Interfacial Engineering Enables Over 23.8% Efficiency Crystalline Silicon/Transition Metal Oxide Heterojunction Solar Cells

Abstract Replacing heavily doped silicon layers in crystalline silicon (c‐Si) solar cells with wide‐bandgap transition metal oxides (TMO) offers significant potential for reducing parasitic optical absorption, streamlining fabrication processes, and enhancing device efficiency. However, the interfacial passivation and contact properties of c‐Si/TMO heterojunctions remain key bottlenecks to further performance improvement. In this work, interface engineering is applied to simultaneously optimize both the c‐Si/TMO and TMO/silver (Ag) interfaces within the contact structure, aiming to improve the overall passivating contact performance. A very thin molybdenum dioxide (MoO 2 ) layer with low work function is introduced at the TMO/Ag interface to tailor the band alignment and reduce contact resistance. Meanwhile, a hydrogen‐rich aluminium oxide (Al 2 O x ) layer is partially inserted at the c‐Si/TMO interface to suppress interfacial carrier recombination. By employing these interface modification strategies, c‐Si/TMO heterojunction solar cells are successfully fabricated with power conversion efficiencies surpassing 23.8%, which highlights the considerable promise of TMOs as high‐performance hole‐selective contacts in c‐Si photovoltaics.