily available, sustainable materials. Once we’ve improved their efficiency they could be used anywhere that solar cells are used now, particularly to charge the kinds of devices people carry with them every day.”
Briscoe, J., Marinovic, A., Sevilla, M., Dunn, S. and Titirici, M. (2015) Biomass-Derived Carbon Quantum Dot Sensitizers for Solid-State Nanostructured Solar Cells. Angewandte Chemie International Edition DOI: 10.1002/anie.201409290
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