Performance Enhancement of Highly Flexible SnS(p)/MoS2(n) Heterostructure based Broadband Photodetector by Piezo-phototronic Effect

Abstract

The work demonstrates the fabrication of a flexible p-SnS/n-MoS2 heterostructure based piezo-phototronic photodetector and understanding the detailed charge transport mechanism. Electrical measurement of fabricated heterojunction shows excellent rectification behavior with an ideality factor of ∼ 2.06. When the external strain is applied on the device, due to non-centrosymmetric structure of MoS2, piezo-potential gets induced in MoS2, which modulates the band structure and increases the width of the depletion region across the junction. The increase in depletion region results in a strong built-in electric field, which promotes the separation of photogenerated electron-hole (e-h) pairs more effectively and improves photogenerated charge carrier transport across the p-SnS/n-MoS2 interface. The photoresponsivity of the device is increased by ∼ 97 % at ∼ 2% tensile strain by piezo-phototronic effect compared to strain-free conditions. Energy band structure drawn by the values extracted from real-time ultraviolet photoelectron spectroscopy (UPS) measurements are used to explain the physical working mechanism behind the enhancement of photoresponsivity. The fabricated SnS/MoS2 heterostructure showed a higher photoresponsivity in visible region compared to NIR region due to higher absorption in the visible region. This work demonstrates the cost-effective approach for the development high performance photodetectors by using piezotronic interface engineering and paves the way for future flexible and wearable optoelectronics.