Highly luminescent π-conjugated dithienometalloles: Photophysical properties and their application in organic light-emitting diodes

We have disclosed the photophysical and electroluminescent properties of a series of hetero-annulated π-conjugated dithieno[3,2-b:2′,3′-d] metallole derivatives incorporating Ge, Si, P, and S atoms as a bridging center. The influence of the hetero-annulated structures on their photophysical properties has been investigated systematically by UV/vis and photoluminescence (PL) spectroscopy, transient PL measurements, and DFT calculations. All these compounds show bright fluorescence with high quantum yields both in solutions and in doped thin films with a host matrix. Furthermore, the OLEDs employing the dithienometallole emitters exhibit high external quantum efficiencies of ∼6% at a practical brightness.