Revealing the Interface Degradation of Monolithic Perovskite/Silicon Tandem Photovoltaics

Perovskite/silicon (Pero/Si) tandem solar cells are rapidly advancing toward high-efficiency photovoltaic deployment; yet, their long-term stability remains a critical bottleneck. Here, we systematically investigated interface degradation in monolithic Pero/Si tandem architectures based on two leading configurations: perovskite/tunnelling oxide passivated contact solar cells (Pero/TOPCon) and perovskite/heterojunction solar cells (Pero/HJT). Illumination and damp heat tests (following the ISOS-L-3 and ISOS-D-3 protocols) indicated that both tandem devices suffered from a pronounced interfacial instability. By revealing the buried interface properties with a multimodal interface characterization toolkit, we identified two degradation pathways: (i) perovskite decomposition at the buried interface driven by ion migration and deprotonation, and (ii) interfacial degradation of the silicon substrate exacerbated by ion invasion and hydrogen effusion. It is highlighted that the amorphous nature of the interconnection layers facilitated ion/hydrogen permeation and defect formation. Our work elucidated the additional interface degradation path of Pero/Si tandem, thus highlighting the importance of interconnection contact quality for developing durable Pero/Si tandem photovoltaics.