Tetrasubstituted adamantane derivatives with arylamine groups: Solution-processable hole-transporting and host materials with high triplet energy and good thermal stability for organic light-emitting devices

•A series of adamantane derivatives as host materials were designed and synthesized.•The non-conjugated adamantane skeleton impart the materials with high triplet energy.•The OLEDs based on these materials realized high device efficiencies.

Four new host/hole-transporting materials, namely 4,4′,4″,4‴-(adamantane-1,3,5,7-tetrayl)tetrakis(N,N-diphenylaniline) (4TPA-Ad, 1),4,4′,4″,4‴-(adamantane-1,3,5,7-tetrayl)tetrakis(N,N-di-p-tolylaniline) (4MTPA-Ad, 2), 1,3,5,7-tetrakis(4-(9H-carbazol-9-yl)phenyl)adamantane (4Cz-Ad, 3) and 1,3,5,7-tetrakis(4-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)adamantane (4tBuCz-Ad, 4), were designed and synthesized by incorporating four electron-donating arylamine units into the rigid adamantane skeleton via a simple C–N coupling reaction. Their thermal, photophysical and electrochemical properties were investigated. The molecular design endows the materials with high triplet energies of ∼3.0 eV, good solution processability, high thermal stability and appropriate HOMO levels. Two types of electroluminescent devices using 1–4 as hole-transporting or host materials were fabricated. The device based on 2 as solution-processed hole-transporting material and tris(quinolin-8-yloxy)aluminum as an emitter revealed a maximum current efficiency of 4.2 cd A−1, which was comparable with the TAPC-based control device. The sky-blue device employing 2 as solution-processed host material and 4,6-(difluorophenyl)pyridine-N,C2′)picolinate (FIrpic) as an emitter showed a maximum current efficiency of 16.6 cd A−1 with Commission Internationale de I’Eclairage (CIE) coordinates of (0.16, 0.32).

Graphical abstractFour adamantane-based compounds with high triplet energy levels and good thermal properties are designed by incorporating four electron-donating arylamine units into the rigid adamantane skeleton. These compounds are demonstrated not only as excellent hole-transporting materials for solution-processed Alq3 emitting OLEDs, but also as good host materials for blue phosphorescent OLEDs.Figure optionsDownload full-size imageDownload as PowerPoint slide