White organic light‐emitting diodes (WOLEDs) are superior to traditional incandescent light bulbs and compact fluorescent lamps in terms of their merits in ensuring pure white‐light emission, low‐energy consumption, large‐area thin‐film fabrication, etc. Unfortunately, WOLEDs based on multilayered or multicomponent (red, green, and blue (RGB)) emissive layers can suffer from some remarkable disadvantages, such as intricate device fabrication and voltage‐dependent emission color, etc. Single molecules, which can emit white light, can be used to replace multiple emitters, leading to a simplified fabrication process, stable and reproducible WOLEDs. Recently, the performance of WOLEDs by using single molecules is catching up with that of the state‐of‐the‐art devices fabricated by multicomponent emitters. Therefore, an increasing attention has been paid on single white‐light‐emitting materials for efficient WOLEDs. In this review, different mechanisms of white‐light emission from a single molecule and the performance of single‐molecule‐based WOLEDs are collected and expounded, hoping to light up the interesting subject on single‐molecule white‐light‐emitting materials, which have great potential as white‐light emitters for illumination and lighting applications in the world.

Five deep blue carbene-based iridium(III) phosphors were synthesized and characterized. Interestingly, one of them can be fabricated into deep blue, sky blue and white organic light-emitting diodes (OLEDs) through changing the host materials and exciton blocking layers. These deep and sky blue devices exhibit Commission Internationale de l'Éclairage (CIE) coordinates of (0.145, 0.186) and (0.152, 0.277) with external quantum efficiency (EQE) of 15.2% and 9.6%, respectively. The EQE of the deep blue device can be further improved up to 19.0% by choosing a host with suitable energy level of its lowest unoccupied molecular orbital (LUMO).

It has long been a challenge to achieve iridium(III) complexes with emission colors covering the whole visible and near‐infrared wavelengths, by using similar cyclometalating ligands. Herein, a series of iridium(III) complexes that accomplish broadly tunable phosphorescence from 420 to 729 nm through the use of trifluoromethyl substituents and other conjugated units such as [1,2,5]thiadiazolo[3,4‐c]pyridine in the cyclometalating ligands are reported. The peak external quantum efficiencies of 7.1%, 20.0%, 14.0%, 4.0%, and 16.0% are achieved for deep‐blue, green, red, near‐infrared, and white phosphorescent organic light‐emitting diodes, respectively, by using these iridium(III) complexes.

Advances in achieving high external quantum efficiency (EQE) of near‐infrared (NIR) organic light‐emitting diodes (OLEDs) are lagging behind that of the visible‐light OLEDs, according to the energy gap law. Herein, two structurally simple NIR‐phosphorescent Ir(III) complexes, DTCNIr and PTCNIr, with the cyclometalated ligands functionalized by the 1‐phenylisoquinoline‐4‐carbonitrile moiety and thieno/benzo[b]thiophene moiety are handily accessed within three synthetic steps. The introduction of the cyano unit can significantly lower the lowest unoccupied molecular orbitals whereas incorporating the conjugated group can elevate the highest occupied molecular orbitals of the newly designed Ir(III) complexes. The intramolecular charge transfer (ICT) transitions are enhanced due to the increased donor–acceptor interaction inside the metallophosphor. As a result, the emissions are red‐shifted to the NIR region with fast radiative decay. A maximum external quantum efficiency (EQE) of 8.11% with the emission peak at 726 nm for DTCNIr and a maximum EQE of 6.39% with the emission peak at 763 nm for PTCNIr are achieved in the NIR OLEDs by using these Ir(III) materials as the dopant emitters, a champion efficiency in the Ir(III)‐based OLEDs with the emission peak exceeding 760 nm.

A new strategy is developed in which cadmium‐doped zinc sulfide (CdZnS) is used as the outermost shell to synthesize red, green, and blue (RGB) quantum dots (QDs) with the core/shell structures of CdZnSe/ZnSe/ZnS/CdZnS, CdZnSe/ZnSe/ZnSeS/CdZnS, and CdZnSe/ZnSeS/ZnS/CdZnS, respectively. Firstly, the inner ZnS and ZnSe shells confine the excitons inside the cores of QDs and provide a better lattice matching with respect to the outermost shell, which ensures high photoluminescence quantum yields of QDs. Secondly, the CdZnS shell affords its QDs with shallow valence bands (VBs). Therefore, the CdZnS shell could be used as a springboard, which decreases the energy barrier for hole injection from polymers to QDs to be below 1.0 eV. It makes the holes to be easily injected into the QD EMLs and enables a balanced recombination of charge carriers in quantum dot light‐emitting diodes (QLEDs). Thirdly, the RGB QLEDs made by these new QDs exhibit peak external quantum efficiencies (EQEs) of 20.2%, 19.2%, and 8.4%, respectively. In addition, the QLEDs exhibit unexpected luminance values at low applied voltages and therefore high power efficiencies. From these results, it is evident that CdZnS could act as an excellent shell and hole injection springboard to afford high performance QLEDs.

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Tetrafluorinated phenylpyridine has been used to achieve sky blue-emitting iridium(iii) phosphors and their organic light-emitting diodes exhibit high external quantum efficiencies (∼20%) with cyan emission colours.

primary colors, red, green and blue (RGB) are crucial. [3] By harvesting both 25% singlet and 75% triplet excitons inside emissive layers (EMLs), phosphorescent OLEDs (PHOLEDs) have been proven to be one of the best candidates for lightemitting devices. [4][5][6][7] To date, green and red PHOLEDs fabricated by employing metallophosphors have shown the highest external quantum efficiencies (EQEs) of over 30%, which is satisfactory for industrial application. [8,9] However, for the deep blue PHOLEDs, especially when the Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of the y values are smaller than 0.1, they perform with relatively low EQEs. [10,11] On the one hand, it is really difficult and challenging to obtain efficient deep blue metallophosphors with a broad energy gap (E g ) between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). [12,13] On the other hand, the triplet energy (E T ) levels of the host and electron/hole transport layer (ETL/HTL) in the deep blue PHOLEDs are required to be higher than that of the high-triplet energy phosphor. [14][15][16] In general, these devices suffered from serious leakage of the excitons from the EML to its neighbor layers, which leads to a significant decrease of efficiency and Achieving efficient deep blue phosphorescent organic light-emitting diodes (PHOLEDs) is one of the most difficult and challenging targets nowadays, especially when the Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of y values are smaller than 0.1. Herein, tandem device architectures are fabricated by using an iridium(III) carbene phosphor. In the tandem structures, two electroluminescent units are stacked and connected by a charge generation layer (CGL) which consists of dipyrazino[2,3-f:2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HATCN) and 4,4′-(cyclohexane-1,1-diyl)bis(N,N-di-p-tolylaniline) (TAPC). Meanwhile, 4,6-bis(3,5-di(pyridine-3-yl)phenyl)-2-methylpyrimidine (B3PYMPM) and diphenyl-4-triphenylsilylphenyl phosphine oxide (TSPO1) are used as electron transport layers. The best device gives an external quantum efficiency of 32.3% with the CIE coordinates of (0.15, 0.10), which is among the most efficient blue PHOLEDs made by iridium(III) phosphors. The pure blue emission and high performance are mainly attributed to the efficient and balanced recombination of charge carriers in the two emissive layers, which successfully suppresses the exciplex formation and efficiently confines the triplet excitons.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/admi.202200932.