A family of electroluminescent silyl-substituted poly(p-phenylenevinylene)s:: Synthesis, characterization, and structure-property relationships

A series of intense photoluminescent (PL) polymers containing silyl groups with chain length from C1 to C18 has been successfully synthesized through polycondensation reaction. Introducing silyl groups into a conjugated polymer affords the polymer good processability, amorphousness, good film-forming ability, and sharp emission. A systematic analysis of this series of polymers indicates that increasing the side chain length of the polymers will slightly lower the thermal stability while increasing the molecular weight. W-vis absorption and PL emission spectra of the polymers are quite similar. Cyclic voltammetric (CV) investigation of the polymers reveals that the side chain length plays an important role in the redox behavior of the polymers. Shorter side chain polymers possess better reproducibility of CV scans and higher peak currents, which implies that the chemical/electrical stability and charge injection and/or transporting ability for shorter side chain polymers are better than those for longer ones. Devices fabricated from poly[2,5-bis(decyldimethylsilyl)-1,4-phenylenevinylene] (DS-PPV) with the configuration of ITO/DS-PPV/Mg:Ag and ITO/PEDOT:PSS/DS-PPV/Mg:Ag indicate that the hole injection is the determining factor for device performance. Addition of the hole injection layer can improve the current efficiency and power efficiency by about 7 times and lower the turn-on voltage from 7.5 to 4.0 V for the two types of devices.