A Review: Blue Fluorescent Zinc (II) Complexes for OLEDs—A Last Five-Year Recap

Abstract

Blue emissions in organic light-emitting diodes (OLEDs) are essential for their application in solid-state lighting and full-colour flat panel displays. On the other hand, high-power blue emitters are still uncommon, especially those that can achieve the Commission Internationale de l’Eclairage (CIE, X, Y) coordinates of (0.14, 0.08) in the National Television System Committee (NTSC) blue standard and have high external quantum efficiencies (EQE) of more than 5% because their molecular design presents an enormous challenge. Therefore, creating effective, stable, pure, and deep blue fluorescent materials is vital. Here, it is addressed how useful blue fluorescent Zn (II) complexes are for making organic light-emitting diodes (OLEDs). Utilizing Zn (II) complexes is appealing because of their favourable luminous characteristics, acceptance and mobility, and affordability. This mini-review article aims to provide an overview of Zn (II) complexes that emit blue fluorescent light and have been reported since 2018, while highlighting the unique qualities that make them appropriate OLED materials.

Zinc Complexes of Fluorosubstituted N-[2-(Phenyliminomethyl)phenyl]-4-methylbenzenesulfamides: Synthesis, Structure, Luminescent Properties, and Biological Activity

“…OLEDs were made using zinc complexes as emissive layers, for which the maximum brightness was from 950 to 8120 cd/m 2 with a current efficiency of 6.9 to 21.1 cd/A. Obtained results are comparable and even higher in some cases with the same class of luminophores [28][29][30][31][32]. The obtained azomethines and zinc(II) complexes were tested for their protistocidal, fungistatic, and antibacterial activities.…”

Zinc (II) complexes with Schiff bases obtained from N‐[2‐(cyclohexyliminomethyl)‐ or 2‐(4‐cyclohexylphenyliminomethyl) phenyl]‐4‐methylbenzenesulfonamides and their application as highly luminescent blue emitters for OLEDs

“…27,28 The blue light emission of OLEDs is important for their applications in solid-state lighting and full-color flat panel displays. Recent papers [29][30][31] have reviewed a number of blue fluorescent Zn(II) complexes based on Schiff bases for the fabrication of OLEDs, but their quantity and luminescent characteristics are still far from what is required in the industry.…”

Novel Fluorescent Tetrahedral Zinc (II) Complexes Derived from 4-Phenyl-1-octyl-1H-imidazole Fused with Aryl-9H-Carbazole and Triarylamine Donor Units: Synthesis, Crystal Structures, and Photophysical Properties

“…The unique properties of imidazole-based complexes, such as excellent electrochemical and photoluminescent properties, excellent thermal properties, and ease of modification, were taken into account in the design of various host materials such as electron transport, fluorescent, or phosphorescent molecules [19][20][21][22][23]. Over the years, several articles have reported the coordination of imidazole-based synthons with a variety of metal ions, including cobalt, nickel, iron, zinc, copper, and iridium, leading to the preparation of stable organic metal complexes [9][10][11][12][13][24][25][26][27]. In particular, d 10 transition zinc (II) complexes have become the focus of an ever-growing research area owing to their attractive luminescence and the low cost of zinc metal sources [2,9,[27][28][29].…”