Blue-emitting organic electrofluorescence materials: progress and prospective

Abstract

The recent progress in blue-emitting organic electrofluorescence materials with high performance using triplet excitons is reviewed.

Triplet fusion delayed fluorescence materials for OLEDs

“…For example, a non-doped deep-blue OLED with 7 as the EML was found to show relatively high performance [EQE of 4.61% and LE of 3.64 cd A -1 at 10 mA cm -2 ; CIE1931: (0.151, 0.086)] [38]. Lee et al [39] attributed the satisfactory EL performance of 7 to the presence of TTA processes. Suzuki [40] reported another anthracene derivative 8, blue OLED using it as the host material shows an EQE max of as high as 11.9%.…”

Thieno[3,4-c]pyrrole-4,6-dione as novel building block for host materials for red PhOLEDs

“…[3][4][5][6][7][8] The application of transition metal emitters in phosphorescent OLEDs (PhOLEDs) 9,10 and of organic compounds capable of thermally activated delayed fluorescence (TADF) 11 boosted the efficiency of OLED devices. [12][13][14][15][16] Therefore, one major goal of research is the development of new host materials for these emitters. [17][18][19][20][21] In particular, the application of bipolar host materials consisting of donor and acceptor subunits proved successful, owing to their balanced charge transport properties and thus simplified device structures and broad recombination zones.…”

Quantitative analyses of high electroluminescence efficiency of thermally activated delayed fluorescence emitters based on acridine–triazine hybrids

“…[1][2][3][4][5][6][7][8] Since the pioneering introduction of thermally activated delayed fluorescence (TADF) emitters in OLEDs by Uoyama et al, 2 TADF materials have attracted intensive research in the past few years. This is mainly due to the capability of TADF materials in harvesting triplet excitons by the thermally activated upconversion and in giving possible 100% internal quantum efficiency in electroluminescence (EL), through purely organic molecular frameworks and without the need to incorporate transition metals like in phosphorescent emitters.…”

“…This is mainly due to the capability of TADF materials in harvesting triplet excitons by the thermally activated upconversion and in giving possible 100% internal quantum efficiency in electroluminescence (EL), through purely organic molecular frameworks and without the need to incorporate transition metals like in phosphorescent emitters. [1][2][3][4][5][6][7][8] In TADF molecules, through reducing the spatial overlap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, the energy gap (ΔE ST ) between the lowest excited singlet (S 1 ) and triplet (T 1 ) states can be effectively reduced to facilitate efficient upconversion of T 1 excitons to S 1 . 2,[5][6][7][8] On the other hand, the optical outcoupling is also a critical issue for enhancing the overall external quantum efficiency (EQE) of OLEDs for practical use.…”

“…[1][2][3][4][5][6][7][8] In TADF molecules, through reducing the spatial overlap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, the energy gap (ΔE ST ) between the lowest excited singlet (S 1 ) and triplet (T 1 ) states can be effectively reduced to facilitate efficient upconversion of T 1 excitons to S 1 . 2,[5][6][7][8] On the other hand, the optical outcoupling is also a critical issue for enhancing the overall external quantum efficiency (EQE) of OLEDs for practical use. 9,10 In addition to many other optical approaches and structures, [11][12][13][14][15] reports in recent years have revealed the importance of the emitting dipole orientations of OLED emitters relative to the device plane.…”