Highly efficient and stable deep-blue organic light-emitting diode using phosphor-sensitized thermally activated delayed fluorescence

Abstract

Phosphorescent and thermally activated delayed fluorescence (TADF) blue organic light-emitting diodes (OLEDs) have been developed to overcome the low efficiency of fluorescent OLEDs. However, device instability, originating from triplet excitons and polarons, limits blue OLED applications. Here, we develop a phosphor-sensitized TADF emission system with TADF emitters to achieve high efficiency and long operational lifetime. Peripheral carbazole moieties are introduced in conventional multi-resonance–type emitters containing one boron atom. The triplet exciton density of the TADF emitter is reduced by facilitating reverse intersystem crossing, and the Förster resonant energy transfer rate from phosphor sensitizer is enhanced by high absorption coefficient of the emitters. The emitter exhibited an operational lifetime of 72.9 hours with Commission Internationale de L’Eclairage chromaticity coordinate y = 0.165, which was 6.6 times longer than those of devices using conventional TADF emitters.

49‐3: Invited Paper: Tetradentate Pt Complexes for Efficient and Stable Blue OLEDs

“…In summary, we developed an aqua blue OLED with a peak EQE of 17.6% and an estimated LT90 of 580.7 hours at 1000 cd m -2 . The color quality of blue PhOLED can be further improved by employing previously reported phosphorescence sensitized fluorescence strategy [15][17] [18]. Our results demonstrate that the tetradentate Pt(II) complexes can be a viable solution to produce efficient and long-lasting blue OLEDs in the future.…”

Precise modulation of multiple resonance emitters toward efficient electroluminescence with pure-red gamut for high-definition displays

“…The sensitized emission process entailed the efficient harvesting of triplet excitons generated by the sensitizer and their subsequent transfer to the dopants, as detailed in fig. S32 and the “Discussion for energy transfer process” section in the Supplementary Materials ( 36 , 53 ). With a low dopant concentration of 1 wt % for the emitter, Dexter energy transfer was unfavored, and the Förster resonance energy transfer (FRET) could be regarded as the dominant process in our sensitized system ( 54 , 55 ).…”

“…Last, the EL operation stability of the encapsulated pure-red device using CzIDBNO was assessed at an initial luminance ( L 0 ) of 1000 cd m −2 . The device demonstrated a long T 98 (time to lose 2% of the initial luminance) of 297 hours, attributed to the good stability of the emitter, balanced charge-carrier transport, and fast exciton usage by the FRET process ( 53 , 57 ). On the basis of the excellent alignment of the lifetime data with the stretched exponential decay model (fig.…”

Sensitized organic light-emitting diodes: towards high efficiency and long lifetimes

“…Chu et al designed two new MR-TADF materials, TBE01, and TBE02, by adding a carbazole group to the periphery of t -DABNA. 39 The materials exhibited a high molar extinction coefficient, a fast RISC rate, and weak hole-trapping characteristics. PtON-TBBI exhibiting suitable photocharacteristics and excellent stability was used as a phosphorescent sensitizer.…”