Single crystal perovskite to change luminescent materials? Guoxing Photoelectric Disclosure Laboratory has prepared ultra-large crystals

Recently, Guoxing Optoelectronics said on the investor interaction platform that ultra-large-size single crystal perovskite crystals have been prepared through the laboratory. This research has great application value in luminescent materials, but from laboratory to practical application. There is still a long time in the product.

Perovskite has gradually entered the industry's sight in recent years. At present, inorganic LEDs based on conventional inorganic semiconductor materials commonly used in the market mostly adopt epitaxially grown quantum well structures, which are complicated in preparation process, demanding on materials, and high in energy consumption.

Professor Wang Jianpu, deputy dean of the Advanced Materials Research Institute of Nanjing University of Technology, said: "Organic light-emitting diodes (OLEDs) are different from inorganic LEDs. They are not limited by the preparation process. Large-size flexible devices can be prepared by solution/vapor deposition. The advantages of substitution have been initially applied to electronic products such as mobile phones and televisions. However, there are still limitations in the scope of application of OLEDs. The main reason is that the efficiency and stability of the devices and the manufacturing costs need to be further improved."

The organic-inorganic hybrid perovskite material has the advantages of organic and inorganic semiconductor materials, is suitable for solution processing of organic semiconductor materials and large-area film-forming preparation process, and has the defects of low defect density and high luminous efficiency of conventional inorganic luminescent materials. Good color purity and other advantages. Academician Huang Wei has accumulated and explored many years in the field of organic optoelectronics. Based on this, the team pioneered the research of perovskite LED in China.

According to the academic director of IAM and the president of Nanjing University of Technology, Academician Huang Wei, the two-dimensional perovskite material has low luminous efficiency, and the three-dimensional perovskite material has poor film formation and stability.

The perovskite luminescent material having a multi-quantum well structure has the advantages of high film-forming quality of the two-dimensional perovskite material and high luminous efficiency of the three-dimensional perovskite material.

Using this multi-quantum well perovskite material with adjustable dimensions, the external quantum efficiency of the LED device is 11.7%, and the energy conversion efficiency is 5.5% at a current density of 100 mA cm-2.

Recently, Professor Huang Wei and Professor Wang Jianpu made a major breakthrough in the research of perovskite light-emitting diodes (LEDs). They innovatively designed and prepared a perovskite LED with multiple quantum well structures, and its device efficiency and The stability far exceeds other perovskite LEDs reported by international peers, opening up new research directions for perovskite materials and their research in the field of luminescence.

This important research result was recently published in the international top academic journal NaturePhotonics.

Academician Huang Wei said, "This is the world's highest record of perovskite LEDs. This breakthrough in technology has opened up a new direction for perovskite materials and their research in the field of luminescence. It is also expected to be gradually developed on the basis of further research. Realize industrialization."

"Normally, the inorganic LED light-emitting tube adopts point-type illumination, which cannot be used as a display screen. The organic light-emitting diode (OLED) can be used as a display screen, but the perovskite LED is different from the traditional inorganic LED, and can not only be used as a display screen, but also made. The display screen is more vivid than the existing oled color." Wang Jianpu introduced.

"Because of its high efficiency, the price of the display made by perovskite led will be much cheaper. Take the 5 inch Samsung mobile phone as an example, the display price is expected to be reduced by 50%." Wang Jianpu said that the perovskite led application is in the lighting. The advantage is also obvious. The traditional LED dot-like illumination is a planar illumination, which makes the indoor light closer to natural light. Moreover, their research results can also be made into a large-scale product similar to the ceiling.

Previously, a joint research team from Cambridge University, Oxford University and the University of Munich in Germany demonstrated a new application area for perovskite materials: high-brightness LEDs for the preparation of various colors.

It is understood that the research team used a class of organometallic halide perovskite materials containing lead, carbon-based ions and halide ions, which are easily soluble in common solvents and form perovskite crystals after drying. The preparation process is low and simple.

By designing the diode structure, the researchers confined the charge to a very thin layer of perovskite, creating conditions for the electron-hole capture process to achieve luminescence.

The preparation process of the perovskite LED is simple and can be manufactured on a large scale: the perovskite solution is spin-coated on the substrate without a high temperature heating step and high vacuum conditions.

According to the project leader and Professor Sir Richardson, from the Cavendish Laboratory of Cambridge University, through the above simple process, it is still possible to exhibit very obvious semiconductor properties without the complicated purification process required by semiconductors such as conventional silicon.

It is understood that the first commercial perovskite LED is expected to be available within five years.

Another research team from Florida State University, physics assistant professor HanweiGao (transliteration: Gao Hanwei) and associate professor of chemical engineering BiwuMa (transliteration: Ma Biwu) are also using a class of materials called organometallic halide perovskites to make a high Performance LED.

They published the results in the journal Advanced Materials. “Early work found that perovskites may be a promising material in the production of LEDs,” Gao Hanwei said. “But its performance has not yet reached its full potential. We believe there is significant room for improvement.”

In the past, other researchers have tried to make LEDs with perovskites, but none of them have been particularly efficient. Gao Hanwei and Ma Biwu believe that the organic-inorganic mixture can make LEDs perform better if the formula is properly adjusted.

“When we think about this type of material, we know that it should perform better,” Ma Biwu said. “We have come up with new ways to solve some of the key issues to create high performance LEDs.”

After months of experimentation in which device structure was controlled by fine-tuning material properties and equipment engineering through synthetic chemistry, they eventually produced high-performance LEDs that exceeded expectations.

The material is exceptionally dazzling. It has been measured that its luminous intensity is about 10,000 candelas per square meter at a driving voltage of 12V. Generally speaking, as far as the computer screen is concerned, the LED with a luminous intensity of about 400 cds per square meter is bright enough.

"This extraordinary brightness depends to a large extent on the high luminous efficiency inherent in this surface-treated, highly crystalline nanomaterial," Gao Hanwei said.

The production of this material is quick and easy. In the lab, Gao Hanwei and Ma Biwu can make this material in about an hour, and in about half a day, they can create a complete device and test it.

In addition, although bare-mixed perovskites are unstable in moist air, nanostructured perovskites have good stability due to their specially designed surface chemistry. This chemical stability greatly reduces the facility requirements for making this new type of LED and will be of great benefit to cost-effective production in the future.

This research is critical to the advancement of LED technology and is rapidly becoming a channel for reducing electricity consumption.

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