Investigation on light elevated temperature-induced degradation of PERC PV modules

The Passivated Emitter and Rear Contact (PERC) technology for PV modules was highlighted in the market in 2019, increasing commercial efficiency to 22.4% and taking over 50% of production capacity[1]. This technology is expected to continue its market dominance over the next three years. Meanwhile, a study to investigate the effects of light and elevated temperature-induced degradation (LeTID) was conducted, and the standard technical specification for LeTID (IEC TS 63342:2022) was issued. To increase understanding of LeTID, this study was implemented by testing commercial PERC PV modules following IEC TS 63342:2022. Table 1 shows the STC results of the PV modules tested before the LeTID test in this study.

Table 1: Properties of PV modules at STC condition before LeTID testing.

Figure 1 shows the LeTID results from the 1^st to the 10^th cycle. The power decreased after the 2^nd test cycle and increase after the 4^th test cycle for polycrystalline silicon. A similar pattern was observed for monocrystalline silicon, with the power returning after 6^th test cycle. Typical electroluminescence (EL) image to illustrate the change in microstructure at the 4th test cycle shows in Figure 2. Our test results show the power degradation pattern following the LeTID performance loss, but with only a small percentage of degradation. Furthermore, the analysis of changes in microstructure and electrical properties will be reported.