Ultrafast photoconductivity and terahertz vibrational dynamics in double-helix SnIP nanowires

TL;DR

This study investigates the ultrafast photoconductivity and vibrational dynamics of SnIP nanowires, revealing high electron mobility and charge redistribution mechanisms crucial for optoelectronic applications.

Contribution

It provides the first detailed measurement of transient photoconductivity and vibrational responses in SnIP nanowires, highlighting their high mobility and charge dynamics.

Findings

Electron mobility up to 280 cm^2V^{-1}s^{-1}

Charge redistribution reduces twisting mode amplitude

Carrier lifetime limited by high trap density

Abstract

Tin 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, our understanding of the fundamental photophysics and charge transport dynamics of this new material is limited. Here, we use time-resolved terahertz (THz) spectroscopy to probe the transient photoconductivity of SnIP nanowire films and, with insight into the highly anisotropic electronic structure from quantum chemical calculations, measure an electron mobility as high as 280 $cm^2V^{-1}s^{-1}$. Additionally, the THz vibrational spectrum reveals a photoexcitation-induced charge redistribution that reduces the amplitude of a twisting mode of the outer SnI helix on picosecond timescales. Finally, we show that the carrier lifetime and mobility are limited by a trap density greater than $10^{18}\,cm^{-3}$. Our 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.