The theoretical Shockley–Queisser limit of photon–electricity conversion in a conventional p–n junction could be potentially overcome by the bulk photovoltaic effect that uniquely occurs in non-centrosymmetric materials. Using strain-gradient engineering, the flexo-photovoltaic effect, that is, the strain-gradient-induced bulk photovoltaic effect, can be activated in centrosymmetric semiconductors, considerably expanding material choices for future sensing and energy applications. Here we report an experimental demonstration of the flexo-photovoltaic effect in an archetypal two-dimensional material, MoS2, by using a strain-gradient engineering approach based on the structural inhomogeneity and phase transition of a hybrid system consisting of MoS2 and VO2. The experimental bulk photovoltaic coefficient in MoS2 is orders of magnitude higher than that in most non-centrosymmetric materials. Our findings unveil the fundamental relation between the flexo-photovoltaic effect and a strain gradient in low-dimensional materials, which could potentially inspire the exploration of new optoelectronic phenomena in strain-gradient-engineered materials.
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This work is supported by the US Army Research Office under grant number W911NF-21-1-0013 (J.J. and J.S.) and Air Force Office of Scientific Research under grant number FA9550-18-1-0116 (Y.W. and J.S.). The work is also supported by the NYSTAR Focus Center at Rensselaer Polytechnic Institute with contract number C150117 (L.Z., Y.X., G.-C.W. and J.S.). This work is also partially supported by the National Science Foundation under award numbers 2024972, 2031692 and 1916652 (Y.H., Z.C. and J.S.).
The authors declare no competing interests.
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Jiang, J., Chen, Z., Hu, Y. et al. Flexo-photovoltaic effect in MoS2. Nat. Nanotechnol. 16, 894–901 (2021). https://doi.org/10.1038/s41565-021-00919-y
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