The sun provides us with enough energy to meet the current global energy demand 10,000 times over. To use just 1% of this would end the current energy crisis. However, as luck would have it, we don’t have the means – scientifically, financially and technologically – to do this.

Of course, we are trying, and one thing that’s catching on is to install photovoltaic cells onto rooftops – an area that faces the sun at all times but currently doesn’t serve much of a purpose. Unfortunately, current technologies are prohibitively costly and so scientists are attempting to lower costs by creating ceramic tiles that can perform photovoltaic action, so-called ‘solar tiles’. In addition to being able to generate power, solar tiles can also take advantage of the photocatalytic activity of titanium dioxide nanoparticles to decompose atmospheric pollutants.

However, due to challenges such as selecting a suitable solar cell material and transferring technology from the lab to industry, there have not been any successful attempts at turning this concept into reality.

Hugo Aguas, Rodrigo Martins and their research group at Universidade NOVA de Lisboa and UNINOVA have successfully fabricated solar tiles and demonstrated market viability with a cost estimation. The researchers decided to use the tried-and-tested thin film silicon solar cells, depositing them onto ceramic tiles using the currently available plasma-enhanced chemical vapour deposition technique.

Part of a building roof and facade with integrated solar tiles

Firstly, a SiOx interfacial layer was deposited. Then back and top contacts of gallium zinc oxide and indium zinc oxide, respectively, were deposited on top of this along with the n–i–p silicon junction cell. Individual tiles are then interconnected using male pins and female sockets, in a manner not dissimilar to Lego bricks, at the positions where the tiles would overlap with each other.

Their new solar tiles were able to achieve a 5% conversion efficiency and 80% quantum efficiency. However, the researchers stress that the cell’s structure is not yet fully optimised and there could be further improvements in future.

Yuandi Li

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