Application of Perovskite Quantum Film
Application of Perovskite Quantum Film – Perovskite Solar Cell Coatings – Cheersonic
With the popularity of flat-panel TVs and the improvement of living standards, people’s demand for display effects is also increasing, and color gamut has always been one of the important indicators for measuring display effects. Ordinary LCD TVs generally use blue-light GaN chips to excite YAG yellow powder as a backlight source, and their spectra interfere with each other in the red and green bands. After color filtering by liquid crystal glass, the half-peak width of RGB is very wide, the color purity is low, and the color gamut is low. NTSC The CIE 1931 color gamut is generally only about 68%~72%, and the image quality expression is poor. KSF technology improves a certain color gamut effect, but is limited by the green phosphor (wavelength, half-wave width, concentration), the color gamut value of this technology can only reach 183% in NTSC193183%, quantum dot technology because its spectrum is in the red The half-widths of the green and blue colors are very narrow, and the half-widths of the R, G, and B colors emitted after filtering are also very narrow. The single color has high purity and a high color gamut. The NTSC CIE 1931 color gamut is generally 100- About 120%.
The luminescence principle of quantum dots is similar to that of conventional semiconductors. The carriers in the material reach an excited state after receiving external energy, and release energy when the carriers return to the ground state. This energy is usually expressed as light. form is emitted. Different from conventional luminescent materials, Ziba photonic materials also have the characteristics of continuously adjustable emission wavelength, wide excitation spectrum and narrow emission spectrum, and extremely high fluorescence quantum yield.
At present, quantum dot materials are used in liquid crystal backlight in the form of optical film. The blue LED in the backlight module emits blue light. When the blue light passes through the quantum dot film, part of the blue light is converted into green light and red light by the quantum dots. Blue light, red light and green light emitted by quantum dots are combined to synthesize white light and become the light source of liquid crystal glass. At present, the application of quantum dot backlight display mainly focuses on the use of classical quantum dot materials with core-shell structure (especially CdSe materials). High-quality core-shell quantum dots are generally prepared by high-temperature hot injection method, and industrialization still faces challenges such as complex process and high cost. In addition, due to the toxicity of Cd2+, CdSe-based materials face severe environmental pressure. The European Commission announced its decision to ban TVs and monitors containing Cd in Europe from October 2019. Therefore, seeking new materials that meet the application of QLED backlight display is an important idea to solve the above challenges and achieve original breakthrough technologies. Compared with CdSe-like quantum dots that are in the process of industrialization, perovskite quantum dots have the characteristics of low cost and simple preparation process, which has advantages in the fields of light-emitting diodes and lasers, and has attracted the attention of academia and industry. A new type of display material with growth potential.
The structural formula of perovskite quantum dots is generally ABX, where A can be a small molecule organic cation or an inorganic metal cation, the B site is usually a Pb* ion, and X is a halogen (C1, Br. 1) anion. The crystal structure of perovskite dots consists of 1 B metal atom and 6 X atoms to form an octahedral structure, and the A atom is embedded in the center of a cubic structure formed by 8 octahedrons sharing 1 X atom in pairs. Compared with CdSe or lnP quantum dots in the process of industrialization, perovskite quantum dots have the characteristics of low cost, simple preparation process, and low material toxicity. At the same time, the luminescence performance of perovskite QDs is comparable to or even better than that of CdSe QDs: the emission spectrum covers the entire visible wavelength (410-700 nm), the fluorescence quantum yield (PILQY) is high (>90%), and the narrow emission peak ( Half-maximum width 20~50nm). It is noteworthy that the backlight display technology based on quantum dots has begun to be commercialized.
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