This work reports the first structure-properties relationship study of ortho [2,1-c]-, meta [1,2-a]-, and para [1,2-b]dihydroindenofluorenes, highlighting the influence of bridge rigidification on the electronic properties. This study has made it possible to devise an extended π-conjugated molecule with both a high triplet state energy level and excellent thermal and morphological stability. As a proof of concept, dihydroindenofluorenes were used as the host in sky-blue phosphorescent organic light-emitting diodes (PhOLEDs) with high performance.

This work reports the use of 9,9′-spirobifluorene and 4-phenyl-9,9′-spirobifluorene, pure hydrocarbon small molecules, as hosts for efficient green and blue phosphorescent OLEDs.