Passivating Contacts‐Related Ultraviolet‐Induced Degradation in Silicon Heterojunction Solar Cells

Hydrogen (H) is essential for the high performance of advanced crystalline silicon (c‐Si) solar cells. Recently, H‐related ultraviolet‐induced degradation (UVID), which can compromise module stability, has attracted increasing attention from the photovoltaic (PV) industry, yet its underlying mechanisms remain incompletely understood. Here, the severity of UVID in silicon heterojunction (SHJ) solar cells is shown to depend strongly on the illuminated‐side passivating‐contact design, with transparent passivating contacts (TPCs) exhibiting markedly larger losses in open‐circuit voltage ( V OC ), short‐circuit current ( J SC ), and fill factor (FF) than conventional hydrogenated amorphous silicon (a‐Si:H)‐based SHJ contacts. Combined material characterizations and device analysis support a picture in which the high transparency of TPC shifts UV energy deposition toward the c‐Si near‐interface region, where UV‐driven Si─H bond dissociation increases interfacial recombination and degrades chemical passivation. In parallel, UV exposure induces a pronounced resistivity increase in the hydrogenated nanocrystalline silicon carbide (nc‐SiC:H) contact stack, consistent with local microstructural/electronic disorder and the possible involvement of enhanced sub‐bandgap absorption, thereby raising series resistance ( R s ) and limiting carrier collection. Collectively, these findings link contact optical transparency, H‐related bond dynamics, and nc‐SiC:H transport degradation to the distinct UVID signatures of SHJ architectures.