New Trends in the Use of Transition Metal–Ligand Complexes for Applications in Electroluminescent Devices

Abstract

The advantage of using phosphorescent transition metal–ligand complexes in optoelectronic applications such as organic light‐emitting diodes (OLEDs) and light‐emitting electrochemical cells (LECs) are described and evaluated. Additionally, different device constructions utilizing phosphorescent transition‐metal complexes like iridium(III) mixed‐ligand complexes and ruthenium(II) systems are reviewed and specified. Diverse host materials in which the phosphorescent emitters can be placed are discussed, such as small organic molecules and a few polymeric systems, and alternative processing technologies are briefly compared. Recent developments in the synthesis of iridium(III) triplet emitters are discussed. Different device architectures require different kinds of metal–ligand complexes. The different synthetic routes leading to charged and non‐charged complexes are briefly discussed.

π‐Conjugated Donor and Donor–Acceptor Metallo‐Polymers

“…The usage of Zn II ions leads to metallo-polymers being potential interesting light-emitting materials in OLEDs; [14,15,[21][22][23] moreover, also Ir-containing polymers are of special interest for this purpose. [24][25][26] In recent years, p-conjugated polymer semiconductors with donor-acceptor (D-A) architectures have attracted considerable attention, since their electro-optical properties make them promising candidates for potential applications in the fields of organic electronics. [27][28][29] In this contribution we describe the synthesis and characterization of four metallo-polymers containing either zinc(II) or ruthenium(II) ions in the main chain.…”

Highly phosphorescent perfect green emitting iridium(iii) complex for application in OLEDs

“…4,5 A large number of iridium complexes have been utilized for this purpose, which are mostly based on the cyclometalating ligand 2-phenylpyridine (ppy) with an auxiliary ligand such as acetylacetonate (acac) or picolinate (pic). [6][7][8][9][10] Several groups have demonstrated tuning of the phosphorescence wavelength from blue to red by functionalization of the ligands with electron withdrawing and electron donating substituents. [11][12][13] Nevertheless, no attempts were made to tune the colour purity by decreasing the emission bandwidth, which of course is attractive for both fundamental research and practical applications.…”

Cyclometalated Ir(III) Complexes for High-Efficiency Solution-Processable Blue PhOLEDs

“…They have the benefits of relatively short excited state lifetimes, high photoluminescence efficiency, good color tuneability and general thermal and electrochemical stability. 4,5,6 In this context the archetypal complex is the green emitter fac-Ir(ppy) 3 (ppy = 2-phenylpyridine). For blue emission electron-withdrawing substituents are attached to the phenyl ring of ppy ligands to decrease the HOMO energy while keeping the LUMO energy relatively unchanged.…”