Carrier Dynamics and Ultrafast Zero-Bias Photocurrents in SnS₂ Single Crystals

Moderate band gaps, high carrier mobility, and environmental stability make layered transition metal dichalcogenides attractive for optoelectronic and solar energy conversion applications. Of these materials, SnS₂ demonstrates promise as a photocatalyst for visible light water splitting and in field-effect devices, with reported on-off current ratios >10⁶ and carrier mobilities up to 230 cm² V^–1 s^–1 [1,2]. Further progress in application of this emergent material requires the understanding of the dynamics of photoinjected carriers and optical excitations.

We present the synthesis of single-crystal SnS₂ and its subsequent characterization by terahertz (THz) spectroscopy of carrier dynamics with sub-picosecond time resolution. Emission spectroscopy of photoinduced ultrafast currents probe the presence of shift currents, or zero-bias photocurrents, that appear to be a function of crystal orientation. The observation herein of zero-bias photocurrents indicates the viability of SnS₂ nanosheets for third generation shift current photovoltaics.

[1] Huang et. al., ACS Nano 8, 10743 (2014)
[2] Sun et al., Angew. Chem., Int. Ed. 51, 8727–8731 (2012)