Molybdenum oxide ( \(MoO_x\) ), a wide band-gap material with low optical absorption, has emerged as a promising candidate for the hole-selective front contacts for silicon solar cells. However, the carrier selectivity is limited by the absence of a sufficiently high electron barrier. In this study, numerical simulations demonstrate that incorporating an ultra-thin aluminum oxide tunnel layer ( \(\le\) 2 nm) enhances the hole selectivity in \(MoO_x\) -based front contacts. Introducing the tunnel layer at the \(MoO_x\) /c-Si (n) interface resulted in a relative increase of 5.36 % over the control cell efficiency of 17.77 %. A systematic variation of the energy-band alignment of the tunnel layer revealed that the observed performance enhancement is primarily due to the additional conduction band energy barrier formed by the tunnel layer. A strong influence of the tunnel layer thickness, interface defect density, and pinholes through the tunnel layer on the open-circuit voltage was observed. Subsequently, the tunnel layer was also found to reduce the temperature sensitivity of the solar cell performance. The tunnel layer reduced the magnitudeof the simulated \(P_{max}\) temperature coefficient of the structure from −0.39 %/°C to −0.15 %/°C, signifying its role in developing high-efficiency silicon solar cells.
