Influence of molecular dipoles on the photoluminescence and electroluminescence of dipolar spirobifluorene

Abstract

Here we study a series of strongly fluorescent spirobifluorene compounds, red PhSPDCV and blue PhSPDPV, together with their spiro "dimer" analogs, BisPhSPDCV and blue BisPhSPDPV. We found that the fluorescence quantum yield as well as the OLED performance of the strongly dipolar red PhSPDCV decrease significantly in the "dimeric" analog BisPhSPDCV, but not in the weakly dipolar PhSPDPV and BisPhSPDPV. On the other hand, by doping the highly dipolar PhSPDCV to an isolated environment having low polarity Alq3 as the host matrix and avoiding the emission-quenching dipole from the neighboring molecules, very high performance of saturated yellow OLEDs has been obtained as well.