ABSTRACT
The preparation of perovskite quantum dots (PQDs) using an in situ inkjet printing method is beneficial for improving the problems of aggregation and photoluminescence (PL) quenching during long-term storage. However, the stability of PQDs prepared using this method is still not ideal, and the morphology of in situ-printed patterns needs to be optimized. To address these problems, this study introduced polymethyl methacrylate (PMMA) into the process of in situ inkjet printing of PQDs and explored the effect of PMMA on the in situ patterning effect of PQDs. The results showed that using a mixed precursor solution containing a small amount of PMMA as the printing ink can slow down the shrinkage process of ink droplets and improve the uniformity of film formation. As the printing substrate, PMMA provided a suitable high-viscosity environment for the in situ growth of PQDs. This could effectively suppress the coffee ring effect. In addition, the interaction between the C=O=C group in PMMA and metal ion Pb2+ in the CsPbBr3 precursor molecules was favourable to enhancing the density of PQDs. The prepared PMMA-coated CsPbBr3 quantum dots (QDs) pattern had high stability and could maintain at 90.08% PL intensity after 1 week of exposure to air.
Subject(s)
Oxides , Quantum Dots , Titanium , Polymethyl Methacrylate , Calcium Compounds , InkABSTRACT
The three-primary-color chip array is the most straightforward to realize full-color micro-LED displays. However, the luminous intensity distribution shows high inconsistency between the AlInP-based red micro-LED and GaN-based blue / green micro-LEDs, resulting in the issue of angular color shift with different viewing angles. This Letter analyzes the angular dependence of color difference of conventional three-primary-color micro-LEDs, and proves that the inclined sidewall with homogeneous Ag coating has a limited angular regulation effect for micro-LEDs. Based on this, a patterned conical microstructure array is designed on the micro-LED's bottom layer to effectively eliminate the color shift. This design cannot only regulate the emission of full-color micro-LEDs to perfectly meet Lambert's cosine law without any external beam shaping elements, but also improve the light extraction efficiency of top emission by 16%, 161%, and 228% for red, green, and blue micro-LEDs, respectively. The color shift Δ u ' v ' of the full-color micro-LED display is also kept below 0.02 with the viewing angle ranging from 10° to 90°.
ABSTRACT
Two-dimensional organic-inorganic hybrid Ruddlesden-Popper perovskites have attracted a lot of attention due to their unique photochemical properties and enhanced stability towards photoluminescence devices. Compared with three-dimensional materials, two-dimensional perovskites show great potential for photoelectric applications due to their tunable band gap, great excitation binding energy, and large crystal anisotropy. Although the synthesis and optical properties of BA2PbI4 crystals have been extensively studied, the role of their microstructure in photoelectric applications, their electronic structure, and their electron-phonon interaction are still poorly understood. In this paper, based on the preparation of BA2PbI4 crystals, the electronic structure, phonon dispersion, and vibrational properties of BA2PbI4 crystals were revealed in detail with the help of density functional theory. The BA2PbI4 stability diagram of formation enthalpy was calculated. The crystal structure of the BA2PbI4 crystals was characterized and calculated with the aid of Rietveld refinement. A contactless fixed-point lighting device was designed based on the principle of an electromagnetic induction coil, and the points with different thicknesses of BA2PbI4 crystal were tested. It is proved that the excitation peak of the bulk is 564 nm, and the surface luminescence peak is 520 nm. Phonon dispersion curves and the total and partial phonon densities of states have been calculated for the BA2PbI4 crystals. The calculated results are in good agreement with the experimental Fourier infrared spectra. Besides the basic characterization of the BA2PbI4 crystals, the photoelectrochemical properties of the materials were also studied, which further proves the excellent photoelectric properties of the BA2PbI4 crystals and the broad application prospect.
ABSTRACT
CsPbX3 (X = Cl, Br or I) perovskite quantum dots (PQDs) have gained increasing interest due to their superior performance in photoelectric applications. In our work, a series of Mn2+ doped CsPbBr3 PQDs were successfully prepared in glasses by melt quenching and in situ crystallization technique. Due to the 4T1 (4G)â6A1 (6S) transition of Mn2+, a slight red shift from 510 nm to 516 nm was found, with the FWHM expansion from 18 nm to 26 nm. The PQDs@glasses showed excellent thermal stability, and the exciton binding energy reached a high level of 412 meV. The changes of the electronic structure after Mn doping CsPbBr3 can be demonstrated by first principles. Finally, a contactless electroluminescence device with the PQDs@glasses was designed based on the principle of electromagnetic induction, which is a potential application for detecting distance in sterile and dust-free environments.
