Flexoelectricity-Enhanced Self-Powered Photodetection in 2D van der Waals Heterojunctions With Large Curvatures

The unique morphology of 2D van der Waals materials enables them to withstand large deformations and significant nonuniform strain, potentially inducing a strong flexoelectric effect. Despite the size-dependent flexoelectric effect showing potential for modulating the optoelectronic performance of 2D van der Waals materials, it is far from being fully exploited owing to various challenges. Herein, the use of nanowires with different diameters as the bending media to fabricate 2D alpha-In2Se3/beta-InSe heterojunctions with large curvatures of 0.1-1 mu m-1 is proposed. The significant band alignment modulation in alpha-In2Se3 resulting from the bending-induced flexoelectric effect is verified through Kelvin probe force microscopy. The strain-induced piezoelectric effect can be negated because of the weak vdW forces at the interface. The flexoelectric polarization in beta-InSe is screened via the accumulated electrons in the unilateral depleted heterojunction. Compared to the flat heterojunction, the curved heterojunction with an average curvature of 0.9 mu m-1 shows 2.48-fold and 7.62-fold increases in open-circuit voltage and zero-biased responsivity, respectively. This study demonstrates the first successful modulation of photodetection in 2D heterojunctions by exploiting the flexoelectric effect, providing a new perspective for high-performance 2D vdW optoelectronic devices. The use of nanowires with different diameters as the bending media to fabricate 2D alpha-In2Se3/beta-InSe heterojunctions with large curvatures as high as 1 x 106 m-1 is proposed. This strategy allows us to demonstrate the first successful modulation of self-powered photodetection in 2D heterojunctions via a strong flexoelectric effect. image