Bulk Photovoltaic Effect in Two-Dimensional Distorted MoTe₂

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 distortion-induced bulk photovoltaic behavior in a two-dimensional (2D) material, MoTe₂, caused by the phase transition and broken inversion symmetry in MoTe₂. The phase transition from single-crystalline semiconducting 2H-MoTe₂ to semimetallic 1T'-MoTe₂ was confirmed using X-ray photoelectron spectroscopy (XPS). We used a micrometer-scale 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.