Carrier Transport and Performance Limiting Mechanisms in MoS 2 /c‐Si Heterojunction Solar Cells

The work presents a comprehensive numerical study on the thickness‐dependent performance of n‐MoS 2 /i‐a‐Si:H/c‐Si(p) heterojunction solar cells using the AFORS‐HET simulation platform. The physical mechanisms controlling device behaviors are analyzed for monolayer, bilayer, multilayer and bulk‐like MoS 2 . The current density–voltage ( J – V ) characteristics reveal that the monolayer device has the highest efficiency (~22.08%) with the best open‐circuit voltage ( V oc ) and short‐circuit current density ( J sc ). With increasing MoS 2 thickness, progressive degradation of performance is observed. Capacitance–voltage ( C – V ) analysis shows that ultrathin MoS 2 layers allow efficient charge separation and stronger electric‐field penetration, whereas electrostatic screening occurs in thicker layers. The defect study assumes a continuous bandgap trap distribution with large capture cross‐sections (~10 −14 cm 2 ). Strong defect tolerance is observed over all configurations, with noticeable recombination‐induced degradation only at extreme defect densities (~10 18 cm −3 ). Temperature‐dependent analysis (300–330 K) further suggests improved thermal stability of ultrathin devices. External and internal quantum efficiencies (EQE‐IQE) provide evidence of dominant loss mechanisms, including parasitic optical absorption, decreased carrier mobility, transport bottlenecks, and increased defect‐mediated recombination. These factors prevent efficient carrier collection, especially in the short‐wavelength regime. Results demonstrate the benefits of ultrathin configurations for high‐efficiency 2D material‐integrated heterojunction solar cells.