In the presented work the electron accepting thieno[3,4-c]pyrrole-4,6-dione is introduced as a novel building block for donor–acceptor based host materials for Phosphorescent Organic Light Emitting Diodes (PhOLEDs). A series of three regioisomers consisting of the thieno[3,4-c]pyrrole-4,6-dione acceptor and carbazole donors linked via a phenylene linker was prepared and the impact of the phenylene substitution pattern on the molecular properties was analyzed. Regarding their applicability as host materials, the newly developed materials were investigated in red PhOLED devices achieving a high current efficiency of 30.6 cd A−1 corresponding to an external quantum efficiency of 17.7% and a high power efficiency of 23.8 lm W−1. Thus, we present the first successful application of the thieno[3,4-c]pyrrole-4,6-dione building block in host materials for PhOLEDs.

In the presented work click chemistry is utilized to introduce 1,2,3-triazoles as a functional linker in organic donor–acceptor materials. A systematic series of materials was prepared and characterized to investigate the effect of the linkage mode on the molecular properties. The 1,2,3-triazole linker allowed control of the degree of intramolecular charge transfer over a wide range depending on the substitution pattern of the triazole moiety. The prepared materials were successfully employed as host materials for green and red dopants in phosphorescent organic light emitting diodes. Thus, this work presents the first application of this novel linkage mode in the design and synthesis of functional π-conjugated organic donor–acceptor materials and their application in organic light emitting diodes.

•Planarization strategy towards CPB based materials applied.•Significantly improved thermal stabilities and triplet energies observed.•Green and blue PhOLED devices with low efficiency roll-off fabricated.•Blue PhOLEDs with high PE of 26.1 lm W−1 realized.•Indolo[3,2,1-jk]carbazole as building block for organic electronics established.Three novel planarized CPB derivatives (ICzCz, ICzPCz, ICzICz) have been synthesized and characterized concerning applications as host materials for PhOLEDs. The incorporation of fully planar indolo[3,2,1-jk]carbazole (ICz) in the CBP scaffold has been systematically investigated, revealing a significant impact on molecular properties, such as improved thermal stability (tg > 110 °C), high triplet energies (ET > 2.81 eV) and charge transport properties. Employing the newly developed materials as host materials, efficient green PhOLEDs (CEmax: 60.1 cd A−1, PEmax: 42.1 lm W−1, EQEmax: 15.9%) with a remarkably low efficiency roll-off of 5% at 1000 cd m−2 as well as blue PhOLEDs (ICzCz) with a high PE of 26.1 lm W−1 have been realized. Hence, the first comprehensive report on the application of ICz as integral building block for electroluminescent materials is presented, establishing this particular structural motive as versatile structural motive in this field.

A novel electron-transporting moiety, 1,2,4-thiadiazole, was first introduced to construct bipolar host molecules for phosphorescent organic light-emitting diodes (PhOLEDs). By incorporating 1,2,4-thiadiazole with typical hole-transporting carbazole moieties, a series of thiadiazole/carbazole hybrids, o-CzTHZ, m-CzTHZ, and p-CzTHZ, were synthesized. All the hybrids exhibit very high glass transition temperatures (Tg ≥ 167 °C) and show good thermal and morphological stability in films. Moreover, these host materials possess good bipolar charge transporting properties; electron and hole mobilities of these bipolar thiadiazole/carbazole hybrids can be tuned by simply adjusting the linkage modes between thiadiazole and carbazole moieties. The maximum external quantum efficiencies (ηEQE, max) in the green PhOLEDs with o-CzTHZ, m-CzTHZ, and p-CzTHZ as the hosts reached 26.1%, 24.0%, and 22.9%, respectively, and their EQE were still over 20% even at the high luminance of 10,000 cd/m2. This study demonstrates that 1,2,4-thiadiazole should be an excellent electron-transporting unit for bipolar phosphorescent hosts.

A new simple carbazole-N-benzimidazole bipolar luminogen mNBICz was constructed and utilized as a host for an FIrpic-doped blue device, and exhibited high efficiencies with a ηEQE,max of 26.2%, a ηC,max of 54.5 cd A−1 and a ηP,max of 52.2 lm W−1. Furthermore, a two-color, all-phosphor single layer white device displayed a ηEQE,max of 22.9%, a ηC,max of 62.5 cd A−1 and a ηP,max of 60.4 lm W−1.

In the presented work the electron accepting thieno[3,4-c]pyrrole-4,6-dione is introduced as a novel building block for donor–acceptor based host materials for Phosphorescent Organic Light Emitting Diodes (PhOLEDs). A series of three regioisomers consisting of the thieno[3,4-c]pyrrole-4,6-dione acceptor and carbazole donors linked via a phenylene linker was prepared and the impact of the phenylene substitution pattern on the molecular properties was analyzed. Regarding their applicability as host materials, the newly developed materials were investigated in red PhOLED devices achieving a high current efficiency of 30.6 cd A−1 corresponding to an external quantum efficiency of 17.7% and a high power efficiency of 23.8 lm W−1. Thus, we present the first successful application of the thieno[3,4-c]pyrrole-4,6-dione building block in host materials for PhOLEDs.

A new simple carbazole-N-benzimidazole bipolar luminogen mNBICz was constructed and utilized as a host for an FIrpic-doped blue device, and exhibited high efficiencies with a ηEQE,max of 26.2%, a ηC,max of 54.5 cd A−1 and a ηP,max of 52.2 lm W−1. Furthermore, a two-color, all-phosphor single layer white device displayed a ηEQE,max of 22.9%, a ηC,max of 62.5 cd A−1 and a ηP,max of 60.4 lm W−1.