Nickel Intercalation of Two-Dimensional SnS2 for Enhancing Optical Absorption and Tuning Ultrafast Photoexcited Carrier Dynamics

Two-dimensional (2D) SnS₂ is a layered semiconductor with a band gap in the visible range of spectrum (~ 2.3 eV) and high carrier mobility.^1,2 It has been put forth as a potential material for solar energy conversion.³ Here, we demonstrate that zerovalent intercalation of atomic Ni into the van der Waals gap of SnS₂ can change its optical and electronic properties, allowing absorption of light not only in the blue-green but over the entire visible spectrum. We also find that it significantly changes the lifetime of the charge carriers injected over the 2.3 eV gap. In the case of 400 nm excitation, we find that all optically injected carriers are trapped or recombine within 100 ps, while the lifetime of ~ 3x that is observed in pristine SnS₂. We hypothesize that Ni introduces a significant concentration of free carriers which enable broad spectrum absorption, while at the same time introducing additional trap states that limit the photoexcited carrier lifetime. Thus, Ni intercalation can thus be used to engineer the properties of SnS₂for its applications in solar energy conversion as well as for other optoelectronic and photonic applications.<br/><br/><br/><br/>(1) Huang, Y.; Sutter, E.; Sadowski, J. T.; Cotlet, M.; Monti, O. L. A.; Racke, D. A.; Neupane, M. R.; Wickramaratne, D.; Lake, R. K.; Parkinson, B. A.; et al. Tin disulfide—an emerging layered metal dichalcogenide semiconductor: materials properties and device characteristics. ACS Nano 2014, 8 (10), 10743-10755. DOI: 10.1021/nn504481r.<br/>(2) Kushnir Friedman, K.; Khanmohammadi, S.; Morissette, E. M.; Doiron, C. W.; Stoflet, R.; Koski, K. J.; Grimm, R. L.; Ramasubramaniam, A.; Titova, L. V. Ultrafast Shift Current in SnS2 Single Crystals: Structure Considerations, Modeling, and THz Emission Spectroscopy. Advanced Optical Materials n/a (n/a), 2400244. DOI: https://doi.org/10.1002/adom.202400244.<br/>(3) Giri, B.; Masroor, M.; Yan, T.; Kushnir, K.; Carl, A. D.; Doiron, C.; Zhang, H.; Zhao, Y.; McClelland, A.; Tompsett, G. A.; et al. Balancing light absorption and charge transport in vertical SnS2 nanoflake photoanodes with stepped layers and large intrinsic mobility. Advanced Energy Materials 2019, 9 (31). DOI: 10.1002/aenm.201901236.