Ultrapure Blue Phosphorescent Organic Light-Emitting Diodes Employing a Twisted Pt(II) Complex

Abstract

Described herein is a stable complex, Pt(mpzpyOczpy-mesi), embodying efficient, narrow blue emission. The highly twisted structure of the complex improves the stability and efficiency of photo-and electroluminescence by reducing the intermolecular interactions. The complex in solution shows high photoluminescence efficiency (>95%) and radiative decay rate (K r = 2.9 × 10 5 s −1 ) with a narrow emission spectrum. The bottom-emitting phosphorescent device, BE1, exhibits durable deep blue emission with CIE coordinates of (0.145, 0.166) and 5.2 h of LT 50 at an initial luminance of 685 cd/m 2 . Top-emitting devices, TE1 and TE2, achieve ultrapure blue color with CIE x,y values of (0.141, 0.068) and (0.140, 0.071), respectively. TE4 shows high brightness of 3405 cd m −2 at 50 mA m −2 , EQE of 10.2% at 1000 cd/m 2 , and almost negligible color deviation around (0.135, 0.096) at viewing angles of 0°−60°.

Tetradentate Pt(II) Complexes with Peripheral Hindrances for Highly Efficient Solution-Processed Blue Phosphorescent OLEDs

“…The E HOMO / E LUMO value of the two complexes, estimated from their redox potentials measured by cyclic voltammograms with the ferrocene/ferrocenium couple as an internal reference (Figure S4), approach at −5.4/–2.3 eV and are also close to that of their analogues with the same mother coordinating structure, indicating the absence of influence by the nonactive peripheral substituents (Table ). , DFT calculations show more details of their frontier molecular orbitals (FMOs) (Figure S5). The LUMOs primarily correspond to the π* orbitals of pzpy and py2, whereas the HOMOs are composed of the d orbital of Pt, π orbitals of py1 and carbazolyl (cz), and the p orbital of the oxygen bridge.…”

“…Recently, our group reported a series of highly efficient complexes coordinated by pyrazolyl-pyridinyl (pzpy) tetradentate ligands (Chart ). , Pt­(pzpyOczpy- i Pr), bearing iso -propyl on the ortho position of the N py1 atom, exhibits tunable FWHMs from 40 to 149 nm due to the monomeric and excimeric broadening effect synchronizing with the doping concentration in the solid state. Spectra-stable deep-blue and white OLEDs were fabricated by employing 2 and 50 wt % complexes in the emissive layers, respectively.…”

“…By enhancing the structural twisting, Pt­(mpzpyOczpy-mesi) was designed for a pure-blue emitter due to the suppression of the spectral broadening effect. The devices employing Pt­(mpzpyOczpy-mesi) achieved high blue color luminescence of 1385 and 3405 cd/m 2 with CIE coordinates of (0.141, 0.068) and (0.135, 0.096), respectively . In this work, we address two complexes, Pt­(pzpyOczpy-B1) and Pt­(pzpyOczpy-B2), with peripheral bulky-group hindrances spatially connected to the chelating ligand core and investigate the hindering effect of substituents for the luminescent properties.…”

“…The devices employing Pt(mpzpyOczpymesi) achieved high blue color luminescence of 1385 and 3405 cd/m 2 with CIE coordinates of (0.141, 0.068) and (0.135, 0.096), respectively. 24 In this work, we address two complexes, Pt(pzpyOczpy-B1) and Pt(pzpyOczpy-B2), with peripheral bulky-group hindrances spatially connected to the chelating ligand core and investigate the hindering effect of substituents for the luminescent properties. The podlike alkyl groups are expected to eliminate the excimeric emission from the π−π interaction of pzpy moieties.…”

Cavity-Suppressing Electrode Integrated with Multi-Quantum Well Emitter: A Universal Approach Toward High-Performance Blue TADF Top Emission OLED

“…The TADF-TEOLEDs fabricated using seven QWs and the optimized CSE exhibit outstanding performance with high color purity, bright luminescence, an EQE of approximately 18.05%, lower angular dependence, and ~ 35% lower efficiency roll-off at 1000 cd m −2 compared to the control TEOLEDs. These device performances are superior to those of blue OLEDs reported in recent years [ 3 , 34 , 35 ], which are attributed to the synergetic amalgamation of the CSE that improves the angular dependency and the MQW EML that improves the color purity and efficiency roll-off.…”