Off-the-grid in style: researchers produce efficient colour solar cells
The 'rainbow sun' shown to us by NASA's Solar Dynamics Observatory. Credit: NASA/SDO
Thursday, February 12, 2015, 9:57 AM - Looking to take yourself 'off the grid', but standard black solar panels clash with the design aesthetic of your home? A new development could be the answer to your problem, as scientists have designed solar panels that come in an array of colours.
Some of the most common, fastest-advancing and cheapest types of solar cells are ones that use a layer of material called a perovskite absorber to convert sunlight into electricity. In just five years, researchers have raised the efficiency of this kind of solar cell from from less than 4 per cent to over 20 per cent, and this will likely continue to increase quickly with time.
Although efficient, there are some limitations to the application of these cells, since there's very little colour variation to them. Other types of cells can offer more colour range, but at efficiencies far lower than perovskite cells can offer. Colour may seem like an unusual thing to count as a limitation when it comes to something so functional, but having a wider range of colours would allow these cells to find a much wider range of applications. Rather than just fields or roofs covered in cells that range from black to red-brown to yellow, solar cells could double as signs, they could be incorporated into the roofs of cars and other vehicles, into building windows and even something simply more aesthetically pleasing for the average person to install on their home.
To this end, researchers have designed solar cells that can be made into different colours, by layering the perovskite absorber overtop of a substance known as a photonic crystal - which is composed of alternating layers of silicon dioxide - SiO2 - (you can find this in silica packets you find inside shoe boxes, for example) and titanium dioxide - TiO2 - (the UV blocker in sunscreen). Vary the thickness of these layers in the photonic crystal, and the colour of the cell changes.
The interior structure of the new solar cells and the array of real colours that can be produced so far. Credit: H. Snaith, H. Miguez, et al., edits by Scott Sutherland.
These new cells are not perfect, of course.
With the photonic crystal layer added, it reduces the efficiency of the cells, so that the standard 20 per cent is reduced, ranging from around 4 per cent for red cells, up to just shy of 9 per cent for blue.
However, this meets or exceed the efficiency of other types of colour cells, and with further research and development into increasing the efficiency of standard cells, this will carry over to increase the energy output of these colour perovskite cells as well.