Photovoltaic Effect and Evidence of Carrier Multiplication in Graphene Vertical Homojunctions with Asymmetrical Metal Contacts.
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.
State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University , Beijing 100871, P. R. China.
Jing-Jing
JJ
Chen
International Center for Quantum Materials, Peking University , Beijing 100871, P. R. China.
Qinsheng
Q
Wang
State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University , Beijing 100871, P. R. China.
Jie
J
Meng
EMAT (Electron Microscopy for Materials Science), University of Antwerp , Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
Xiaoxing
X
Ke
EMAT (Electron Microscopy for Materials Science), University of Antwerp , Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
Gustaaf
G
Van Tendeloo
State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University , Beijing 100871, P. R. China.
Ya-Qing
YQ
Bie
International Center for Quantum Materials, Peking University , Beijing 100871, P. R. China.|Qian Xuesen Laboratory of Space Technology, China Academy of Space Technology , Beijing 100094, P. R. China.
Junku
J
Liu
State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University , Beijing 100871, P. R. China.|Collaborative Innovation Center of Quantum Matter , Beijing 100084, P. R. China.
Kaihui
K
Liu
State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University , Beijing 100871, P. R. China.|Collaborative Innovation Center of Quantum Matter , Beijing 100084, P. R. China.
Zhi-Min
ZM
Liao
International Center for Quantum Materials, Peking University , Beijing 100871, P. R. China.|Collaborative Innovation Center of Quantum Matter , Beijing 100084, P. R. China.
Dong
D
Sun
State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University , Beijing 100871, P. R. China.|Collaborative Innovation Center of Quantum Matter , Beijing 100084, P. R. China.
Dapeng
D
Yu
carrier multiplication; graphene; photodetector; photovoltaics; vertical homojunction