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WS2-Induced Enhanced Optical Absorption and Efficiency in Graphene/Silicon Heterojunction Photovoltaic Cells


The Van Hove singularity (VHS) induced enhancement of visible-frequency-absorption in atomically-thin two-dimensional (2D) crystals provides an opportunity for improved light management in photovoltaics; however, it requires the 2D nanomaterial to be in close vicinity to a photojunction. In this report, we design a Schottky junction-based photovoltaic system with single-layer graphene atop n-type silicon (n-Si), which is interfaced directly with few-layers of tungsten disulfide (WS2) via a bottom-up CVD synthesis strategy. An enhanced power conversion efficiency in the architecture of WS2-graphene/n-Si is observed compared to graphene/n-Si. Here, the WS2 induced photon absorption, only one atom above the photo-junction enhanced short-circuit current density (JSC), and the reconfiguration of the energy band structure led effective built-in electric field induced charge carrier transport (enhanced open-circuit voltage (VOC)). Similar to graphene/n-Si Schottky junction, the WS2-graphene/n-Si double junction exhibited non-linear current density-voltage (J-V) characteristics with a 4-fold increase in JSC (2.28 mA/cm2 in comparison to 0.52 mA/cm2 for graphene/n-Si) and 40% increase in the VOC (184 mV compared to 130 mV for graphene/n-Si) with a 6-fold increase in the photovoltaic power conversion efficiency. Futuristically, we envision an evolution in 2D heterojunctions with sharp-transitions in properties within a few nanometers enabling control on optical-absorption, carrier-distribution, and band-structure for applications including tandem photovoltaic cells and 2D optoelectronic circuit-switches.

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Publication details

The article was received on 19 Apr 2018, accepted on 30 Sep 2018 and first published on 01 Oct 2018

Article type: Paper
DOI: 10.1039/C8NR03194K
Citation: Nanoscale, 2018, Accepted Manuscript
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    WS2-Induced Enhanced Optical Absorption and Efficiency in Graphene/Silicon Heterojunction Photovoltaic Cells

    R. Debbarma, S. Behura, Y. Wen, S. Che and V. Berry, Nanoscale, 2018, Accepted Manuscript , DOI: 10.1039/C8NR03194K

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