Light-emitting properties of a germyl-substituted PPV derivative synthesized via a soluble precursor

Abstract

The synthesis of a novel germyl-substituted poly(p-phenylenevinylene) (PPV) derivative, poly(2-triethylgermyl-1,4-phenylenevinylene) (TEG-PPV), via a soluble precursor polymer is described for the first time. The light-emitting properties of TEG-PPV are compared with those of the silyl-substituted PPV homologue poly(2-trimethylsilyl-1,4-phenylenevinylene) (TMS-PPV). The precursor polymer is solution-processable. After carrying out thermal elimination on the precursor polymer film, the resulting fully conjugated polymer film was found to exhibit high thermal stability in air, and absorption that is shifted to the longer wavelength region owing to the extension of the π-conjugated system. TEG-PPV exhibits efficient green light emission; the maximum PL emission of a TEG-PPV thin film was found to be at 515 nm. The HOMO and LUMO energy levels were also determined using photo-emission spectroscopy. The estimated HOMO and LUMO levels of TEG-PPV are 5.70 and 3.30 eV respectively. Single layered EL devices using TEG-PPV and TMS-PPV were fabricated in the ITO/Polymer/LiF/Al configuration. The performance of the TEG-PPV EL device was found to be comparable to that of the TMS-PPV device.