Electrical and photovoltaic characteristics of MoS2/Si <i>p-n</i> junctions

TLDR

MoS2 thin films on p‑type Si form p‑n junctions whose electrical and photovoltaic behavior depends on their Fermi level (~4.65 eV) and band gap (~1.45 eV). MoS2 films were sputtered onto p‑type Si to form p‑n junctions, and their current–voltage characteristics were measured and analyzed using the determined Fermi level and band gap to explain the electrical and photovoltaic behavior. Raman spectroscopy revealed E12g and A1g modes, the junction showed a 0.2 V turn‑on rectifying J‑V curve dominated by diffusion and recombination currents, and under 15 mW cm⁻² illumination it produced 3.2 mA cm⁻² short‑circuit current, 0.14 V open‑circuit voltage, 42.4 % fill factor, and 1.3 % efficiency, indicating potential for high‑efficiency Si‑based photovoltaics.

Abstract

Bulk-like molybdenum disulfide (MoS2) thin films were deposited on the surface of p-type Si substrates using dc magnetron sputtering technique and MoS2/Si p-n junctions were formed. The vibrating modes of E12g and A1g were observed from the Raman spectrum of the MoS2 films. The current density versus voltage (J-V) characteristics of the junction were investigated. A typical J-V rectifying effect with a turn-on voltage of 0.2 V was shown. In different voltage range, the electrical transporting of the junction was dominated by diffusion current and recombination current, respectively. Under the light illumination of 15 mW cm−2, the p-n junction exhibited obvious photovoltaic characteristics with a short-circuit current density of 3.2 mA cm−2 and open-circuit voltage of 0.14 V. The fill factor and energy conversion efficiency were 42.4% and 1.3%, respectively. According to the determination of the Fermi-energy level (∼4.65 eV) and energy-band gap (∼1.45 eV) of the MoS2 films by capacitance-voltage curve and ultraviolet-visible transmission spectra, the mechanisms of the electrical and photovoltaic characteristics were discussed in terms of the energy-band structure of the MoS2/Si p-n junctions. The results hold the promise for the integration of MoS2 thin films with commercially available Si-based electronics in high-efficient photovoltaic devices.