Van Der Waals Semiconductor Based Omnidirectional Bifacial Transparent Photovoltaic for Visual-Speech Photocommunication

Abstract

Omnidirectional photosensing is crucial in optoelectronic devices, enabling a wide field of view (wFoV) and leveraging potential applications for the Internet of Things in sensors, light fidelity, and photocommunication. The wFoV helps overcome the limitations of line-of-sight communication, and transparent photodetection becomes highly desirable as it enables the capture of optical information from various angles. Therefore, developing a photoelectric device with a 360° wFoV, ultra sensitivity to photons, power generation, and transparency is of utmost importance. This study utilizes a heterojunction of van der Waals SnS with Ga₂ O₃ to fabricate a transparent photovoltaic (TPV) device showing a 360° wFoV with bifacial onsite power production. SnS/Ga₂ O₃ heterojunction preparation consists of magnetron sputtering and is free from nanopatterning/nanostructuring to achieve the desired wFoV window device. The device exhibits a high average visible transmittance of 56%, generates identical power from bifacial illumination, and broadband fast photoresponse. Careful analysis of the device shows an ultra-sensitive photoinduced defect-modulated heterojunction and photocapacitance, revealed by the impedance spectroscopy, suggesting photon-flux driven charge diffusion. Leveraging the wFoV operation, the TPV embedded visual and speech photocommunication prototype demonstrated, aiming to help visually and auditory impaired individuals, promising an environmental-friendly sustainable future.

Keywords: field of view; omnidirectional; photocommunication; transparent photovoltaics; van der Waals.

Figure 1

a) Structural transition of SnS₂ phase to SnS phase under the PVD technique at 300 °C deposition temperature. b) XRD spectra of the Ga₂O₃ and SnS film grown on the glass substrate. c) Optical characteristics (transmittance and absorbance) of the SnS, Ga₂O₃, and Ga₂O₃/SnS heterojunction. d) High‐resolution TEM cross‐sectional image of the Ga₂O₃/SnS TPV. e) Elemental phase mapping of combined and individual Ga, O, Sn, S, and Ag elements obtained at the cross‐section. f) The interfacial TEM image depicts the interface formation between Ga₂O₃ and SnS. Zoomed‐in TEM micrograph of the SnS. XPS spectra of Ga₂O₃ film for g) Ga2P and h) O1s core level. XPS spectra of SnS film for g) Sn3d and h) S2p core level.

Figure 2

a) Schematic diagram of the TPV under light illumination. b) Transmittance and the photopic response of the complete TPV (AgNWs/SnS/Ga₂O₃/FTO). Inset: an image of the TPV. c) Semilogarithmic and linear I‐V curves under dark and illumination conditions. d) Linear J–V curve of the device demonstrating bifacial nature under illumination from bottom and top. e) Power density curve of the TPV device for the bottom and top illumination. f) Angle‐dependent linear J–V characteristics of the TPV device under UV light (365 nm) illumination with an intensity of 10 mW cm⁻². g) Transient photocurrent response of the TPV under illumination from the UV (340 nm) to NIR (850 nm) exhibiting broadband photoresponse.

Figure 3

a) Polar coordinates represent the movement of the light source along the X, Y, and Z axes. b) Photocurrent response at ɸ = 0^o with the variation of θ from 0 to 180^o. Morse code photoresponse deciphering c) SOS and d) TPV with a light source at θ= 0^o and ɸ = 0^o. e) Photocurrent response of the device under the movement of the light source at ɸ = 0^o with the variation of θ from 0 to 360^o. f) Contour plot of the device for photocurrent under the variation of θ and ɸ from 0^o to 180^o.

Figure 4

a) Mott–Schottky (1/C²‐V) curve and b) aerial capacitance versus voltage characteristics of the device under dark and different illumination conditions. c) Flat band and capacitance behavior to the illumination photon flux. d) Energy band alignments of different interfaces (FTO‐Ga₂O₃, Ga₂O₃‐SnS, SnS‐AgNW) under dark and illumination conditions. Photon‐induced charge injection under illumination. e) Equivalent circuits for dark, low‐injection, and high‐injection conditions. f) Cole–Cole plot and g) Bode amplitude and bode phase plot under dark and illumination conditions.

Figure 5

a) Depiction of the concept behind the proposed device. b) Schematic diagram of the module developed for visual and speech PC, c) Visual‐speech PC module. d) Visual‐speech PC module to record the omnidirectional behavior of the TPV.