Highly Crystalline Nanoflakes WS2 Heterojunction Photovoltaics for Solar Energy Harvesting

Graduate #76
Discipline: Nanoscience
Subcategory: Nanoscience

Kelsea Yarbrough - Norfolk State University
Co-Author(s): Ruth Holden, Norfolk State University, Norfolk,VA; Sangram K. Pradhan, Norfolk State University, Norfolk,Va; Messaoud J. Bahoura, Norfolk State University, Norfolk,Va

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In the past few years, two-dimensional transition metal dichalcogenides has gained noteworthy attention due to their unique electrical, optical, and structural properties. Traditional photovoltaic (PV) solar energy conversion devices based on established inorganic semiconductors may not be able to meet the renewable energy production targets needed to mitigate climate change in the next 30-40 years. Among the 2D materials WS2 is a promising materials having tunable bandgap that can be manipulated from indirect bandgap to direct bandgap by controlling the thickness of the WS2 layers and can be easily grown in every substrate. This tunable bandgap provides a suitable platform for the fabrication of several devices including, solar cells, transistors, photodetectors, and electroluminescent devices. High quality conformal WS2 films were grown by radio frequency sputtering on p- type silicon substrate at different substrate temperature to fabricate a hetero PN junction device. XRD image shows that the WS2 layers are highly single crystalline in nature. FESEM images show an interesting image of changing the surface morphology from thin films to nano-structure/flakes by increasing the deposition time of WS2 layers. The films are highly conducting in nature and showing photo response behavior by the irradiation of electromagnetic wave. I-V measurement shows the ideal PN junction characteristic of the device and photo current are observed by exposing visible spectrum of light. The present work will provide valuable scientific input of layered WS2 films for other emerging applications

ERN Abstract_Yarbrough.docx

Funder Acknowledgement(s): NSF-CREST Grant number HRD 1547771 NSF-CREST Grant number HRD 1036494

Faculty Advisor: Sangram Pradhan, skpradhan@nsu.edu

Role: I have performed all of the optimization of the grown WS2 films, as well as the characterization for some of the results. The XRD results were performed by my advisor/mentor.