Scientists from Chinese solar manufacturer Trina Solar have proposed a new classification of ultraviolet-induced degradation (UVID) in TOPCon solar cells, distinguishing between reversible (r-UVID) and irreversible (ir-UVID) degradation. The aim is to improve reliability assessments, standardize testing procedures, and better predict long-term performance under real-world operating conditions.
The research team explained that the proposed r-UVID and ir-UVID categories are aligned with the recovery procedures envisaged in the forthcoming International Electrotechnical Commission (IEC) technical specification IEC TS 63624-1, which is being developed to standardize laboratory testing protocols for assessing UV-induced degradation in crystalline silicon solar modules.
“By aligning its proposed definitions with the forthcoming IEC standard, the paper introduces a classification that aims to establish a common language across standardization, reliability testing, warranty assessments, and project financing, enabling more consistent evaluations of long-term performance risks and helping distinguish temporary, recoverable power losses from permanent degradation that affects actual energy yield,” corresponding author Zhiwei Li told pv magazine.
The researchers explained that a defining feature of UVID in TOPCon solar cells is its pronounced metastability. Following UV exposure, cells can experience further performance losses during dark storage, primarily driven by a decline in open-circuit voltage and characterized by double-exponential degradation kinetics. Much of this additional degradation, however, is reversible and can be recovered through light soaking or thermal annealing, which promote hydrogen redistribution and changes in charge trapping at passivation interfaces.
“Field tests have confirmed that this metastable loss does not affect actual outdoor energy yield, as daily sunlight enables dynamic recovery,” the researchers said.
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