Organic light-emitting diodes (OLEDs) have been successfully commercialized as a new generation displays. However, the OLEDs industry with a market of tens of billions of dollars still relies on inefficient deep-blue conventional fluorescent emitters . Blue phosphorescent (PhOLEDs) and thermally activated delayed fluorescent OLEDs (TADF-OLEDs) have long been regarded as promising alternatives to blue fluorescent OLEDs, due to their theoretical capacity for achieving near-unity internal quantum efficiency (IQE) . And recently significant advancements have been made in the development of stable luminescent blue materials , particularly platinum complexes following the initial work on PtON7-dtb . However, the device stability is still limited by the lack of a suitable host material, of which the progress lags behind and is even more challenging considering not only the required higher energy levels than the dopant but also balanced and good charge transfer . A breakthrough has recently been made by Sun and coworkers by developing a deep-blue exciplex-forming host (SiCzCz and SiTrzCz2) , based on which the deep-blue PhOLEDs achieved a long operational lifetime (LT70, where LTx indicates the time to reach x% of the initial luminance) of 1,113 h at an initial luminance of 1000 cd m -2 with a y coordinate of 0.197, representing one of the longest lifetimes for deep-blue devices. Following this pioneer work, successive works on deep-blue OLEDs relay on SiCzCz: SiTrzCz2 to provide decent device lifetimes, evidencing the great potential of this system . However, not only the stability but also the charge transport ability of SiCzCz: SiTrzCz2 still needs to be further improved as it always requires high device operation voltage. Improving the performances of SiCzCz: SiTrzCz2 therefore has been an exigent task, but facing formidable challenges.