Results from an international interlaboratory study on light‐ and elevated temperature‐induced degradation in solar modules

Abstract

This paper reports the results of an international interlaboratory comparison study on light‐ and elevated temperature‐induced degradation (LETID) on crystalline silicon photovoltaic (PV) modules. A large global network of PV module manufacturers and PV testing laboratories collaborated to design a protocol for LETID detection and screen a large and diverse set of prototype modules for LETID. Results across labs indicate the reproducibility of LETID testing is likely within ±1% of maximum power (PMP). In intentionally engineered LETID‐sensitive modules, mean degradation after the prescribed detection stress is roughly 6% PMP. In other module types the LETID sensitivity is smaller, and in some we observe essentially negligible degradation attributable to LETID. In LETID‐sensitive modules, both open‐circuit voltage (VOC) and short‐circuit current (ISC) degrade by a roughly similar magnitude. We observe, as do previous studies, that LETID affects each cell in a module differently. An investigation of the potential mismatch losses caused by nonuniform LETID degradation found that mismatch loss is insignificant compared to the estimated loss of cell ISC, which drives loss of module ISC. Overall, this work has helped inform the creation of a forthcoming standard technical specification for LETID testing of PV modules, IEC TS 63342 ED1, and should aid in the interpretation of results from that and other LETID tests.

Assessing the long-term stability of laser enhanced contact optimization (LECO) treated PERC cells in PV modules by extended indoor and outdoor durability tests

“…Yet, there is a permanent I SC loss or the time for regeneration is too short which indicates defects whose kinetics have longer time scales like Light-elevated Temperature Induced Degradation (LETID). Here the regeneration takes 3-4 weeks with a current injection level of I SC at 85 °C [8]. The slope of the curves also shows an increased series resistance.…”

PV Lifetime Project (2021 NREL Annual Report)

“…However, a pronounced LeTID sensitivity was identified via indoor test screening. Two samples showed a recoverable 3%-5% LeTID performance change in response to the LeTID screening procedure of Karas et al (2022).…”

The effect of partial shading on the reliability of photovoltaic modules in the built-environment

“…As the suspected degradation modes in this study (i.e. light-and elevated-temperature-induced degradation (LeTID) and/or ultraviolet (UV) radiation-induced degradation [41,42]) are unrelated to shadow masks, this will be the focus of a future study comparing the performance of the same module technologies in open-rack and heat blanket (outdoor accelerated-ageing) configurations in addition to the modules in this study.…”