Researchers from UNSW have discovered that invisible light UV-induced breakdown in topcon sun cells accelerates, so that the same breakdown effects are produced as visible light but at a much faster speed. This can lead to significant open-circuit voltage losses and reducing cell efficiency.
Scientists from the University of New South Wales (UNSW) in Australia investigated the impact of UV-induced demolition (UVID) in solar cells based on tunneloxide-passivated contact (topcon) design.
Their analysis was particularly focused on the role of hydrogen and wavelength story in the UV range, which they described as ambiguous. “Uvid is increasing care because of the use of UV-transparent encapsulants,” said the main author of the research, Bram Hoex, said PV -Magazine. “This improves the efficiency of the module, but also exposes solar cells to UV radiation during the operation.”
The researchers explained that although there is still no scientific consensus on the causes of UVID, the most important assumption is that it is caused by photons with an energy higher than 3.4 EV, which break the bonds between silicon (SI) and hydrogen (h), creating recombination-active bump bindings. This in turn, Create recombination losses, which mainly influence the open-circuit voltage of the cell.
The novelty of the study is represented by the fact that the scientists have considered the entire UV radiation spectrum for the first time, which includes UV-a radiation, that has that wavelengths between 315-400 Nm and is closer to visible light and UV-B radiation, that is An energetic, invisible form of solar radiation with wavelengths between 290-320 Nm.
“We Used UV-B for Accelerated Testing of Topcon Cells in Lab Conditions, Enabling Faster Reliability Assessments Without Introding New Failure Modes,” Hoex Explained, Noting That UV-B is Commonly Not Percceived As A Major Concerny-BaGAX-BAIX Radiation, Leading to the Idea That Topcon Module Are Fully Protected by this Potential relegation mechanism.
However, the race for more efficient products is the pushing of manufacturers to use encapsulating agents with a higher UV transmission, which increases the risks. “UV-B can significantly break down the passivation of the top cone cells of topcon cells, which leads to increased surface recombination,” Hoex explained further. “It can accelerate UVID in topcon sun cells, which produces the same breakdown effects as UV-A, but with a much faster speed.”
For their analysis, the academics used on the market available bifacial top concon cells based on N-type Czochralski (CZ) silicon waffles of 182 mm x 182 mm and with a thickness of 140 μm. The devices had a drill-different emitter on both sides, which was passivated by a 5 Nm Multiple stack of aluminum oxide (ALOX)) deposited by atomic layer (Ald) and a silicon nitride (sinX) Low anti-reflection coating.
The researchers also used a UV-a and UV-B lamp system at a temperature of 60 ° C to deliver a total dose of 61.1 kWh/m2 for UV-B and 49 kWh/m2 for UV-a radiation for testing. In particular, they analyzed the behavior of the cells before and after hydrogen delivery from the Sinx layer.
“We have determined that degradation mainly takes place on the front surface of the topcon, driven by SI-h binding breaking and hydrogen re-distribution, the increase of surface recomination, in which the rear surface shows a strong UV resistance as a result of the doped poly-si-layer absorbin, said no light and elevated,” said not, “said,” said no-ra-370-fotonon, “” said, “said,” said, “said,” said, “said,” said, “said,” note-to-370-foton. ” (Letid) was observed under UV-exposure. “UV changes hydrogen dynamics in a way that suppresses this defect.”
The data showed that the UV radiation breaks the SI-H bindings on the Alox/(P+) SI interface, resulting in an increase in hydrogen ions. “However, the exact mechanism of this interaction and the long -term effects of changed hydrogen distribution require further research,” the scientists emphasized.
The research group said that the UV-B industry should consider in accelerated tests of topcon cells in laboratory conditions, which enable faster reliability assessments without introducing new failure modes. In addition, manufacturers must use the UV protection behind the back by maintaining sufficient poly-si thickness in the design, while using UV-resistant Inkapsulants and UV filtering strokes to control the hydrogen distribution.
Their findings are available in the study “UV-induced breakdown in topcon sun cells: hydrogen dynamics and impact of UV golf length“Which was recently published in Solar energy materials and solar cells.
Previous research by UNSW pale Relegation mechanisms of industrial-concon-zonnemodules encapsulated with ethylene vinylacetate (EVA) under accelerated damp conditionsAs well as the vulnerability of Topcon sun cells to contact corrosion and three types of Topcon sun module disruptions that were never detected in perc panels. In addition, UNSW scientists investigated the breakdown of topcon sun cells induced by sodium under exposure to moist heating and the role of ‘hidden contaminants’ in the demolition of both top-cone and hetero junction devices.
In addition, another UNSW study recently assessed the impact of soldering flux on heterojunction sun cells and discovered that the composition of this component is the key to prevent important cracks and significant peeling.
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