Stabilizing Copper‐Metallized Silicon Heterojunction and Hybrid Back‐Contact Solar Cells Against Light‐Induced Degradation

The replacement of expensive silver with copper (Cu) electrodes is a critical pathway for reducing the cost of silicon heterojunction (SHJ) and hybrid back‐contact (BC) solar cells. Electroplated copper grids enable high performance in SHJ and hybrid BC, yielding efficiencies of 25.71% and 26.95%, respectively, representing a 0.25% absolute gain for SHJ over silver references. A critical barrier to adoption is copper‐related light‐induced degradation (LID) which severely affects devices with n ‐type microcrystalline silicon ( n ‐µc‐Si) electron transport layers, inducing an efficiency loss of about 1.21%. We find this degradation stems from electric field‐ and temperature‐driven Cu migration, through the n ‐µc‐Si and transparent conductive oxide (TCO). To address this issue, we develop a stabilization strategy using an oxygen‐doped n ‐µc‐SiO X layer combined with a post‐deposition anneal of TCO. This approach improves optical transmittance, and strengthens the barrier against copper diffusion. Consequently, the light‐induced efficiency loss is minimized to only 0.14% for Cu‐electrode SHJ, which also gain an additional 0.12% in initial efficiency. Cu‐electrode hybrid BC exhibit similarly stability with 0.17% degradation. This work contributes to the development of high‐efficient, stable, and low‐cost silicon solar cells by providing key insights and practical strategies for implementing copper metallization.