The kesterite represents the end of hydrogen in the world and a step closer to unlimited energy.
Photovoltaic devices (PV) are products capable of transforming solar light into electrical energy, a tool that is expanding more and more given the context of energy transition we are in.
With increasing popularity, renewable energy engineers worldwide are working to identify materials and procedures that could help further reduce the cost of solar technologies, while increasing their energy conversion efficiencies (PCE) even more.
Kesterite: a promising material in search of unlimited energy
In this context, a highly promising material stands out for the development of photovoltaic devices: wide bandgap kesterite Cu2ZnSnS4 (CZTS). It is a semiconductor that exhibits a large energy gap and, therefore, could absorb light more efficiently.
Unlike silicon, which is currently the main material used to manufacture photovoltaic technology, CZTS is not a toxic resource and is composed of elements abundant on Earth. Therefore, it could be used for the development of more sustainable and affordable solar cells.
Challenges and solutions
Despite its clear advantages, CZTS solar cells have so far shown much lower efficiencies than silicon, with a maximum recorded efficiency of 11%.
This limited performance is largely due to a process called carrier recombination, which involves the recombination of photo-generated electrons and holes before they can be captured to produce electricity.
Research and hydrogen annealing
Under these circumstances, a group of researchers from the University of New South Wales in Sydney analyzed the possibility of mitigating the effects of carrier recombination in kesterite solar cells using the hydrogen annealing technique.
They published a paper in Nature Energy, where they showed that this technique could contribute to an improvement in carrier collection in these solar technologies, through the redistribution of oxygen and sodium in the CZTS layers.
“Our work was inspired by the need to identify a sustainable, low-cost, and environmentally friendly material for next-generation solar technologies,” stated Kaiwen Sun, lead author of the paper, to Tech Xplore.
“CZTS is a particularly promising candidate as the top cell in tandem solar cell architectures due to its tunable bandgap, stability, and the use of non-toxic elements abundant on Earth. However, a key challenge has been to improve the collection efficiency of this material,” Sun pointed out.
Benefits of hydrogen annealing
Hydrogen annealing is a technique that heats devices in a hydrogen-charged atmosphere. To achieve this, the researchers developed a simple and scalable system for annealing.
“Hydrogen plays a crucial role in our method, by redistributing sodium within the material and passivating defects, particularly near the absorber surface. This process significantly enhances carrier transport and collection, key factors in achieving high-performance devices,” Sun clarified.
By improving these properties, our approach strengthens the position of CZTS as a top cell material practical and cost-effective in tandem solar cells, capable of efficiently pairing with silicon for a broader utilization of the solar spectrum.
The future of unlimited energy
As part of the work, Sun and the rest of the specialists used a proposed hydrogen annealing mechanism on a cadmium-free CZTS solar cell. They discovered that this perspective significantly boosted the solar cell, achieving a new record efficiency of 11.4%.
The kesterite marks the end of hydrogen in the world and conventional solar panels, the missing step to achieve infinite energy. The same infinite energy that is sought to be touched with the Holy Grail of the United States.
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