N-type organic luminescent materials based on siloles with aggregation-enhanced emission

Abstract

Simplifying the configurations of organic light-emitting diodes (OLEDs) without sacrificing device performances is of high practical importance to shorten fabrication procedures and cut down cost. In view of this, organic active materials for OLEDs are anticipated to possess multiple functions, including high solid-state emission efficiency, efficient hole- and/ or electron transport ability, etc. To realize this purpose, we designed a series of bifunctional materials consisting of a silole core and electron-transporting functional groups, such as dimesitylboryl and diphenylphosphoryl groups. These silole derivatives show aggregation-enhanced emission (AEE) characteristics and afford high emission efficiencies in the solid films. The presence of these electron-withdrawing substituents lowers the LUMO energy levels as revealed by cyclic voltammetry, and allows for efficient electron transport ability of the luminogens. The double-layer OLEDs fabricated using these silole derivatives as light-emitting and electron-transporting layers simultaneously show good electroluminescence performances, which are almost equal to those of triple-layer OLEDs with an additional electrontransporting layer (TPBi), revealing that they are excellent n-type light emitters. These results demonstrate that the combination of AEE-active luminogens with charge transport groups at molecular level is a promising design for multifunctional solid-state light emitters.