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Tin-based alternating copolymers with a uniform π-conjugated segment were synthesized using the Heck reaction between distyrylstannane monomer and various difunctionalized monomers. The UV−vis absorption maximum peaks of the resulting polymers in chloroform solution and in thin films appeared in the wavelength range of 347−394 nm. Upon photoexcitation with light of wavelength 350 nm, their photoluminescence spectra exhibited an emissive maximum peak around 470−502 nm, corresponding to blue light emission. Multilayered light-emitting diodes with ITO/PEDOT (50 nm)/polymer (80 nm)/Ca (50 nm)/Al (200 nm) composition were fabricated. These LED devices exhibited an emissive maximum peak in the range of 464−472 nm. All of the materials exhibited a very low turn-on voltage of less than 4 V. From cyclic voltammetric studies and optical data, the LUMO level is estimated to be 3.20 eV for SnPhFPV and 2.90 eV for SnPhPVK, and the ionization potentials (HOMO level) were estimated to be 5.90 eV for SnPhFPV and 5.60 eV for SnPhPVK. This lowered LUMO level, in comparison to those of poly(p-phenylene) derivatives (such as PPP, ladderlike PPP, and PAF), reduces the energy barrier to electron injection, resulting in a lowering of the operating voltage in the polymeric LED. Compared to devices based on the tin-based polymers alone, devices based on blends between the tin-based polymers and PVK showed improved efficiency of power and luminescence by at least 2−4 times and 3−6 times, respectively. Also for these polymer:PVK blends, the electroluminescence efficiency enhances up to the range of 0.1−0.3 lm/W, and the purity of the emitted blue color improves. These results may be attributed to the intramolecular confinement by diluting the EL polymers with PVK. One of the devices based on a blend system between a tin-based polymer and PVK has a brightness of 2047 cd/m² at 11 V with a power efficiency of 0.3 cd/A.

Silicon-based alternating copolymers containing both electron-transport oxadiazole and hole-transport carbazole moieties in the main chain (SiHMOXD/Cz 10−01) were synthesized by means of the Heck coupling reaction. The resulting polymers exhibit a strong UV−visible absorption band in the range of 345−356 nm in chloroform solution and in film state. Their PL spectra show a maximum band around 435−485 nm in the blue region. The light-emitting diodes of Al (200 nm)/Ca (50 nm)/EL polymer (80 nm)/PEDOT (50 nm)/ITO were successfully fabricated. And, J−V curves show a turn-on voltage of 6−7 V. Their EL properties depend strongly on both the applied voltage and the loading amount of hole-transport carbazole moieties in the present copolymers. With the applied voltage, these emissive EL bands were red-shifted from blue region to red region. Also, the intensity of a blue EL band at the relatively high operating voltages increases with the loading amount of carbazole units. The LED device with the copolymer of SiHMOXD/Cz 19 exhibits the almost same intensity of two bands, like two crests, giving a strong white color. The blue EL color comes from the carbazole units in these silicon-based copolymers. The latter red EL color comes from a specific charge complex with oxadiazole (and carbazole moieties). The new red band is exhibited only in EL but not in PL spectra. The EL device based on SiHMOXD/Cz 19 has a luminescence efficiency of 0.052 lm/W and a power efficiency of 0.13 cd/A at an applied voltage of 9 V. And, the maximum luminance of the white emissive color was 6.04 cd/m² at an applied voltage of 17 V. In this paper, from the photophysical studies, a specific intramolecular charge complex was proposed.