Photovoltaic Effect and Evidence of Carrier Multiplication in Graphene Vertical Homojunctions with Asymmetrical Metal Contacts

• Published in: ACS nano Vol. 9; no. 9; pp. 8851 - 8858
• Main Authors: Chen, Jing-Jing, Wang, Qinsheng, Meng, Jie, Ke, Xiaoxing, Tendeloo, Gustaaf Van, Bie, Ya-Qing, Liu, Junku, Liu, Kaihui, Liao, Zhi-Min, Sun, Dong, Yu, Dapeng
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 22.09.2015
• Subjects: Carriers; Devices; Graphene; Homojunctions; Multiplication; Photovoltaic cells; Quantum efficiency; Solar cells; carrier multiplication; graphene; photodetector; photovoltaics; vertical homojunction
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/acsnano.5b02356

Graphene exhibits exciting potentials for high-speed wideband photodetection and high quantum efficiency solar energy harvest because of its broad spectral absorption, fast photoelectric response, and potential carrier multiplication. Although photocurrent can be generated near a metal–graphene interface in lateral devices, the photoactive area is usually limited to a tiny one-dimensional line-like interface region. Here, we report photoelectric devices based on vertical graphene two-dimensional homojunction, which is fabricated via vertically stacking four graphene monolayers with asymmetric metal contacts. The devices show excellent photovoltaic output with excitation wavelength ranging from visible light to mid-infrared. The wavelength dependence of the internal quantum efficiency gives direct evidence of the carrier multiplication effect in graphene. The simple fabrication process, easy scale-up, large photoresponsive active area, and broadband response of the vertical graphene device are very promising for practical applications in optoelectronics and photovoltaics.