Perovskite Quantum Dots (PQDs)
Perovskite generally refers to a kind of material with similar crystal structure to perovskite, which is composed of perovskite oxide (CaTiO3).
Depending on the atom/molecule used in the structure, perovskites possess an impressive array of interesting properties, including superconductivity, ferroelectricity, charge ordering, spin transport, and more. Therefore, perovskites bring exciting research directions for physicists, chemists and materials scientists.
Quantum dots (QDs), sometimes referred to as semiconductor nanocrystals (NCs), are tiny particles of semiconductor materials, between 2-10 nanometers (10-50) atoms in diameter. Quantum dots have properties that lie somewhere between bulk semiconductors and discrete atoms or molecules, and their photoelectric properties change with size and shape. Quantum dots would exhibit different optical and electronic properties than larger particles. In fact, QDS tend to show quantum size effects in their optical and electronic properties, such as tunable and efficient photonics (PL), having narrow emission, and photochemical stability. This is why QDS are incorporated as active components into a wide variety of devices and applications, some of which have already been commercialized, such as quantum dot-based displays.
Perovskite quantum dots (PQDs) are a kind of quantum dots based on perovskite materials. While the concept is relatively novel, they have been shown to have properties that match or exceed metallic chlous QDS: they are more tolerant to defects, have excellent photoluminescence quantum yields and high color purity. This property is very suitable for electronic and optoelectronic applications, so perovskite quantum dots have great potential in real life applications. Some of them have been formally put into production, including LED displays and quantum dot solar cells.
The latest Perovskite QD news:
1. An exploration of how carbon nanotube diameter affects the performance of photodetector heterojunctions1
Researchers from China's Hebei University of Technology and Chinese Academy of Sciences have found that increasing the diameter of single-wall carbon nanotubes (SWCNTs) in SWCNT/perovskite QD heterojunctions can improve the optoelectronic performance of the heterojunction between the two materials.
The team systematically tested the performance effects of varying diameters of SWCNTs, a single layer of carbon atoms that form a hexagonal lattice rolled into a seamless cylinder, with different band gaps, or the amount of energy required for an electron to conduct electric current, in heterojunction films with perovskite QDs. Their study indicated that increasing the diameter of SWCNTs improved the responsivity, detectivity and response time of this type of heterojunction film. This effect may be mediated by the enhanced separation and transport of photogenerated excitons, an energy-carrying, neutrally charged electron that combines with a positive electron hole, in the film.
2. Molecular dopants of TCI have facilitated the development of organic electronics2-6
TCI has launched a range of molecular dopants that can significantly increase the charge carrier density and modify the energy levels in organic electronics devices. Molecular dopants offer a versatile platform to tune the optoelectrical and electrical properties of organic semiconductors to application-specific demands, allowing advantages like increasing the electrical conductivity and mobility by orders of magnitude and improving contact properties in various electronic and optoelectronic devices.
TCI's p-type and n-type dopants can be applied to various organic electronics devices, such as: carrier transport layers of organic light-emitting diodes (OLEDs), organic photovoltaics (OPVs), perovskite solar cells (PSCs), and perovskite quantum dot LEDs, as well as active layers of organic field-effect transistors (OFETs), OPVs, and thermoelectric devices in the field of organic electronics research.
3. Canon has developed perovskite quantum dot inks that can be used in next-generation displays
Canon has announced that it has developed perovskite quantum-dot inks for use in next-generation displays, with improved durability and potential for application in high-image-quality displays.
Quantum dots are semiconductor nanocrystals that measure only a few nanometers in diameter and can emit light with high brightness and high color purity. Displays with quantum-dot technology are attracting growing attention due to their wide color gamut that makes possible high visual expressiveness. Therefore, quantum dots for display is sought to achieve higher color purity and higher light utilization efficiency. In addition, though cadmium (Cd) has thus far been the preferred material for quantum dots, due to environmental concerns, there is a growing interest in Cd-free materials.
4. Design of Novel Polymer Hole Transport Materials (HTMs) for Perovskite Quantum Dots7
Researchers from Korea's Pohang University of Science and Technology (POSTECH), Ajou University, Daegu Gyeongbuk Institute of Science and Technology (DGIST) and Kookmin University have designed new polymeric hole transport materials that constitute a crucial element in perovskite quantum dot solar cells, leading to significant increase in their efficiency.
The team's hole transport materials include polymers based on sulfur and selenium compounds. These polymers exhibit structural features, such as planarization and locking of intermolecular arrangements, which increase charge mobility. Furthermore, asymmetric alkyl substituents of the polymers facilitate molecular interactions, thereby complementing the electrical properties of cells.
5. Perovskite quantum dots were used to fabricate full color flexible microLED8
Researchers from Korea's KIMM institute have fabricated full-color flexible microLED devices, using blue LEDs and perovskite quantum dot color conversion layers. The demonstrated device featured 1 mm pixel pitch LEDs (25.4 PPI) and could be bent with a radius of 5 mm without being damaged.
The researchers used a perovskite-QD and siloxane composite using ligand exchanged PQD with silane composite followed by surface activation by an addition of halide-anion containing salt. Due to this surface activation, the researchers say that it was possible to construct the PQD surface with a silane ligand using a non-polar organic solvent that does not damage the PQD. As a result, the ligand-exchanged PQD with a silane compound exhibited high dispersibility in the siloxane matrix and excellent atmospheric stability.
6. Construction of ultraviolet radiation measurement device using perovskite quantum dots9
A team of researchers from China's Chinese Academy of Sciences (CAS), Jilin University and Beijing Institute of Technology, has used perovskite and quantum dots to build an ultraviolet radiation measurement device.
Measuring the intensity of ultraviolet light in outdoor conditions is important because more intense UV light can lead to faster sunburns and potentially to skin cancer in later years. In this new study, the researchers built a wearable device that can measure ultraviolet radiation in real-time and send the information to a smartphone.
7. New method for synthesis and analysis of blue quantum dots based on perovskite10
Researchers from The University of Tokyo and Yamagata University have addressed the difficulty in creating blue quantum dots by developing a unique self-organizing approach for producing lead bromide perovskite quantum dots. The research also incorporates cutting-edge imaging technology to characterize these novel blue quantum dots.
Quantum dots (QDs) are used in optoelectronic devices and quantum computing, among other things, and are referred to as "artificial atoms" due to their confined and distinct electronic properties. Quantum dots have characteristics that fall in between those of bulk semiconductors and individual atoms and molecules. Their photoelectric qualities vary depending on their size and shape. Quantum dots (QDs) are considered attractive materials for the emissive constituent of light-emitting diodes (LEDs) due to their high color intensity in a small spectral region, facile color tunability, and notable stability. Moreover, QD-based materials exhibit refined colors, longer lifetimes, reduced production costs, and lower energy requirements compared to typical luminescent materials used in organic light-emitting diodes (OLEDs).
8. A perovskite-based narrow-spectrum blue quantum dot emitter10
Researchers from the University of Tokyo have made progress with the development of blue-emitting quantum dots, which is seen as highly challenging. They have shown that using a new bottom-up design strategy and self-organizing chemistry can help create a high purity blue-emitting QD material (with a narrow emission spectrum).
The newly developed QDs have a special chemical composition that combines both organic and inorganic substances, such as lead perovskite, malic acid, and oleylamine. The materials self-aligned into a cube of 64 lead atoms. The lead researcher, Professor Eiichi Nakamura, says that "it took over a year of methodically trying different things to find that malic acid was a key piece of our chemical puzzle".
9. High-resolution perovskite nanocrystal graphics techniques for display11
Researchers from the Ulsan National Institute of Science and Technology (UNIST) have teamed up with researchers from Daegu Gyeongbuk Institute of Science and Technology (DGIST) to develop a patterning technique for the production of perovskite nanocrystal displays which are ultra-thin and high-resolution. The production involves a very simple stamp-like printing process that will facilitate the commercialization of the new technique.
The technique reportedly enabled the team to produce a display with RGB pixel patterns of 2,550 pixels per inch, which is about 400 percent higher resolution than the latest high-end smartphones.
References
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7. Dae Hwan Lee, Seyeong Lim, Chanhyeok Kim, Han Uk Lee, Dasol Chung, Yelim Choi, Jongmin Choi, Younghoon Kim, Sung Beom Cho, Hong Il Kim, and Taiho Park ACS Energy Letters 2023 8 (4), 1839-1847. https://doi.org/10.1021/acsenergylett.3c00211
8. Shim, H.C., Kim, J., Park, S.Y. et al. Sci Rep 13, 4836 (2023). https://doi.org/10.1038/s41598-023-31945-6
9. Yiqiang Z., Yaowen W., Zhexin L. et al. MATTER 2023 VOLUME 6, ISSUE 2, 506-520. https://doi.org/10.1016/j.matt.2022.11.020
10. Olivier J. G. L. Chevalier, Takayuki Nakamuro, Wataru Sato, Satoru Miyashita, Takayuki Chiba, Junji Kido, Rui Shang, and Eiichi Nakamura. Journal of the American Chemical Society 2022 144 (46), 21146-21156. https://doi.org/10.1021/jacs.2c08227
11. JONG IK KWON, GYURI PARK, GWANG HEON LEE et al. SCIENCE ADVANCES 2022 Vol 8, Issue 43. https://doi.org/10.1126/sciadv.add0697