The role of MoS2 as an interfacial layer in graphene/silicon solar cells

Abstract

The role of MoS₂ as an effective interfacial layer in graphene/silicon solar cells is systematically investigated by varying MoS₂ film annealing temperature and thickness. It is found that the power conversion efficiency (PCE) is increased by ∼100% from ∼2.3% to ∼4.4% with 80 °C annealed MoS₂ film whereas it drops significantly to ∼0.6% with 200 °C annealed MoS₂ film. The results are well explained based on the device energy band diagram. That is, the incorporation of MoS₂(80) films leads to the formation of type II structure, facilitating hole transport; while valence band mismatch is formed with MoS₂(200) films due to the increase in the work function of MoS₂. Besides, the PCE increases gradually with decreasing MoS₂ film thickness, and “saturates” at about 2 nm. The PCE can be further enhanced to ∼6.6% with the aid of silicon surface passivation. Our work demonstrates that MoS₂ is an excellent interfacial layer to improve the PCE with low-temperature annealing (80 °C in air), which may be helpful in developing efficient and low-cost G/Si solar cells.