Thermally Activated Delayed Fluorescence Sensitization for Highly Efficient Blue Fluorescent Emitters

Abstract

Hyperfluorescence is emerging as a powerful strategy to develop optoelectronic devices with high-color purity and enhanced stability. It requires appropriate integration of a sensitizer displaying efficient thermally activated delayed fluorescence (TADF) and an emitter displaying strong, narrowband fluorescence. Here, through a joint computational and experimental approach, an unprecedented, end-to-end systems level description of the electronic and optical processes that take place in a hyperfluorescent emissive layer composed of a TADF sensitizer, 2,5-bis(2,6-di(9H-carbazol-9-yl) phenyl)-1,3,4-oxadiazole (4CzDPO), and a fluorescent emitter, 2,5,8,11-tetratert-butylperylene (TBPe) is provided. The photophysical properties measurement of the emissive layer is combined with the computational determination of the electronic properties, film morphology, and excitation transfer phenomena. The Förster resonance energy transfer rates from 4CzDPO to TBPe are on the order of 10 11 s −1 , considerably higher than the radiative and nonradiative recombination rates for 4CzDPO. These features ensure nearly complete energy transfer to TBPe, leading to a five-fold increase in the photoluminescence quantum yields in the 4CzDPO:TBPe system in comparison to neat films of 4CzDPO. This approach highlights the factors that can provide efficient energy transfer from TADF molecules to fluorescent emitters, suppress energy transfer among TADF molecules, and avoid the need for a host material within the emissive layer.

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

“…Such devices have enhanced external quantum efficiency (EQE) of up to 19% and improved operational lifetime of up to T80 at 1000 cd m −2 ≈320 h (here, we refer to TX as the time during which the luminance decreases to X% of its initial luminance). [ 33 , 34 , 35 , 36 , 37 ] Deep blue hyper‐OLEDs incorporating multiple resonance fluorescent (MRF) emitters have been spotlighted, achieving superior luminescent properties such as high photoluminescence quantum yield (PLQY) of > 0.8, small Stokes shift (≈40 nm), and narrow full width at half maximum (FWHM) of < 30 nm. [ 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ] Particularly, a recent deep‐blue hyper‐OLED that employed a TADF sensitizer with a high reverse intersystem crossing rate (k RISC = 2.36 × 10 6 s −1 ) and an MRF emitter is noteworthy.…”

Pseudospectral implementations of long‐range corrected density functional theory

“…Table 3 shows the dimmer interaction energies calculated by CS and PS methods using CAM‐B3LYP‐D3 (CAM‐B3LYP with D3 dispersion correction 81 ) and ω B97X‐D ( ω B97X with D2 dispersion correction 25 ). The monomers used in this study are fluorescent materials or thermally activated delayed fluorescence (TADF) materials, and they are BPPyA, 82 DMAC‐DMT, 82 DBFPO, 82 DPEPO, 82 mCP, 83 ACRSA, 83 4CzDPO, 84 TBPe, 84 and CBP 85 . The dimmers are formed from the force field‐based MD simulations of the monomers, and the dimmer structures after MD simulations are not further optimized by QM optimization method with specific DFT functionals/basis sets since our goal here is to compare the PS method to the CS method.…”

Active Learning Accelerates Design and Optimization of Hole-Transporting Materials for Organic Electronics

“…Organic light-emitting diodes (OLEDs) have received significant attention as the most demanded forthcoming display and lighting technology because of their low cost, lightweight, low power consumption, high brightness, and high contrast ( Chen et al, 2018 ; Lee et al, 2019a ; Lee et al, 2019b ; Abroshan et al, 2020a ; Abroshan et al, 2020b ; Abroshan et al, 2020c ; Abroshan et al, 2020d ). Recent developments in OLEDs with flexible panels have opened a new avenue for innovative technologies to fabricate cost-effective large-area, wearables, foldable and shape-fitting displays ( Jeong et al, 2020 ; Song et al, 2020 ; Yoo et al, 2020 ).…”