Back contact modification of the optoelectronic device with transition metal dichalcogenide VSe₂ film drives solar cell efficiency

VSe₂ is with high electrical conductivity and high work function, thus it is beneficial for the carrier transport in the optoelectronic devices. However, the performance and mechanism of its effect on the photoelectronic devices conversion efficiency is still beyond understood. In this work, we fabricate VSe₂ film between back contact and absorber layer Cu₂ZnSn(S,Se)₄ (CZTSSe) film. We demonstrate that the VSe₂ film in back contact region increases solar cell efficiency by 39%. Besides improving the carrier transport in the back contact region, the increasing can also be attributed to the reduction of the decomposition reaction of CZTSSe during the nucleation of CZTSSe as VSe₂ fabricated between back contact and absorber layer. The present work not only provides an effective method to improve the performance of the optoelectronic device, but also shows an attractive application of metallic TMDs in optoelectronic device and solar cell energy generation.