Synthesis and Characterization of Phosphine/Borane-Terminated Poly(silole-co-germole) for the Evaluation of Luminescent Polymer Light-Emitting Diode

Codehydrocoupling (using Red-Al) followed by borane/phosphine-capping (with Ph₂BCl and Ph₂PCl) of 1,1-dihydrotetraphenylsilole (1) and 1,1-dihydrotetraphenylgermole (2) (9:1 mole ratio) gave electroluminescent poly(silole-co-germole)s containing borane/phosphine-ends (3, 4) in high yield. The borane-terminated copolymer 3 emits at 522 nm and are electroluminescent at 521 nm. The fluorescence quantum yield of 3 in toluene is (1.60±0.30)×10⁻². The phosphine-terminated copolymer 4 emits at 520 nm and are electroluminescent at 520 nm. The fluorescence quantum yield of 4 in toluene is (1.60±0.20)×10⁻². 3 and 4 were then mixed in 1:1 ratio. The emission color of 3/4 mixture is green and the maximum brightness of the device is 2,760 cd/m² with a luminous efficiency of 0.67 lm/W. The borane/phosphine end groups in the 1:1 mixture of 3 and 4 exhibited no appreciable effect on the luminescent properties in spite of possible B—P dative bonding. Ge-132 helped to increase the B—P dative bonding. The electroluminescent copolymers 3 and 4 are good candidates for PLED (polymer light-emitting diode) fabrication.