Electroluminescent properties of a novel σ*-π* conjugated polymer, poly[1,1-(2,3,4,5-tetraphenylsilole)]

The optical and electronic properties of a sigma*-pi* conjugated polymer, poly[1,1-(2,3,4,5-tetraphenylsilole)] (PTPS), have been studied. PTPS shows emissions of sigma*-pi and pi*-pi transitions at 356 and 520 nm, respectively. PTPS light-emitting diodes (LEDs) with a single layer structure emit green-yellow light, corresponding to the pi*-pi transition, with an external quantum efficiency of 3 x 10(-2)%. The effect of the doping of poly(methylphenylsilane) (PMPS), a good hole transport material, into PTPS has also been studied. The shapes of the photoluminescence spectra of PMPS:PTPS films are the same as those of a PTPS film, indicating efficient energy transfer from PMPS to PTPS. PTPS:PMPS LEDs emit essentially the same green-yellow light as PTPS LEDs and exhibit better device characteristics than those without PMPS, that is, smaller rum-on voltages, larger current densities, and larger external quantum efficiencies. The PMPS:PTPS (PMPS: 30 wt%) LEDs show a luminance of 27 cd/m(2) at a driving current density of 13 mA/cm(2).