Thermally stable fluorescent blue organic light-emitting diodes using spirobifluorene based anthracene host materials with different substitution position

Thermally stable blue organic light-emitting diodes (OLEDs) were developed using anthracene based host materials with a spirobifluorene group. 4-Bromospirobifluorene and 2-bromospirobifluorene were attached to the anthracene core and the effect of the substitution position on the physical properties and device performances of the blue fluorescent OLEDs was investigated. The 4-spirobifluorene substitution was better than the 2-spirobifluorene substitution in terms of thermal stability and widened the bandgap of the anthracene based host material due to the geometrical structure of the material. However, the wide bandgap of the host material with 4-spirobifluorene had negative effect on the current density and efficiency of the blue devices.