Study on the Thermal Stability of Molybdenum Oxide‐Passivated Silicon Solar Cells

Dopant‐free heterojunction (HJ) solar cells are known for their simple process conditions and low parasitic absorption. However, stability issues remain one of the major obstacles for further development of cells with transition metal oxides (TMOs). Therefore, this research demonstrates the mechanism of thermal annealing degradation effects on TMOs/silicon (Si) HJ, namely, the infiltration of oxygen from air and the bidirectional diffusion of oxygen from TMOs, by investigating a typical molybdenum oxide (MoO x )/Si contact. A dense Au interlayer is introduced to block the interdiffusion of oxygen from the MoO x /Si interface and its surrounding environment. As a result, the dense layer slows down the interfacial oxidation of MoO x /Si and the degradation of the MoO x work function, thus improving the stability of the MoO x /Si HJ to 200 °C. The diffusion of oxygen from MoO x to the MoO x /Si interface will be critical to further promote the thermal stability of the devices thereafter, especially for the cells with i ‐a‐Si:H layer as the passivation layer. To attain stable dopant‐free cells with MoO x , it is crucial to prevent oxygen diffusion into Si while maintaining a high MoO x work function and a thin SiO x layer at the interface.