MoOx/V2Ox bilayer hole-selective passivating contact for silicon heterojunction solar cells

Abstract

The molybdenum oxide (MoOx) hole-selective passivating contact for crystalline silicon (c-Si) solar cells is highly susceptible to degradation upon exposure to ambient air during both device fabrication and operation. In this work, we introduce a V2Ox capping layer onto MoOx via continuous thermal evaporation without breaking the vacuum. As a result, compared to the air-exposed reference (4.69 eV), the protected MoOx exhibits a significantly increased work function of 5.54 eV. This enhancement is attributed to the formation of a V-doped MoOx interfacial region, which chemically suppresses oxygen vacancies and stabilizes a higher Mo6+ content. Also, the average implied open-circuit voltage of a-Si:H(i)/MoOx/V2Ox stacks is enhanced from 722.5 to 732.4 mV due to improved field-effect passivation. Meanwhile, the contact resistivity is significantly reduced from 185 to 122 mΩ cm2 upon insertion of the V2Ox layer. Consequently, the silicon heterojunction solar cells featuring front full-area a-Si:H(i)/MoOx/V2Ox contacts achieve an improved efficiency of 22.8%, with an open-circuit voltage of 727.8 mV, a short-circuit current density of 39.9 mA/cm2, and a fill factor of 78.6%. Furthermore, the devices demonstrate markedly enhanced long-term stability, retaining over 96% of their initial efficiency after 2000 h of exposure to ambient air. The MoOx/V2Ox bilayer strategy not only enhances the performance of MoOx-based hole-selective passivating contacts but also offers a practical route to improved operational robustness.