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

The optical and electronic properties of a sigma*-pi* conjugated polymer, p oly[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, respective ly. PTPS light-emitting diodes (LEDs) with a single layer structure emit gr een-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(methylp henylsilane) (PMPS), a good hole transport material, into PTPS has also bee n studied. The shapes of the photoluminescence spectra of PMPS:PTPS films a re the same as those of a PTPS film, indicating efficient energy transfer f rom PMPS to PTPS. PTPS:PMPS LEDs emit essentially the same green-yellow lig ht as PTPS LEDs and exhibit better device characteristics than those withou t PMPS, that is, smaller rum-on voltages, larger current densities, and lar ger 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).