Ultra-fast and high flexibility near-infrared photodetectors based on Bi2Se3 nanobelts grown via catalyst-free van der Waals epitaxy

van der Waals epitaxy (vdWe) method has recently attracted considerable interest due to its extensive application in the growth of layered structure materials. However, the growth process of vdWe is not completely understood. Here, we report the controlled growth process of Bi2Se3 nanobelts and study their photoresponse behaviour. The average length of nanobelts increases from 7 μm to 17 μm by adjusting the temperature of Bi2Se3 powder from 520 °C to 530 °C, however the average length becomes saturated with further increasing the source material temperature over 530 °C. Such a change can be attributed to the competition between the process of Bi2Se3 molecule diffusion and the process of crystal formation-related chemical reaction, leading to a symmetrically studying for the growth process of catalyst-free vdWe growth of Bi2Se3 nanobelts. The photodetectors based on these Bi2Se3 nanobelts show excellent device performance in the near-infrared light range, including an ultra-fast photoresponse (trsing ≈ 37 ms, tdecay ≈ 62 ms), a high responsivity of 10.1 mA/W and a high detectivity of 4.63 × 108 Jones. This high device performance could be related to the excellent carrier transport properties as Bi2Se3 nanobelt photodetectors also demonstrate a great potential for fabricating flexible and wearable electronics by still showing stable photoresponse after bending the device for 200 times. •We demonstrate a controlled catalyst-free vdWe process of Bi2Se3 nanobelts.•A high-performance flexible NIR photodetector based on Bi2Se3 nanobelts is measured and analyzed for the first time.•The NIR photodetector shows ultra-fast photoresponse (tr ≈ 37 ms, td ≈ 62 ms), a high responsivity and detectivity