A Concept of Bulk Electrophotovoltaic Effect

(By Xiao jiang, Lei Kang, Jianfeng Wang and Bing Huang)

Nonlinear light-matter interaction plays an important role in manipulating light and matter at the nanoscale. The shift current, as an important component of bulk photovoltaic effect (BPVE), is a unique second-order nonlinear optical process that can directly convert light into electricity. The BPVE holds great advantages in a series of modern physical applications, e.g., new generation of solar cells, ultra-sensitive optical detectors, and optically readable memristors and circuits. For all these applications, the key step is to realize giant and highly tunable shift current responses in real material systems. In the past, tremendous efforts have been made to achieve this goal, which is, however, largely unachieved. Therefore, a new physical concept is highly desired to solve this challenge.  

In the previous, Huang group developed the nonlinear optical calculations software (NOPSS [1,2]), which can be adopted to effectively calculate the many second-order nonlinear optical responses based on the wavefunctions from standard first-principles calculations or from tight-binding/kp modelling. Recently, they propose a fundamentally new concept named as bulk electrophotovoltaic effect (BEPVE), that is, an out-of-plane external electric-field can continuously tune in-plane shift current along with its sign flip in a hetero-nodal-line (HNL) system. Base on a two-band k.p model, they find an external electric-field can effectively control the radius of nodal-loop, which can continuously modulate the shift-vector components inside and outside nodal-loop holding opposite signs. To confirm this concept, they demonstrate the existence of giant BEPVE in the HNL system HSnN/MoS₂ using their NOPSS code. They discover that the HSnN/MoS₂ system can exhibit giant shift current ~3000 μA/V² around the band edge, at least 1~2 order of magnitude larger than any known BPVE materials. Most importantly, a small electric field enables a continuous current change from ~-6000 to ~6000 μA/V² along with the direction switch.  

This work has recently been published in Physical Review Letters [3] and selected as Editors’ Suggestion.  

References:

[1] X. Jiang, L. Kang, and B. Huang, Role of interlayer coupling in second harmonic generation in bilayer transition metal dichalcogenides, Phys. Rev. B, 105, 045415 (2022)

[2] X. Jiang, L. Ye, X. Wu, L. Kang, and B. Huang, Role of large Rashba spin-orbit coupling in second-order nonlinear optical effects of polar BiB₃O₆, Phys. Rev. B, 106, 195126 (2022).

[3] X. Jiang, L. Kang, J. Wang, B. Huang, Giant Bulk Electrophotovoltaic Effect in Hetero-nodal-line Systems, Phys. Rev. Lett., 130, 256902 (2023)

Figure: Schematic of bulk electrophotovoltaic effect.