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Hybrid perovskite possesses excellent photoelectric properties, including large light-absorption capacity and high carrier mobility, and is an ideal light-absorbing material for photoelectric devices. The grain size and compactness of hybrid perovskite are key factors affecting the performance of photoelectric devices. The photocurrent and photoresponsivity of these devices are relatively low because of the rapidly recombined photoexcited electron-hole pairs in hybrid perovskite. Herein, we develop a facile two-step chemical vapor deposition (CVD) method to synthesize a high-quality van der Waals (vdWs) MAPbI3/graphene heterostructure for high-performance image sensor. We introduced inorganic sources (PbI2) to vdWs epitaxially grown PbI2 film on a seamless graphene monolayer film template through CVD. Methylammonium iodide (MAI) was then reintroduced to prepare the vdWs MAPbI3/graphene heterostructure. The MAPbI3 layer is composed of densely packed, large-size grains and displays a smooth surface. High photoresponsivity of 107 A/W is achieved in the corresponding photodetector. Inspired by the human visual system, we designed a flexible photodetector array containing (24 × 24) pixels, achieving perfect image recognition and color discrimination. Our study may greatly facilitate the construction of high-performance optoelectronic devices in artificial retina, biomedical imaging, remote sensing, and optical communication.

Summary Electronic textile (E-textile) has drawn tremendous attention with the development of flexible and wearable electronics in recent years. Herein, we report the direct printing of E-textile composed of core-sheath fibers by employing a 3D printer equipped with a coaxial spinneret. Customer-designed core-sheath fiber-based patterns can be printed on textile for various purposes. For demonstration, we used carbon nanotubes (CNTs) as a conductive core and silk fibroin (SF) as a dielectric sheath, and fabricated a CNTs@SF core-sheath fiber-based smart pattern, which was further used as a triboelectricity nanogenerator textile. The smart textile could harvest biomechanical energy from human motion and achieve a power density as high as 18 mW/m2. We also demonstrated the printing of a supercapacitor textile for energy storage. The direct printing of smart patterns on textile may contribute to the large-scale production of self-sustainable E-textile with integrated electronics.

Graphene layers grown on metallic substrates by chemical vapor deposition generally exhibit wrinkles due to mismatches in thermal expansion coefficients of the graphene and the substrates, which affect remarkably the tribological, mechanical and electrical properties of graphene-based devices. Here we report an isotropic-stretching method to eliminate these wrinkles. The morphology evolution of the wrinkles during the stretching process is studied using an atomic force microscope, and a simple method for calculating the critical strain required to eliminate the wrinkles is suggested. Friction and scratching tests demonstrate that for graphene layers the friction and anti-wear performances of regions with eliminated pre-existing wrinkles are as good as the wrinkle-free regions. Our method is expected to be applicable to other layered materials grown on deformable surfaces.