Two spiro[fluorene-9,8′-indolo[3,2,1-de]acridine] derivatives as host materials for green phosphorescent organic light-emitting diodes

Two host materials based on spiro[fluorene-9,8′-indolo[3,2,1- de ]acridine] derivatives were designed and synthesized by introducing the benzofuran/benzothiophene unit to the spiro [fluorene-9,8′-indolo[3,2,1- de ]acridine] unit. The two host materials exhibited high triplet energy level (>   2.65   eV) and the benzofuran-substituted derivative presented suitable glass transition temperature (>   130   °C). Their electrochemical and photo-physical properties were also determined. The green phosphorescent organic light-emitting diodes based on the two host materials obtained electroluminescence performances with external quantum efficiencies of 14.3   ±   0.1% and 11.9   ±   0.1%, respectively.