Saturated and efficient red light-emitting fluorene-based alternating polymers containing phenothiazine derivatives

Abstract

A series of novel organic semiconducting polymers composed of fluorene and bis(2-phenyl-2cyanovinyl)-10-hexylphenothiazine) (PZB) comonomer were synthesized and characterized. These polymers were found to be thermally stable and readily soluble in common organic solvents. Our results showed that the color of the light emitted by the homopolymer, poly(9,9-dioctylfluorene-2,7-diyl) (PDOF), could be easily tuned by incorporating PZB comonomer, which has a narrower band gap. The photoluminescence (PL) emission spectra of the copolymers were highly red-shifted as the fraction of PZB in the copolymer was increased. Light-emitting devices were fabricated in the ITO/PEDOT:PSS/polymer/Ca/Al configuration using the polymers as the emitting layer. The electroluminescence (EL) device based on PF-PZB50 showed almost pure red emission [CIE coordinate values (x, y) - (0.63, 0.36)] that was very close to the standard red (0.66, 0.34) demanded by the National Television System Committee. In addition, bulk heterojunction polymeric photovoltaic cells (PPVCs) fabricated from a thin film composed of a blend of PF-PZB50 and the fullerene derivative [6,6]-phenyl C61 butyric acid methyl ester (PCBM), in a ITO/PEDOT:PSS/(PF-PZB50:PCBM = 1:3)/LiF/Al configuration, showed promising performance. Specifically, under 100 mW/cm(2) of AM 1.5 white light illumination, the device produced an open-circuit voltage of 0.78 V and a short-circuit current of 2.38 mA/m(2). The fill factor of the device was 0.29, and the power conversion efficiency was 0.53%.