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Published August 2014 | Supplemental Material
Journal Article Open

Performance Enhancement of a Graphene-Zinc Phosphide Solar Cell Using the Electric Field-Effect


The optical transparency and high electron mobility of graphene make it an attractive material for photovoltaics. We present a field-effect solar cell using graphene to form a tunable junction barrier with an Earth-abundant and low cost zinc phosphide (Zn_3P_2) thin-film light absorber. Adding a semitransparent top electrostatic gate allows for tuning of the graphene Fermi level and hence the energy barrier at the graphene-Zn_3P_2 junction, going from an ohmic contact at negative gate voltages to a rectifying barrier at positive gate voltages. We perform current and capacitance measurements at different gate voltages in order to demonstrate the control of the energy barrier and depletion width in the zinc phosphide. Our photovoltaic measurements show that the efficiency conversion is increased 2-fold when we increase the gate voltage and the junction barrier to maximize the photovoltaic response. At an optimal gate voltage of +2 V, we obtain an open-circuit voltage of V_(oc) = 0.53 V and an efficiency of 1.9% under AM 1.5 1-sun solar illumination. This work demonstrates that the field effect can be used to modulate and optimize the response of photovoltaic devices incorporating grapheme.

Additional Information

© 2014 American Chemical Society. Received: March 11, 2014; Revised: July 14, 2014; Published: July 24, 2014. This research was supported in part by the Office of Energy Research, Materials Sciences and Engineering Division of the U.S. Department of Energy under Contract No. DE-AC02- 05CH11231, which provided for the design of the experiment and Raman spectroscopy characterization; the National Science Foundation within the Center of Integrated Nanomechanical Systems, under Grant EEC-0832819, which provided for photovoltaic response characterization; and by the Office of Naval Research (MURI) under Grant N00014-09-1066, which provided for graphene growth and device assembly. O.V.M. acknowledges the support of the Swiss National Science Foundation through the fellowship for Advanced Researchers PA00P2_145394. J.P.B. and H.A.A. acknowledge the support of the DOW Chemical Company. The authors also would like to thank to C. Ojeda-Aristizabal, J. Velasco, W. Regan, and Professor F. Wang for fruitful discussions.

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