New Molecular Design Concurrently Providing Superior Pure Blue, Thermally Activated Delayed Fluorescence and Optical Out-Coupling Efficiencies

Abstract

Simultaneous enhancement of out-coupling efficiency, internal quantum efficiency, and color purity in thermally activated delayed fluorescence (TADF) emitters is highly desired for the practical application of these materials. We designed and synthesized two isomeric TADF emitters, 2DPyM-mDTC and 3DPyM-pDTC, based on di(pyridinyl)methanone (DPyM) cores as the new electron-accepting units and di(tert-butyl)carbazole (DTC) as the electron-donating units. 3DPyM-pDTC, which is structurally nearly planar with a very small ΔE, shows higher color purity, horizontal ratio, and quantum yield than 2DPyM-mDTC, which has a more flexible structure. An electroluminescence device based on 3DPyM-pDTC as the dopant emitter can reach an extremely high external quantum efficiency of 31.9% with a pure blue emission. This work also demonstrates a way to design materials with a high portion of horizontal molecular orientation to realize a highly efficient pure-blue device based on TADF emitters.

High‐Performance Nondoped Blue Delayed Fluorescence Organic Light‐Emitting Diodes Featuring Low Driving Voltage and High Brightness

“…However, the sky-blue emission with CIEy > 0.3 is inadequate for the display applications. [5,8,[15][16][17][18][19][20][21][22][23][24][25][26] Therefore, it is highly desirable to further optimize molecular structures of blue TADF emitters to ameliorate the TADF behaviors in both doped and nondoped OLEDs. [32] In addition, most of high-efficiency blue TADF emitters reported to date can only function well in the doped thin films, and encounter the serious performance degradation in nondoped devices due to the aggregation-caused emission quenching (ACQ).…”

“…[8][9][10][11][12][13][14][15][16][17][18][19][20] The use of pure organic TADF emitters allows almost 100% internal electroluminescence (EL) quantum efficiency by harvesting the triplet excitons (T 1 ) to the emissive singlet excited states (S 1 ) via reverse intersystem crossing (RISC). [8][9][10][11][12][13][14][15][16][17][18][19][20] The use of pure organic TADF emitters allows almost 100% internal electroluminescence (EL) quantum efficiency by harvesting the triplet excitons (T 1 ) to the emissive singlet excited states (S 1 ) via reverse intersystem crossing (RISC).…”

“…

TADF) materials without using heavy metals have gained great attention as the third-generation organic light-emitting diode (OLED) emitters. [8][9][10][11][12][13][14][15][16][17][18][19][20] However, achieving high-performance deep blue TADF OLEDs is still challenging, since most of them suffer from poor color purity, low brightness, severe EL efficiency roll-off, as well as short operational stability. To date, high external quantum efficiency (EQE) exceeding 20% has been achieved for blue, green, and red TADF emitters in OLEDs.

…”

Combining Charge‐Transfer Pathways to Achieve Unique Thermally Activated Delayed Fluorescence Emitters for High‐Performance Solution‐Processed, Non‐doped Blue OLEDs

“…[1][2][3][4][5][6] Utilization of TADF emitters provide an opportunity not only to reduce the overreliance on expensive precious metals for efficient OLEDs, but also to solve the urgent issue of developing stable and efficient blue materials and their devices. [2][3][4][10][11][12][13] While great progress has been made,s ome key challenges remain to be tackled. [2][3][4][10][11][12][13] While great progress has been made,s ome key challenges remain to be tackled.…”

Recent progress of pyrimidine derivatives for high-performance organic light-emitting devices

“…[14][15][16][17][18][19][20][21][22][23][24][25] Until recently, several TADF OLEDs have achieved a high EQE of over 30% at maximum. [26][27][28][29][30][31][32] The efficiency of the TADF-based OLEDs is expected to exceed that of OLEDs based on phosphorescent emitters due to the unlimited molecular design of pyrimidine derivative-based TADF emitters.…”