Figure 2

I–V curves of n-Si/MoS₂ heterostructures upon light illumination of different wavelengthes: (a) 365 nm, (b) 450 nm, (c) 550 nm and (d) 650 nm. The power densities vary from 4 to 50 mW/cm². The I–V curves of n-Si/MoS₂ heterostructures present non-ideal photodiode-like behavior, where the reverse current increases with power density and the forward bias keeps almost constant regardless of power density. The weak photovoltaic effect was observed, where short current I_SC and open circuit voltage V_OC are small, as shown in insets of Figure 2a–d. (e) The band alignment at the interface between n-Si and monolayer MoS₂ at equilibrium, forward bias and reverse bias upon illumination. In the forward bias, photogenerated excitons could not be separated effectively due to the relatively larger barriers for holes and electrons transfer. However, the photogenerated holes could transferfrom the valance band of MoS₂ to n-Si, leading to the effective and efficient separation of excitons in the reverse bias.