Journal
NANO LETTERS
Volume 16, Issue 11, Pages 6761-6766Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.6b02354
Keywords
hot carrier; graphene; photovoltaic devices; two-dimensional (2D) materials; F4-TCNQ; Gr-TiOx-Ti heterostructures
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Funding
- Universidad de Costa Rica
- CELEQ
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Hot carriers in semiconductor or metal nanostructures are relevant, for instance, to enhance the activity of oxide-supported metal catalysts or to achieve efficient photodetection using ultrathin semiconductor layers. Moreover, rapid collection of photoexcited hot carriers can improve the efficiency of solar cells, with a theoretical maximum of 85%. Because of the long lifetime of secondary excited electrons, graphene is an especially promising two-dimensional material to harness hot carriers for solar-to-electricity conversion. However, the photo response of thus far realized graphene photoelectric devices is mainly governed by thermal effects, which yield only a very small photovoltage. Here, we report a Gr-TiOx-Ti heterostructure wherein the photovoltaic effect is predominant. By doping the graphene, the open circuit voltage reaches values up to 0.30 V, 2 orders of magnitude larger than for devices relying upon the thermoelectric effect. The photocurrent turned out to be limited by trap states in the few-nanometer-thick TiOx layer. Our findings represent a first valuable step toward the integration of graphene into third-generation solar cells based upon hot carrier extraction.
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