Atomic layer deposition for quantum dots based devices
Quantum dots (QDs) are typical semiconductor nanocrystals with tunable band gaps, excellent photoluminescence efficiency and high extinction coefficient. And they are widely used in photodetectors, solar cells, light-emitting diodes (LED) and field effect transistors (FET).However, the photoluminescent quantum yield (PLQY) of QDs is severely limited by dangling bonds and trap states on the surface. In addition, the large specific surface area and exposed atomic sites are susceptible to the water/oxygen/light/heat in the environment. At the device level, the interface non-radiative recombination loss seriously affects the photoelectric performance of the quantum dot based device. Therefore, low photoelectronic efficiency and poor lifetime become the main obstacles for the further commercialization of quantum dots. As a cross-scale fabrication technique, atomic layer deposition (ALD) meets the requirements of QD device fabrication and has been used in the modification of QDs and QDs-based devices. It is suitable for surface defects passivation, dense thin film encapsulation, interstitial infilling and interface functional layers fabrication due to the characteristics of energy-dependent self-limiting reactions, dense uniform thin film fabrication, gas-phase infiltration and atomic level thickness control.
Figure 1 The corresponding challenges of QDs. (I) Non-radiative recombination corresponding to photoluminance decay; (II) High specific surface area corresponding to degradation and failure; (III) Long chain ligands corresponding to poor carrier transport; (IV) Interfacial carrier accumulation and recombination corresponding to heat and efficiency roll-off.
In this paper, the research group of Prof. Chen from Huazhong University of Science and Technology (HUST) reviewed the works of ALD on the QDs modification to improve the photoluminance, stability, carrier mobility, as well as device efficiency. ALD proves to be successful in the photoluminance quantum yield (PLQY) enhancement due to the elimination of QDs surface dangling bonds and defects. The QDs stability and devices lifetime are improved greatly through the introduction of ALD barrier layers. Furthermore, the carrier transport is ameliorated efficiently by ALD infilling into QDs interstitial space. Attributed to ALD ultra-thin and dense coating on the interface, the optoelectronic performance improvement is achieved. Finally, the challenges of ALD applications in QDs at present and several prospects including ALD process optimization, in-situ characterization and computational simulations are proposed. The article is entitled “Atomic layer deposition for quantum dots based devices” and published in Opto-Electronic Advances Vol. 9 2020.
About The Group
The micro-nano materials design and manufacturing research center is an interdisciplinary innovation platform based on the school of mechanical science and engineering, and the school of materials science and engineering. The center currently has 5 professors, 3 associate professors, 5 research assistants, and dozens of graduate students. The center focuses on the material manufacturing related topic in micro-nano scale including modeling and simulation, big data technology, atomic layer deposition, 3D printing technology as well their applications in optoelectronic devices, catalysis and biological health. The team has published more than 400 peer-review articles in Science, Advanced Materials, Nat. Commun., Angew. Chem. Int. Ed., and been authorized more than 100 patents (4 international patents).The team has also utilized some of the research achievements in industry, and maintained long-term and close cooperation with leading research centers and enterprises such as Stanford linear accelerator center, Intel corporation and TCL group.
Zhou B Z, Liu M J, Wen Y W, Li Y, Chen R. Atomic layer deposition for quantum dots based devices. Opto-Electron Adv 3, 200004 (2020).