Bright and Stable Luminescence of CsPbX₃ Nanocrystals in ZrO₂ Skeletons for White Light Emitting Diodes

Abstract

Inorganic perovskite (CsPbX 3 , X = Cl, Br, and I) nanocrystals (NCs) have been recognized as ideal luminescent materials for display fields owing to their superior optical and electronic properties. However, the poor stability of NCs seriously restricts practical applications. In this paper, CsPbX 3 NCs with different emitting colors from blue to red were encapsulated in ZrO 2 skeletons in situ using a hot injection method to overcome poor stability. The CsPbX 3 NCs were well dispersed in ZrO 2 skeletons, in which the photoluminescence (PL) properties were improved. On the one hand, the NCs with brighter PL, higher stability, and narrower PL spectrum were obtained by in situ growth. On the other hand, these perovskite NCs were embedded in white powder ZrO 2 , effectively preventing its deterioration in wet and light conditions. The fluorescence of the composites was regulated by controlling the proportion of halogen ions in the CsPbX 3 @ZrO 2 composite. A flexible thin film with bright luminescence and high stability was prepared. Furthermore, CsPbX 3 @ZrO 2 composites were applied to make simple light emitting diodes (LEDs). White LEDs were fabricated by using blue-emitting CsPb(Cl/Br) 3 @ZrO 2 , green-emitting CsPbBr 3 @ZrO 2 , and red-emitting CsPb(Br/I) 3 @ZrO 2 composites. The Commission Internationale de I'Eclairage color coordinates of the white LEDs were (0.31, 0.33) and are within the white light range. This work provides an effective strategy for binding perovskite NCs to inorganic substrates for luminescent display fields.

Slowing Down the Hot Carrier Relaxation Dynamics of CsPbX3 Nanocrystals by the Surface Passivation Strategy

“…All inorganic lead halide perovskites (LHPs), CsPbX 3 (X = Cl/Br/I), have attracted attention as one of the most affordable emitters with promising performance in several optoelectronic applications such as light-emitting diodes, photodetectors, lasers, etc. − Exceptional characteristic features, essentially a wide absorption cross-section, tuneable band gap, long carrier lifetime, high photoluminescence quantum yields (PLQYs), and excellent charge transport properties of CsPbX 3 , are largely responsible for their performance in optoelectronic applications. − The operation of optoelectronic devices is strongly dependent on the dynamics of the photo-excited charge carriers, which influences various ultrafast processes, such as hot carrier (HC) relaxation, carrier recombination, and ultrafast carrier transfer dynamics. , Generation of carriers above the conduction band by excitation energy larger than the band gap of the semiconductor leads to the formation of HCs with a temperature higher than the lattice temperature. The rapid cooling (in sub-ps time) of these HCs to the band-edge through the loss of their excess energy through carrier–carrier scattering and carrier–phonon scattering is a major energy loss channel. − Hence, the mitigation of heat energy losses through the extraction of the HCs before cooling in the band-edge enables to achieve the power conversion efficiency beyond the Shockley Queisser limit. ,, Therefore, delaying the HC relaxation time is an essential task before we design efficient photovoltaic devices.…”

CsPbX3 (X = Cl, Br, and I) Nanocrystals in Substrates toward Stable Photoluminescence: Nanoarchitectonics, Properties, and Applications

“…We have developed bright CsPbX 3 NC-incorporated ZrO 2 skeletons (CsPbBr 3 @ZrO 2 composites) recently and were able to apply this material for use in the color conversion layer of the white LED, with the schematic illustration of the synthesis processes shown in Figure and some of the other characterization data collected shown in Figure , confirming the formation of the ZrO 2 phase. ,− A solvothermal treatment method was required to construct the white ZrO 2 skeleton-like base, whereas the hot injection method was applied to attain in situ encapsulation of blue- to red-emitting CsPbX 3 NCs on these ZrO 2 skeletons to obtain a type I CsPbBr 3 @ZrO 2 heterojunction …”

“…Example of the construction processes for the synthesis of ZrO 2 skeletons and CsPbBr 3 @ZrO 2 composites. All panels are reproduced from ref . Copyright 2022 American Chemical Society.…”

“…The display device has become one of the most important information output instruments in modern society and has been widely utilized in a variety of devices involving cell phones, computers, televisions, etc. , Among these, light-emitting diodes (LEDs) constructed using luminescent semiconductor nanocrystals (NCs) have emerged as one of the leading technologies in the flat-panel displays market. , Unlike classic colloidal II–VI (e.g., CdTe and CdSe), III–V (e.g., InP), and ternary I–III–VI (e.g., CuInS 2 ) NCs, luminescent perovskite materials often possess relatively low nonradiative recombination rates and high color purity, which make them competitive candidates in the fields of LEDs and lasers. − Because of the rich morphologies (in the form of nanoplatelets (NPLs), nanosheets (NSs), nanowires (NWs), quantum dots (QDs), etc.) and abundant structures (ranging from zero dimensional (0D) to three-dimensional (3D)) as well as the outstanding photoluminescence (PL) properties of the perovskite nanomaterials, these materials have been widely studied for a variety of applications.…”

Fabrication of Photostable Siloxane-Coated Quantum Dots for White-Light-Emitting Diodes

“…Semiconductor nanocrystals (quantum dots, QDs) have attracted more and more attention due to their unique characteristics, such as size-dependent multicolor luminescence, narrow fluorescence peak, high photoluminescence quantum yield (PL QY), and high photochemical stability. − The outstanding properties of QDs made them a substitute material for many applications including solar cells, quantum dot light-emitting diodes (QLEDs), biosensor detection, and so on. − Recently, the new QDs/polymer composites became the favorite candidate to replace the traditional phosphor materials with excellent performance in the field of lighting. However, there were still many challenges for the long-term practical application of QD composites due to the intrinsic unstable properties of QDs and the incompatibility between QDs and polymer composites. − In order to improve the stability of QDs, a lot of efforts were devoted to growing shells outside QDs, such as ultra-thick shell QDs, silica-coated QDs, Al 2 O 3 -encapsulated QDs, and mixed QDs with inorganic salt. − But this may bring a new problem of the surface incompatibility between QDs with the widely used polymer matrix or silicone resins, resulting in uncontrolled aggregation or phase separation of QDs. This could cause the spectral shift of QD/polymer composites when QDs were applied to micro-LED, thus affecting the device performance.…”