Improved Efficiency and Lifetime of Deep‐Blue Hyperfluorescent Organic Light‐Emitting Diode using Pt(II) Complex as Phosphorescent Sensitizer

Abstract

Although the organic light‐emitting diode (OLED) has been successfully commercialized, the development of deep‐blue OLEDs with high efficiency and long lifetime remains a challenge. Here, a novel hyperfluorescent OLED that incorporates the Pt(II) complex (PtON7‐dtb) as a phosphorescent sensitizer and a hydrocarbon‐based and multiple resonance‐based fluorophore as an emitter (TBPDP and ν‐DABNA) in the device emissive layer (EML), is proposed. Such an EML system can promote efficient energy transfer from the triplet excited states of the sensitizer to the singlet excited states of the fluorophore, thus significantly improving the efficiency and lifetime of the device. As a result, a deep‐blue hyperfluorescent OLED using a multiple resonance‐based fluorophore (ν‐DABNA) with Commission Internationale de L'Eclairage chromaticity coordinate y below 0.1 is demonstrated, which attains a narrow full width at half maximum of ≈17 nm, fourfold increased maximum current efficiency of 48.9 cd A−1, and 19‐fold improved half‐lifetime of 253.8 h at 1000 cd m−2 compared to a conventional phosphorescent OLED. The findings can lead to better understanding of the hyperfluorescent OLEDs with high performance.

Dinuclear PtII Complexes with Strong Blue Phosphorescence for Operationally Stable Organic Light‐Emitting Diodes with EQE up to 23 % at 1000 cd m−2

“…[19] In particular, when incorporated with phosphorescent metal complexes or a thermally activated delayed fluorescence (TADF) sensitizer in a hyper-OLED, high efficiency (EQE max = 32.2 %), long lifetime (LT 50 = 156 h at 1000 cd m À 2 ), and narrow FWHM (20 nm) deep-blue OLEDs (CIE y = 0.14) could be realized simultaneously. [20] Thus, given the good spectral overlap between the emission spectrum of 5 and absorption spectrum of the MRF emitter, ν-DABNA (N 7 ,N 7 ,N 13 ,N 13 ,5,9,11,15-octaphenyl-5,9,11,15-tetrahydro-5,9,11,15-tetraaza-19b,20b-diboradinaphtho[3,2,1de:1',2',3'-jk]pentacene-7,13-diamine; Figure S36, Supporting Information), complex 5 may be useful as a sensitizer for the ν-DABNA emitter. We therefore performed photoluminescence decay measurements on mCBP film samples containing 1 wt % ν-DABNA, 10 wt % 5, and ν-DABNA:5 (1 wt %:10 wt % co-doping); the decay curves are presented in Figure S37 (Supporting Information).…”

A gold(iii)–TADF emitter as a sensitizer for high-color-purity and efficient deep-blue solution-processed OLEDs

“…34 Recent studies demonstrated that multi-resonance TADF emitters could replace conventional fluorescent dopants to attain high-performance blue-emitting PSF/TASF OLEDs fabricated by vacuum deposition. 35–39 Enlightened by these recent advances, the obstacles of poor solubility of multi-resonance TADF emitters and inefficient ET from the hosts to multi-resonance TADF emitters, which hamper the development of blue SP-OLEDs, could be overcome by incorporating TADF sensitizers in the emitting layers (EMLs) to develop TASF devices.…”

Triplet-to-singlet exciton transfer in hyperfluorescent OLED materials

“…Such apparent incompatibility between efficient TADF and efficient fluorescence has prompted the development of the socalled hyperfluorescent devices. [8][9][10][11][12] In this approach, both TADF molecules and fluorescent emitters are employed as dopants in a host matrix. The working principle is that after triplet excitons undergo rISC in the TADF molecules, the newly generated singlets may diffuse and transfer to a fluorescent emitter by means of Fo ¨rster resonance energy transfer (FRET).…”