Peripheral engineering of platinum(ii) dicarbene pincer complexes for efficient blue hyperphosphorescent organic light-emitting diodes

Pt(ii) dicarbene pincer complexes have been explored as deep-blue phosphors with narrowband emissions. Generally, they form excimers easily and their relatively long emission lifetimes also limit their applications as OLED emitters. Herein, we developed a simple method to modify 1,3-bisimidazol-3-ium pro-chelates and obtained three Pt(ii) dicarbene pincer complexes, thus studying the issue of excimer formation vs. peripheral appendages. As a result, blue emissions can be maintained at doping concentrations of up to 20 wt% for IPrtBuPt. Moreover, the emission of IPrtBuPt was found to significantly overlap with the absorption of nu-DABNA, an efficient blue boron/nitrogen based multi-resonant TADF molecule. A hyper-OLED using IPrtBuPt as a sensitizer and nu-DABNA as a terminal emitter achieved EQEs of up to 33.59%, FWHM of 20 nm and CIE coordinates of (0.124, 0.148). These results demonstrated a successful example of utilizing both structural engineering and smart device architecture for getting efficient blue devices with suppressed efficient roll-off.