Multiple σ–π Conjugated Molecules with Selectively Enhanced Electrical Performance for Efficient Solution-Processed Blue Electrophosphorescence

Selectively and controllably regulating molecular functions of organic optoelectronic materials with high solubility for solution-processible devices is highly desired but remains as one of the most significant challenges in material science. Here, a concise molecular design strategy is reported to achieve effective electronic communications using efficient d-orbital participated σ–π conjugations between Si and π unit for purposely modulating the electrical properties of organic optoelectronic materials. Through a two-step reaction in high yield, DSiDCzSi with the enhanced σ–π conjugation is facilely constructed by introducing multiple triphenylsilanes into carbazole unit. Impressively, DSiDCzSi demonstrates a largely increased d-orbital participated extent of Si, which results in the selectively improved frontier orbital energy level, enhanced carrier injection and transportation ability, excellent solubility, and film-forming property. Using DSiDCzSi as a host matrix, solution-processed blue electrophosphorescence device exhibits a maximum external quantum efficiency up to 23.5%, which is among the best values of FIr6-based blue phosphorescent organic light-emitting diodes reported to date. This work, which reveals the vital role of d-orbital participated σ–π conjugations in solving the inherent interference between optical and electrical properties of π-conjugated materials, can provide an extensible and universal avenue for designing and constructing high-performance organic optoelectronic materials for advanced device applications.