Transition metal dichalcogenide (TMD) nanotubes with small band gap exhibit higher photocurrent than its layered counterparts, but the mechanics remains unclear. Herein, by combining first-principles calculations and nonadiabatic molecular dynamics simulations and taking tungsten disulfide (WS2) as an example, we reveal from the perspective of photo-generated carrier recombination that the anomaly originates from the quantum coherence induced by structural effect. Specifically, the broken symmetry of WS2 nanotubes fastens the pure-dephasing time and prolongs the carrier lifetime, which ultimately leads to substantial increase of the photocurrent. Moreover, our results show WS2 nanotube with 5 nm diameter exposes the longest carrier lifetime (12 ns), ~ 25 times longer than that of WS2 monolayer. The in-depth insights into the high photocurrent of TMD nanotubes unraveled here may provide new ideas for the design of advanced optoelectronic devices.

Quantum coherence enhanced carrier lifetime of WS2 nanotubes: A time-domain ab initio study

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