Homoleptic platinum(ii) complexes with pyridyltriazole ligands: excimer-forming phosphorescent emitters for solution-processed OLEDs

Abstract

Two new homoleptic platinum(ii) complexes are reported that feature aryl-appended 5-(2-pyridyl)-1,2,4-triazole chelates acting as N^N− ligating ions, PtL12 and PtL22. They have been used to prepare high-efficiency OLEDs, in which unimolecular and bimolecular excited states contribute green and red emission respectively.

The role of dinuclearity in promoting thermally activated delayed fluorescence (TADF) in cyclometallated, N^C^N-coordinated platinum(ii) complexes

“…As demonstrated before, the kinetic relationship between bimolecular and unimolecular photoluminescence lifetimes in solution is not preserved in solid film (Figure S5.13). 57 This is likely due to molecules showing a significantly lower mobility in solid film than in solution. Such behaviour results in only those excited molecules that are located at relatively close distance to a nearest neighbour being able to form bimolecular excited states, while molecules emitting unimolecular luminescence are "isolated", and in principle unable to come into contact with any of the other molecules.…”

“…[62][63][64][65] The OLED device structure used in this work is based on a previously reported architecture using a mCP:PO-T2T host (1,3bis(carbazol-9-yl)benzene and 2,4,6-tris [3-(diphenylphosphinyl)phenyl]-1,3,5-triazine, respectively) that was optimised for excimer-forming mono-Pt(II) complexes with pyridyltriazole ligands. 57 3. Devices 1 and 2 were produced with an emissive layer of 65 ± 5 nm thickness.…”

Highly Photoluminescent Blue Ionic Platinum-Based Emitters

“…20 Besides, it is worth to note that the CIE coordinates of devices based on 3A (0.22, 0.41) and 3B (0.24, 0.44) fit within the sky blue region, unlike others solution-processed platinum-based PhOLEDs reported up to now. 25,28,30,31,[34][35][36]39 Conclusions New Pt(II) compounds containing cyclometalated N-heterocyclic carbenes and chelate diphosphines, [Pt(R-C^C*)(P^P)]PF6 (R = H, NC; P^P = dppm, dppe, dppbz) were prepared from their corresponding complex, [{Pt(R-C^C*)(µ-Cl)}2]. The presence of two chelate ligands (C^C* and P^P) bestows great robustness and stability onto these complexes.…”

“…27 However, there are still limited examples, in particular for solution-processable OLEDs based on Pt(II) complexes. 25,26,[28][29][30][31][32][33][34][35][36][37][38][39][40] Within this perspective we decided to extend the family of [Pt(R-C^C*)(P^P)]PF6 compounds by changing the C^C* group. As result, herein we report the synthesis and the structural properties of compounds [Pt (R-C^C*)(P^P)]PF6 (R= H, P^P: dppm 1A, dppe 2A, dppbz 3A; R = CN, P^P: dppm 1B, dppe 2B, dppbz 3B).…”

Photophysics of TADF Guest–Host Systems: Introducing the Idea of Hosting Potential

“…Two classes of emitter materials, phosphorescent and thermally activated delayed fluorescence (TADF) materials, are playing an important role to harvest 100% of triplet states. 9 , 10 Phosphorescent materials containing heavy metals, such as platinum 11 , 12 and iridium, 13 creating strong spin–orbit coupling activate triplet state radiative decay. 14 On the other hand, TADF molecules convert triplet states into an emissive singlet state through thermal activation of a vibronically coupled spin–orbit mechanism given a small energy gap between triplet and singlet states (Δ E ST ) and a third state to mediate the exchange.…”