Long-term performance and reliability of silicon heterojunction solar modules

The high-efficiency silicon heterojunction (SHJ) technology is now perceived mature enough to enter the Giga-Watt manufacturing scale with several players around the globe. The growth of the SHJ technology requires confidence from manufacturers, investors, and system developers about its reliability and long-term performance. In this work, we perform a literature survey collecting performance data (and performance loss rates [PLRs]) published for SHJ modules. Publications on this specific subject are still limited; however, enough available data exist to drive some preliminary conclusions. Despite a long list of caveats specific to this type of meta-analysis, when considering all published datasets, we obtain for SHJ modules median and average PLR values of 0.56%/year and 0.70%/year, respectively. These numbers are in line with PLR generally reported for field-deployed crystalline silicon (c-Si modules). We then apply a filtering procedure to distinguish what we perceive to be high-accuracy datasets from less accurate ones. This methodology is understandably arbitrary, but it helps increasing the robustness of the present analysis. Our refined analysis leads us to slightly higher PLR for SHJ modules: 0.80%/year and 0.83%/year for median and average values, respectively. These values fall between previously reported PLR of c-Si and thin-film modules. Additionally, we observe some mild correlations between the PLRs and the climatic conditions of the installation sites, even if we need to stress that for each climate, we find a large variability, including a PLR value as low as 0.29%/year. We complement the survey with information about the main failure modes reported in the literature for this technology and an analysis of the limits and caveats for this type of study. The most significant one is that the reported numbers refer—for the vast majority—to modules from just one manufacturer (i.e., the first company manufacturing and commercializing the SHJ technology). We finally point out that a deep understanding of the potential weaknesses of the technology—collected over the years—has led to several improvements in terms of reliability. A careful material choice and module design may in fact allow the SHJ technology targeting extended service lifetimes of 35+ years.