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Flexo-photovoltaic effect in MoS2

Abstract

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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Fig. 1: Microscopic views of the BPV and flexoelectric effects.
Fig. 2: FPV effect of the MoS2 sheet at room temperature.
Fig. 3: Temperature-dependent FPV effect of the MoS2 sheet.
Fig. 4: Overview of the BPV effect in non-centrosymmetric materials.

Data availability

The data of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

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.).

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J.J. and J.S. conceived the idea and designed the experiments (device structure, temperature-dependent and photon-polarization-dependent measurements). J.J. built the 2D materials transfer system and assembled the SPCM setup. J.J. prepared samples and fabricated the devices. Y.W. assisted with the growth of VO2. J.J. performed Raman mappings, photocurrent mappings and light polarization dependence measurements. Z.C. and Y.H. assisted photocurrent measurements and calibrations. Y.X. and L.Z. performed atomic force microscopy measurements. J.J. processed the data. J.J. and J.S. analysed and interpreted the results. J.J. wrote the paper. All the authors were involved in the discussion for data analysis. G.-C.W. and J.S. revised the manuscript. J.S. supervised the project.

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Correspondence to Jie Jiang or Jian Shi.

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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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