Technical / research - Page 49

Researchers from the Beijing Institute of Technology and MIIT Key Laboratory for Low Dimensional Quantum Structure and Devices have developed perovskite quantum dots microarrays with strong potential for quantum dots color conversion (QDCC) applications, including photonics integration, micro-LEDs, and near-field displays.

QDCC is considered a versatile way to achieve full-color organic light-emitting diodes and micro-light-emitting diodes displays. QDCC provides a wide range of color performance and easy integration. However, conventional QDCC pixels, fabricated by the commonly used method of inkjet printing, tend to be too thin to achieve efficient color conversion. The conventional combination of quantum dots and coffee-ring effects or puddle of particle-laden liquid that occur after evaporation, lowers the light conversion efficiency and emission uniformity in quantum dot microarrays. This also contributes to blue-light leakage or optical crosstalk, where unwanted coupling occurs between signal paths. 

Researchers from the City University of Hong Kong and the Southern University of Science and Technology in Shenzhen, China, have shown that a self-assembled monolayer can facilitate the formation of a large-area perovskite film using a blade-coating process, thus promote the upscaling of perovskite photovoltaic technology.

Researchers build perovskite solar cells with layers of material deposited on an underlying substrate. In adapting the high-speed blade-coating method for perovskite thin-film deposition, the researchers realized that the surface properties of the substrate are critical for large-area coating and perovskite growth. The current process leaves voids at the buried interface of the perovskite film that is detrimental to the device performance. “To solve this problem, we have screened various hole-transporting materials and found that self-assembled monolayers are a class of promising materials for the upscaling of perovskite devices,” said Alex Jen, a professor at City University of Hong Kong.

Scientists from Imperial College London, the University of Surrey, the University of Nottingham, research institute UCL, Switzerland-based Fluxim and London South Bank University have designed a perovskite solar cell that integrates a ferrocene co-mediator interlayer at the interface between the spiro-OMeTAD hole transport layer (HTL) and the active perovskite material.

The team noted that the migration of lithium is critical in the degradation of spiro-OMeTAD-based devices, which is accelerated at higher temperatures, leading to the rapid degradation of the perovskite. The scientists described ferrocene as a sandwich structured material that is highly stable and can be used as a low-cost transition metal complex.

Researchers from Chonnam National University in South Korea, Shivaji University in India, the Belgian research institute KU Leuven and Cardiff University in the UK have built an all-inorganic perovskite solar cell with a terbium doped solar absorber, which reportedly increases thermal stability.

The scientists developed a low-cost and simple hot-air method and also used terbium doping and quantum passivation techniques to stabilize the perovskite phase in the ambient conditions - with all processes carried out in ambient conditions.

Scientists at Russia's NUST MISiS, Moscow Institute of Physics and Technology, the Russian Academy of Sciences, RTU MIREA and Italy's CHOSE (Centre of Hybrid and Organic Solar Energy) have developed a halide perovskite-based material for use in high-speed and highly sensitive ionizing radiation detectors.

Perovskite responds to ionizing radiation in the form of light (luminescence) or current (as a photodiode). This is useful for high-speed and high-sensitivity components for high-energy particle registration. However, the structures inside the collider are exposed to high doses of radiation, which can damage them. Accordingly, components of ionizing radiation detectors must be resistant to such effects and retain their properties for a long time.

Researchers from the UK's University of Cambridge and Diamond Light Source, working with scientists from Japan's Okinawa Institute of Science and Technology (OIST), have found that the defects which limit the efficiency of perovskites are also responsible for structural changes in the material that lead to degradation.

In their work, the researchers used a combination of techniques to mimic the process of aging under sunlight and observe changes in the materials at the nanoscale, helping them gain new insights into the materials. Their findings could accelerate the development of long-lasting, commercially available perovskite photovoltaics.

Researchers from the University of the Basque, University of Trieste and the Basque Research and Technology Alliance (BRTA) have managed to improve the stability and power conversion efficiency of a solar cell based on methylammonium (MA)-formamidinium (FA) lead halide perovskite, by using graphitic and amorphous nitrogen-doped carbon dots (g-N-CDs) as an additive.

In their study, the team set out to examine the influence of carbon dot additives on he efficiency and stability of PSCs. They found that the stability of the g-N-CDs-containing cells was improved. The long-term evaluation of the performances of the cells showed improvement of the power conversion efficiency of the g-N-CDs-containing cells over time, up to 109% of the initial efficiency after 40 days while the reference performance without CDs dropped to 86%.

Researchers from ARC Centre of Excellence in Exciton Science, Monash University, University of Sydney and CSIRO Manufacturing have shown how water could be the 'secret ingredient' in a simple way to create perovskite crystals.

Ordinarily, water is kept as far away as possible during the process of creating perovskites as the presence of moisture is severely harmful to them. That’s why perovskites for scientific research are often made via spin coating in the sealed environment of a nitrogen glove box. However, in their new work, the researchers have found a simple way to control the growth of phase-pure perovskite crystals by harnessing water as a positive factor. This liquid-based mechanism works at room temperature, so the approach remains cost effective.

Researchers from The Hong Kong University of Science and Technology, Heilongjiang University, City University of Hong Kong and Sun Yat-sen University have developed a novel technique to fabricate perovskite-based light-emitting diodes using quantum confinement.

According to theory, by adjusting the compositions of the halide being used, i.e., iodine, bromine, and chlorine, the color of the emission may be fine-tuned. Nevertheless, color instability caused by migration of ions and separation in blended halides impedes the future development of perovskite-based LEDs, particularly blue perovskite-based LEDs, which require significantly higher voltages for proper operation. A potential strategy for achieving color controllability in perovskite-based LEDs is to use perovskite-based nanostructures which utilize quantum confinement.

Researchers from Korea's Sungkyunkwan University and Gyeongsang National University have developed an innovative technique to develop transparent displays with high resolution and flexibility using perovskite materials.

Solution-based perovskites have been attracting attention in the area of display technology for many years, due to their exceptional optical-based electronic characteristics and ease of preparation. Owing to the benefits of solution-based perovskites, researchers have long envisioned the commercial adoption and implementation of flexible transparent displays.