Aggregation Dependent S1 and S2 Dual Emissions of Thiophene−Acrylonitrile−Carbazole Oligomer

Dual emissions from S1 (blue region) and S2 (UV region) states of a chromophore with donor−acceptor structure were observed at room temperature. The photophysical properties of the chromophore depend critically on the packing of the molecules. The molecule exhibits weak S1 emission and strong S2 emission; however, when it undergoes solid aggregation, the S1 emission is enhanced while the S2 emission is quenched. The H-packing (face-to-face packing) of the molecules is revealed as the key factor for this interesting aggregation-dependent dual emission.