Heating up the heterojunction-LID conversation

• Scientists led by the University of New South Wales have checked into the long-lasting deterioration of silicon-heterojunction. Their searchings for recommend that lighting at heats can really boost cell efficiency, however also runs the risk of triggering multiple light-induced degradation devices if not meticulously controlled.

For lots of, heterojunction (HJT) modern technology stands for the future of silicon PV. However even as the modern technology gets ready for mainstream manufacturing, issues continue to be about the deterioration mechanisms which might affect the long-lasting efficiency of such cells in the field.

" A successful boost in SHJ [silicon heterojunction] uptake will certainly depend mostly upon the capacity of the cells to preserve the superb surface passivation instrumental to their high performances, over the life time of the panels," said scientists at Australia's University of New South Wales (UNSW). "Thus, it is necessary that the long-lasting stability of SHJs is effectively recognized as well as potential power loss mechanisms are recognized as well as minimized."

Previous researches have actually kept in mind both destruction as well as succeeding recovery systems affect cell passivation layers on exposure to light and also warmth. While the physics behind the devices is not well comprehended, it is generally accepted the existence of hydrogen plays a key duty.

Light as well as dark annealing

The UNSW group subjected commercially-available HJT cells to varying levels of temperature between 25 and 180 levels Celsius and to light intensity of 1-40 kWh/m ² over various timeframes. Full details of the experiments can be located in the paper Investigation of light-induced deterioration in N-Type silicon heterojunction solar cells during brightened annealing at elevated temperatures, released in Solar Energy Materials and Solar Cells and on the ScienceDirect website.

The results verified HJT cells are prone to light-induced destruction (LID) which can bring about the loss of up to 0.8% outright performance, reliant upon temperature level and also light strength. Under 1-sun illumination, the degradation device began to show itself at temperature levels over 85 levels Celsius and also increased with the temperature.

After 5 minutes at 160 degrees Celsius, cells showed a typical loss of 0.8% absolute effectiveness. Nevertheless, longer exposure initiated a recuperation mechanism, with the performance loss narrowed to 0.15% after 2 hours at 160 levels Celsius and also under 1 sun illumination. Boosting the light intensity was discovered to speed up the recuperation phase with no discernible impact on degradation. "These outcomes recommend that fast enhancement of SHJ solar cell performance can be acquired making use of illuminated annealing at raised temperature levels," the group ended. "However, these exact same processes can additionally be damaging to cell performance otherwise carefully maximized."

More work is required to understand the long-term effects of lit up annealing, the team noted, in addition to bring direct exposure times down to a degree viable for manufacturing.

Ultimately, the researchers stated, a fuller understanding of the LID devices at work on HJT cells is required. "Further researches are required to check out the main aspects and also causal device( s) underlying the observed LID behavior," the paper concluded, "as well as just how finest to prevent defect activation or accomplish robust mitigation with brightened annealing treatments."