Silicon-based solar modules dominate the current market. However, they are expensive and have a high carbon footprint.
A new generation of modules made using a compound called cadmium telluride (CdTe) is emerging, and more than 25 GW have been installed.
The efficiency of solar panels refers to the ability of panels to convert solar energy into electrical energy.
Experts are seeking to improve the efficiency of CdTe modules because it has the potential to be competitive in terms of efficiency, but the manufacturing cost is lower than that of silicon-based modules using single crystal silicon (c-Si).
scrapped CdTe modules. The carbon footprint of CdTe is also half of that of c-Si modules, and it ensures the recycling of
The efficiency of untreated CdTe is very low, usually only about 1%. However, when CdTe is treated with chlorine (including treating CdTe with cadmium chloride at 420oC for 20 minutes), its efficiency rises sharply. The record battery efficiency is 22%.
Dr. Pooja Goddardard and Professor Roger Smith of Loughborough University, and Dr. Peter Hatton and Dr. Michael Watts (PhD graduates of Loughborough University) simulated for the first time the mechanism by which chlorine improves the efficiency of CdTe.
The research was done in collaboration with the experimental research team of Professor Mike Walls at the Loughborough Renewable Energy System Technology Center (CREST).
The results of the study published today in Nature Communications can improve the understanding of how chlorine can enhance electrical performance and lead to further adjustments, leading to higher efficiency (> 25%). This will help CdTe solar modules produce lower cost electricity.
In trying to understand why chlorine can increase efficiency, the main observation of previous studies was that defects (called “stacking faults”) were removed after chlorine treatment.
For a long time, it has been believed that removing stacking faults is the reason for improving efficiency. However, the theoretical calculations of the Loughborough team show that stacking faults have no effect on cell efficiency.
The team’s previous research has shown that, on the contrary, it is the material regions called “grain boundaries”, that is, crystals in different directions are connected together, which leads to low battery efficiency.
In their latest research, Dr. Goddard’s team used quantum mechanics methods to understand the role of chlorine in improving efficiency and eliminating stacking faults.
The grain boundaries are very complex and full of defects, which can act as electron traps (subatomic particles that are the main carriers of electricity in a solid), making these regions “active”.
In a process called “passivation”, chlorine can inactivate some traps and make the grain boundaries less active, thereby increasing the efficiency of CdTe.
The new paper shows that if there is enough chlorine in the grain boundaries, it will trigger the cascade mechanism, thereby eliminating stacking faults in the structure.
“Although the disappearance of stacking faults is not the cause of the increase in efficiency, if they disappear, it is a signal that the CdTe battery will have good performance. This has never happened before,” Dr. Goddard was asked The importance of paper.
She continued: “We are pleased to publish our work in Nature Communications, which demonstrates our hypothesis on how chlorine can not only improve the efficiency of CdTe batteries, but also eliminate key flaws.
“The next step will be to see how to further improve the efficiency of >25% by doping CdTe with other elements. Our continued cooperation with CREST will also seek to optimize the interface between CdTe and CdTe. point.
“Every small improvement in efficiency means that the technology has become more competitive with current silicon technology.”
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