Ultrafast Photoconductivity and Terahertz Vibrational Dynamics in Double‐Helix SnIP Nanowires

• DOI: 10.1002/adma.202100978
• Publication Date: 2021-07-19T07:20:56Z
• Authors: David N. Purschke; Markus R. P. Piel...; Ebru Üzer; Claudia Ott; Charles Jensen; Annabelle Degg; Anna Vogel; Naaman Amer; Tom Nilges; Frank A. Hegmann
• Keywords: Condensed Matter - Materials Science; Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences; 02 engineering and technology; 0210 nano-technology; 7. Clean energy

AbstractTin iodide phosphide (SnIP), an inorganic double‐helix material, is a quasi‐1D van der Waals semiconductor that shows promise in photocatalysis and flexible electronics. However, the understanding of the fundamental photophysics and charge transport dynamics of this new material is limited. Here, time‐resolved terahertz (THz) spectroscopy is used to probe the transient photoconductivity of SnIP nanowire films and measure the carrier mobility. With insight into the highly anisotropic electronic structure from quantum chemical calculations, an electron mobility as high as 280 cm2 V−1s−1 along the double‐helix axis and a hole mobility of 238 cm2 V−1 s−1 perpendicular to the double‐helix axis are detected. Additionally, infrared‐active (IR‐active) THz vibrational modes are measured, which shows excellent agreement with first‐principles calculations, and an ultrafast photoexcitation‐induced charge redistribution is observed that reduces the amplitude of a twisting mode of the outer SnI helix on picosecond timescales. Finally, it is shown that the carrier lifetime and mobility are limited by a trap density greater than 1018 cm−3. The results provide insight into the optical excitation and relaxation pathways of SnIP and demonstrate a remarkably high carrier mobility for such a soft and flexible material, suggesting that it could be ideally suited for flexible electronics applications.