A new series of copolymers (PSiFF) based on 3,6-silafluorene and 2,7-fluorene were synthesized via the Suzuki polycondensation. The influences of the 3,6-silafluorene content in the copolymers on the thermal, photophysical, electroluminescence and electrochemical properties were investigated. The incorporation of 3,6-silafluorene into the polyfluorene main chain not only suppressed the long-wavelength emission but significantly improved the efficiency and color purity of the copolymer-based devices. Both fluorene and 3,6-silafluorene took part in π-conjugation of the main chain and the electroluminescence spectra were remarkably blue-shifted with increasing wide bandgap 3,6-silafluorene content. The device based on PSiFF90 with the configuration of ITO/PEDOT : PSS/PVK/polymer/Ba/Al showed a quantum efficiency of 3.34% and a luminous efficiency of 2.02 cd A⁻¹ at a brightness of 326 cd m⁻² with CIE 1931 chromaticity coordinates of (0.16, 0.07), which almost match the NTSC standard blue pixel coordinates of (0.14, 0.08). Moreover, the incorporation of 3,6-silafluorene into the polyfluorene main chain significantly improved the spectral stability at annealing. The results indicate poly(3,6-silafluorene-co-2,7-fluorene) could be a promising candidate for blue-emitting polymers of high efficiency and good color purity.

An ultraviolet-emitting conjugated polymer, poly(9,9′-alkyl-3,6-silafluorene) with a wide band gap of 4.0 eV, has been synthesized and characterized.

Alternating triphenylamine-based copolymers poly[N-(4-sulfonatobutyloxyphenyl)-4,4′-diphenylamine-alt-1,4-phenylene] sodium salt (PTPOBS) and poly[N-(4-sulfonatophenyl)-4,4′-diphenylamine-alt-N-(p-trifluoromethyl)phenyl-4,4′-diphenylamine] sodium salt (PTFTS) were synthesized via palladium-catalyzed Suzuki coupling reaction. These polymers are soluble only in polar solvents, such as dimethyl sulfoxide (DMSO) and a mixed solvent of methanol and N,N-dimethyl formamide (DMF), rather than in non-polar solvents such as toluene and xylene. The electrochemical and photophysical properties of the resulted copolymers were investigated. The HOMO levels of the polymers (−5.08 eV for PTPOBS and −5.24 eV for PTFTS) were close to the work function of PEDOT. The relatively high-lying LUMO levels (−2.21 eV for PTPOBS and −2.24 eV for PTFTS) revealed that they had good electron-blocking capabilities. Devices with a PTPOBS or PTFTS layer inserted between ITO or PEDOT and of red and green-emitting polymers showed lower turn-on voltages and enhanced efficiency compared with the reference devices composed of bare ITO or ITO/PEDOT as anode. These polymers can be used as an independent hole-transport/electron-blocking layer or in combination with a PEDOT layer for fabrication of multilayer devices without intermixing with the subsequent EL layer by solution processing in full-color display applications.