A monolayer MoS ₂ p-n homogenous photodiode with enhanced photoresponse by piezo-phototronic effect

Transition-metal dichalcogenides (TMDCs) have recently open a new perspective in electronics and optoelectronics due to their unique planar crystal structures and incredible physical characteristics. Strong in-plane piezoelectricity is their unique property owing to non-centrosymmetric structure, differing from other two dimension (2D) materials, such as graphene and black phosphorus. In this work, we develop a flexible photodiode based on monolayer MoS2 lateral p-n homojunction with significant enhancement in photoresponsivity and detectivity. Piezo-phototronic effect is used to achieve this enhancement by adjusting the barrier height and broadening depletion zone at p-n junction interface under external strain. The wider depletion zone benefits the separation and transport of photogenerated carriers, thus enhancing the photocurrent. When a 0.51% external static tensile strain was applied, the photoresponsivity and detectivity are improved up to 1162 A W−1 and 1.72 × 1012 Jones, with about 619% and 319% enhancement compared with strain-free state, respectively. Consequently, this work provides an effective strategy to utilize unavoidable external strain to improve TMDCs-based optoelectronic devices performance. At the same time, it has reference meaning to achieve flexible, low-consumption and high-performance 2D devices without electric gate-control.