Free-standing [0 0 1]-oriented one-dimensional crystal-structured antimony selenide films for self-powered flexible near-infrared photodetectors

Flexible optoelectronic is one of the key components for acquiring biological signals in wearable devices and implantable systems. Recently, antimony selenide (Sb2Se3) has shown an exciting potential for flexible optoelectronic applications due to its unique one-dimensional (1D) ribbon-typed crystal structure, low-cost constituents, and superior optoelectronic properties. However, the growth of [0 0 1]-oriented Sb2Se3 film, which can efficiently enhance the carrier transport, is still challenging, particularly for its application in flexible electronics. Herein, we propose to grow the free-standing [0 0 1]-oriented Sb2Se3 film for self-powered flexible photodiode through selenizing the highly (0001)-textured Sb film on mica substrate. The theoretical calculation reveals that Sb(0001) plane provides a high adsorption energy for Se atoms, which promotes the [0 0 1]-oriented growth of Sb2Se3 film. The weak vdW interaction between Sb2Se3 film and mica substrate enables the film separation, and results in a free-standing Sb2Se3 film. Benefiting from the enhanced carrier transport in [0 0 1]-oriented Sb2Se3 film, the flexible photodiode exhibits a high responsivity up to 0.74 A W−1, a specific detectivity of 5.1 × 1013 Jones, a linear dynamic range of 102 dB, rise/fall time of 0.16/0.15 ms for near-infrared light detection without any external bias, and excellent folding endurance after 1000 bending cycles. It has been also successfully employed as a wearable photodetector to detect a person's heart rate. This work demonstrates a strategy for the orientation control of low-dimensional crystal-structured materials and a great potential of free-standing films in flexible electronics applications.