Controllable Photoelectric Properties in Double-Wall MoS2 Nanotubes by the Flexoelectric Effect

Transition-metal dichalcogenide (TMD) nanotubes can be used as promising candidates for constructing high-efficiency solar cells without the need for p-n junctions. However, the role of spontaneous flexoelectricity in TMD nanotubes on photoelectric properties remains unclear. Here, we propose a theoretical model to investigate the influence of a spontaneous flexoelectric effect on the collection efficiency of carriers and power conversion efficiency (PCE) of double-wall MoS2 nanotubes based on the atomic-bond-relaxation theory and the detailed balance principle. We find that as the diameter increases, the flexoelectricity in double-wall MoS2 nanotubes can lead to a band alignment transition from type I to type II, and the critical diameter is 3.1 nm. Especially, the optimal PCE of double-wall MoS2 nanotubes can reach up to 5.25% at a fixed diameter of 5.2 nm. Our results show that the optimal PCE of double-wall MoS2 nanotubes is 7 times larger than that of bilayer MoS2, suggesting that the flexoelectricity can be adopted as an effective way to develop new types of photovoltaic devices.