Conjugated polymers based on phenothiazine and fluorene in light-emitting diodes and field effect transistors

Poly[10-(2'-ethylhexyl)-phenothiazine-3,7-diyl] (PPTZ), Poly [9,9-bis(2'-ethylhexyl)fluorene-2,7-diyl] (PBEHF), and their random copolymers, poly(BEHF-co-PTZ), were synthesized through Ni(0)-mediated polymerization. Light-emitting devices were fabricated using these polymers in an ITO (indium tin oxide)/PEDOT:PSS/polymer/Ca/Al configuration. Each EL device constructed with a poly(BEHF-co-PTZ) copolymer exhibited significantly enhanced efficiency and brightness compared to devices constructed from the PPTZ and PBEHF homopolymers. The EL device constructed with poly(88BEHF-co-12PTZ) exhibited the highest power efficiency and brightness (4200 cd/m(2) and 2.08 cd/A respectively). This enhanced efficiency of the copolymer devices results from their improved hole injection and more efficient charge carrier balance, which arise due to the HOMO levels (similar to5.4 eV) of the poly(BEHF-co-PTZ) copolymers, which are lower than that of the PBEHF homopolymer (similar to5.8 eV). An organic field effect transistor was also fabricated using PPTZ as a new p-type channel material and characterized. The measured field effect mobility of the transistor was 0.8 x 10(-4) cm(2)/V(.)s and the on/off ratio of the device was similar to10(3).