Rapid Photonic Curing for the Fabrication of Strongly-Confined Colloidal Quantum Dot Transistors with High Carrier Mobility
Mohamad I. Nugraha a, Emre Yarali a, Yuliar Firdaus a, Yuanbao Lin a, Nimer Wehbe a, Abdulrahman El-Labban a, Emre Yengel a, Thomas D. Anthopolous a
a King Abdullah University of Science and Technology (KAUST) - Saudi Arabia, 4700 King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
Oral, Mohamad I. Nugraha, presentation 041
DOI: https://doi.org/10.29363/nanoge.iperop.2020.041
Publication date: 14th October 2019

Colloidal quantum dots (CQDs) are attractive semiconducting materials for broad optoelectronic devices, serving an ease of device fabrication compatible with low-temperature processing and low-cost deposition methods. Fabrication of CQD thin-film transistors (TFTs), is so far finalized with conventional thermal annealing, which requires prolonged processing time; yet it leaves insulating organic residues behind, suppressing charge carrier mobility (~10-2 cm2V-1s-1). Here we demonstrate a millisecond heat treatment of lead sulfide (PbS) CQD films using photonic curing, which results in high carrier mobility in TFT devices. In comparison with conventional thermal annealing, the photonic curing is found to effectively suppress organic residues, yet it preserves quantum confinement in the films. With increasing flashing power, the electron mobility on SiO2-gated devices increases up to 0.2 cm2V-1s-1, attributed to suppression and decomposition of organic residues, as revealed from ellipsometry and x-ray photoelectron spectroscopy (XPS) measurements. At high flashing power, the electron mobility decreases which is associated with the formation of traps and hole doping in the films. According to XPS analysis, we find that some of Pb atoms are ablated from the films, responsible for hole doping and dangling bond formation at high flashing power. Finally, we operate the PbS CQD TFTs with top gate configuration using polymethyl methacrylate (PMMA) and high capacitance polymer dielectrics, with their good interface and superior trap filling, enabling us to obtain high electron mobility of 0.48 and >1 cm2V-1s-1, respectively. Our works show the great importance of photonic curing for the fabrication of high performance CQD TFTs, standing out as effective replacement of conventional thermal annealing, which is potentially applicable for other optoelectronic applications such as CQD photodetectors and solar cells.

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