Spirobicyclic host material with pseudo-intramolecular charge transfer: Improving color purity of high-performance pure-blue and white thermally activated delayed fluorescence diodes

An asymmetrical host as phosphine oxide group-distorted spirobixanthene was developed with the features of ambipolar property, low polarities and limited intermolecular interactions to realize highly efficient pure-blue and white thermally activated delayed fluorescence (TADF) diodes, providing a new way to overcome the bottleneck in color purity.