Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 5, Issue 3, Pages 822-827Publisher
AMER CHEMICAL SOC
DOI: 10.1021/am3023898
Keywords
carbon quantum dots; mobility; ligand exchange; ligand length; emulsion template; field-effect transistors
Funding
- Korea Research Foundation (KRF) through the National Research Laboratory Project
- POSCO Research Program for Fusion Technology of Materials
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We report electrical measurements of films of carbon quantum dots (CQDs) that serve as the channels of field-effects transistors (FETs). To investigate the dependence of the field-effect mobility on ligand length, colloidal CQDs are synthesized and ligand-exchanged with several primary amines of different ligand lengths. We measure current as a function of gate voltage and find that the devices show ambipolar conductivity, with electron and hole mobilities as high as 8.49 X 10(-5) and 3.88 X 10(-5) cm(2) V-1 s(-1) respectively. The electron mobilities are consistently 2-4 times larger than the hole mobilities. Furthermore, the mobilities decrease exponentially with the increase of the ligand length, which is well-described by the Miller-Abrahams model for nearest-neighbor hopping. Our results provide a theoretical basis to examine charge transport in CQD films and offer new prospects for the fabrication of high-mobility CQD-based optoelectronic devices, including solar cells, light-emitting devices, and optical sensors.
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