  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
material (2D), MoTe2, caused by phase transition and broken inversion symmetry
in MoTe2. The phase transition from single-crystalline semiconducting 2H-MoTe2
to semi-metallic 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 meV to 63 meV when phase transformation from hexagonal
to distorted octahedral and revealed a smaller bandgap semi-metallic behavior.
Experimentally, a large bulk photovoltaic response is anticipated with the
maximum photovoltage VOC = 16 mV and a positive signal of the ISC = 60 uA (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 unveil 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 novel approach to reach high efficiency in converting
photons-to-electricity for power harvesting optoelectronics devices.
