Driving reliability in industrial TOPCon solar cells and modules:

Insights into damp-heat challenges and pathways to solutions

Xinyuan Wu¹, Xutao Wang¹, Jiexi Fu¹, Wei Wu², Weiguang Yang², Yan Zhang², Jing Yuan²,

 Jianjun Nie², Feng Li², Lin Lv², Bram Hoex¹

¹ School of Photovoltaic and Renewable Energy Engineering, UNSW, Australia

² Jolywood (Taizhou) Solar Technology Co., Ltd.

E-mail: xinyuan.wu@unsw.edu.au

Abstract

Tunnel oxide passivated contact (TOPCon) technology has become the dominant photovoltaic cell architecture, surpassing 55% of global market share in 2024 and expected to expand further in the coming years. Although highly efficient, TOPCon modules are particularly prone to damp-heat (DH) stress, where metallization and contact failures frequently occur. The application of low-cost encapsulation materials, such as ethylene-vinyl acetate (EVA) with back-sheet structures, amplifies these risks, as hydrolytic degradation of EVA generates acetic acid that accelerates corrosion. 

In this work, we systematically investigate DH-induced degradation pathways in industrial TOPCon solar cells and glass–backsheet modules fabricated with conventional Ag/Al paste and with customized low-Al Ag paste combined with laser-assisted firing (LAF). At the cell level, Ag/Al paste contacts show severe Al oxidation and interfacial corrosion, leading to significant increases in series resistance, while LAF cells with low-Al or Al-free pastes maintain stable contact resistivity and demonstrate superior reliability. Module-level testing confirms that EVA-encapsulated modules with Ag/Al paste suffer substantial power loss (~37%_rel Pmax reduction after 1000 h DH85), whereas LAF modules exhibit markedly improved stability (~6%_rel loss).

Mechanistic analysis identifies Al instability, glass frit dissolution, and rear-side Te compound corrosion as primary degradation drivers. From this work, we also propose methods for cell-level accelerated testing that provide rapid and reliable feedback to industrial R&D, enabling faster optimization of materials and processes. These insights highlight laser-assisted firing, combined with optimized metallization and glass frit design, as a practical pathway to cost-effective and durable TOPCon modules.

Keywords: Photovoltaics; Tunnel oxide passivated contact (TOPCon); Damp-heat stability; Silicon solar cells; Metallization reliability; Laser-assisted firing; Laser-enhanced contact optimization; Corrosion

Biography:

Xinyuan Wu is a postdoctoral fellow at School of Photovoltaics and Renewable Energy Engineering, UNSW Sydney, Australia. His research focuses on the industrial solar cell’s reliability and performance enhancement combining nano-scale engineering. He was the process engineer on front surface passivation optimization at Jiangsu Leadmicro Nano-Equipment Technology Ltd. His research work has been published in several international conferences and peer-review journals.