Enhanced near-infrared photoresponse of SnS2 nanosheets by Er–Yb co-doping

Rare earth (RE) ions are important dopants to modulate semiconductor properties because of their abundant energy levels. Herein, a simple Er–Yb co-doping strategy was developed to enhance the near-infrared optoelectronic properties of SnS2 nanosheets. The constructed device based on Er–Yb co-doping SnS2 has a detectivity of ∼4.97 × 108 Jones at 980 nm. The enhanced photoresponse of the doped system at 980 nm could be attributed to the upconversion behavior of the Er–Yb ion pairs. The Yb3+ ions as sensitizers significantly enhance the upconversion emission and near-infrared photoresponse properties of the material. The energy transfer from Yb3+ to Er3+ ions can occur between different layers of co-doping nanosheets by investigating the properties of the constructed SnS2:Er/SnS2:Yb homojunction nanosheets. Density functional theory calculations reveal that Er or Yb doping introduces slight structural and charge distribution changes owing to the similarity in the metal–atom coordination structure between SnS2 and RE sulfide. Our study demonstrates that RE doping is an effective way to improve the near-infrared photoresponse of 2D materials and clarifies the relationship between luminescence and photoelectric properties.