Bulk Photovoltaic Effect in Two-Dimensional Distorted MoTe₂

Abstract

In future solar cell technologies, the thermodynamic Shockley-Queisser limit for solar-to-current conversion in traditional p−n junctions could potentially be overcome with a bulk photovoltaic effect by creating an inversion broken symmetry in piezoelectric or ferroelectric materials. Here, we unveiled mechanical distortioninduced bulk photovoltaic behavior in a two-dimensional (2D) material, MoTe 2 , caused by the phase transition and broken inversion symmetry in MoTe 2 . The phase transition from single-crystalline semiconducting 2H-MoTe 2 to semimetallic 1T′-MoTe 2 was confirmed using X-ray photoelectron spectroscopy (XPS). We used a micrometerscale system to measure the absorption of energy, which reduced from 800 to 63 meV during phase transformation from hexagonal to distorted octahedral and revealed a smaller bandgap semimetallic behavior. Experimentally, a large bulk photovoltaic response is anticipated with the maximum photovoltage V OC = 16 mV and a positive signal of the I SC = 60 μA (400 nm, 90.4 Wcm −2 ) in the absence of an external electric field. The maximum values of both R and EQE were found to be 98 mAW −1 and 30%, respectively. Our findings are distinctive features of the photocurrent responses caused by in-plane polarity and its potential from a wide pool of established TMD-based nanomaterials and a cutting-edge approach to optimize the efficiency in converting photons-to-electricity for power harvesting optoelectronics devices.

Room-Temperature Geometrical Circular Photocurrent in Few-Layer MoS2

“…Such a symmetry breaking can manifest in the CPC dependence on the orientation of the electrode–sample interface with respect to the crystal geometry, i.e., a geometrical CPC . Recent findings, as demonstrated by research on MoTe 2 , reveal that mechanical distortion-induced bulk photovoltaic behavior in piezoelectric or ferroelectric materials offers a pathway to surpass the traditional solar-to-current conversion limits. Moreover, the interface can also result in the localized Schottky barrier, contributing to increased exciton dissociation and electrically tunable CPC …”

Progress in photodetector devices utilizing transition metal dichalcogenides

“…1–6 The developed PD technologies have so far covered a wide range of applications that have a significant impact on our daily lives such as visible light detection for video imaging and digital cameras, ultraviolet (UV) radiation for cell inspection and lithography, X-ray radiation for biomedical imaging, wide-range infrared (IR) detection for night vision, environmental monitoring, optical communication, and quality testing spectroscopy, among others. 7–20 PDs are categorized using several key figures-of-merit such as photogain, quantum efficiency, detectivity, responsivity and others. The related terminologies and characteristics for the PDs are summarized in Fig.…”

Strain-Prompted Giant Flexo-Photovoltaic Effect in Two-Dimensional Violet Phosphorene Nanosheets

“…Photovoltaic devices employing the conventional p–n structure have nearly reached the Shockley–Queisser limit in terms of photoelectric conversion efficiency. , Conversely, the bulk photovoltaic (BPV) effect, stemming from the accumulation of photocurrent induced by uniform illumination in noncentrosymmetric materials, is not constrained by this limitation and regarded with high expectations. − This second-order nonlinear optical effect was commonly observed in a series of piezoelectric and ferroelectric materials such as BaTiO 3 (BTO), Pb­(Zr x Ti 1– x )­O 3 (PZT), and Bi 2 FeCrO 6 (BFCO), while recently has been discovered to exist in two-dimensional materials. ,,− , …”

“…Through strain engineering, the flexo-photovoltaic (FPV) effect, a form of BPV effect, can be artificially generated by manipulating the spatial inversion symmetry of the system. − , Strain induces crystal point group degeneracy in two-dimensional materials, resulting in nonzero independent matrix elements in the BPV tensor, which contributes to the photocurrent in the system. This approach has been successfully implemented in various 2D materials.…”