A Hot Exciton Luminogen Constructed by an o‐Carborane Scaffold

Abstract Emitters with the combination of an electron donor (D) and an acceptor (A) have been widely studied and usually exhibited interesting photophysical properties. Hot exciton materials involving an ordinary D‐A structure typically undergo a hybridized local charge transfer (HLCT) process. However, the hot exciton molecules containing more D/A fragments are much less explored. In this study, a new hot exciton material based on an inorganic boron cluster is designed and synthesized, which possesses a V‐type D–A–A′–D′ molecular architecture. The emitter shows an impressive photoluminescence quantum yield (PLQY) of up to 90% and demonstrates multiple emissions, excitation‐wavelength‐, solvent‐, and temperature‐dependent emissions. These characteristics are attributed to the coexistence of HLCT and the through‐space charge transfer process (TSTC) triggered by an o‐carborane scaffold in the excited state. Besides, the interchangeable HLCT/TSCT/hRISC processes are demonstrated by temperature‐dependent spectra and femtosecond time‐resolved transient absorption spectra. These findings confirm a novel hot exciton mechanism, simultaneously induced by HLCT and TSCT. This is also the first example of a carborane‐based hot exciton molecule. The current study not only reports a new molecular architecture for a hot exciton material but also gives rise to a new insight into the hot exciton mechanism.