Carbon quantum dot-based field-effect transistors and their ligand length-dependent carrier mobility.

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 × 10–5 and 3.88 × 10–5 cm2 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 ...