The effect of MoS2 modulated doping with molybdenum-oxide on the photovoltaic performance for MoS2/n-Si heterojunction solar cells

Achieving large Fermi energy splitting under illumination is critical for improving the performance of photovoltaic devices. In this work, we conducted the energy band structure modulation of MoS 2 thin films via MoO x doping scheme to realize its photovoltaic operation on n-type c-Si by magnetron sputtering. It is found that, by capping a MoO x overlayer, the MoS 2 electrons density decreased and the Fermi level shifted ~0.4 eV towards valence band, consequently the MoS 2 conductive type changing. With this doped MoS 2 layer, the built-in electric field of fabricated MoS 2 /n-Si heterojunction devices greatly improved and exceeded 400 mV owing to the larger interface energy-level differences. Meanwhile, the defects recombination losses reduced benefiting from the holes-selective behavior of O-deficiencies in MoO x , so that the photo-generated carriers extraction process were promoted. As a result, the doped MoS 2 /n-Si devices showed excellent rectification behavior with rectifying ratio to 10 5 and ideality of 1.12. The TRPL spectrums corroborated the enhanced carrier transport mechanism at MoS 2 /n-Si interface by MoO x modulation doping effect. Correspondingly, the significant improvement of doped MoS 2 /n-Si solar cells performance (V oc of 289 mV, FF of 60.72% and J sc of 31.25 mA/cm 2 ) was achieved, exhibiting an optimized conversion efficiency of 5.47%. The UPS analysis revealed that the doping mechanism of MoO x /MoS 2 stacks lies in energy band overlap and electrons contact transfer between these two materials. This observation of MoO x modulation doping effect on large-area sputtering MoS 2 could help in building a better interface carrier transport in photovoltaic and optoelectronic applications of 2D materials.