Conventional ionic ferroelectrics enable exciton control through switchable polarization but face challenges like high switching barriers and fatigue. Sliding ferroelectricity in van der Waals structures is capable of addressing these limitations with low energy consumption and excellent endurance, presenting a promising platform for excitonic applications. In this work, we construct a Janus bilayer MoSeTe and investigate its exciton-related optoelectronic properties using the $\mathit{GW}$–Bethe-Salpeter equation method. Along the AB-BA sliding path, the system exhibits low energy barriers (3.56 meV/atom) and high polarization (1.147 pC/m), accompanied by an exchange between layers in their contributions to the valence band maximum and conduction band minimum. This leads to a transition of the first bright excitonic state from the sliding layer to the fixed layer. Notably, because of band degeneracy and hybridization, the nonpolar state that emerge during the sliding process exhibits enhanced and localized excitonic absorption as well as interlayer exciton components, which are absent in both AB and BA stackings. This work highlights the considerable potential of sliding ferroelectricity in modulating exciton dynamics and provides a theoretical basis for the design of low-power, high-performance optoelectronic devices.

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• Excitons
• Ferroelectricity
• 2-dimensional systems
• Bilayer films
• Ferroelectrics
• Janus materials
• First-principles calculations
• GW method