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

Transition-metal dichalcogenide (TMD) nanotubes with small band gap exhibit higher photocurrent than their layered counterparts [J. H. Smet and Y. Iwasa, Nature (London) 570, 349 (2019); X. Zhou et al., Small 15, 1902528 (2019)], but the mechanism remains unclear. Herein, using WS2 as an example, we revealed that the higher photovoltaic effect of the nanotubes originates from the quantum coherence between the band edges in the perspective of photogenerated carrier recombination. By using first-principles calculations and nonadiabatic molecular dynamics simulations, we revealed that small nonadiabatic coupling and short pure-dephasing time improve the photogenerated carrier lifetime and increase the photocurrent of WS2 nanotubes. Moreover, an extremum of carrier lifetime in WS2 nanotubes is found at a certain diameter, where the nanotube exhibits the longest carrier lifetime. The insights into the high photocurrent of TMD nanotubes may provide ideas for the design of advanced optoelectronic devices.