The photophysical, electrochemical, and optoelectronic properties of conjugated systems incorporating dibenzophosphole or phosphole moieties are described. Dibenzophosphole derivatives are not suitable materials for OLEDs due to their weak photoluminescence (PL) in the solid state and the instability of the devices. Variation of the substitution pattern of phospholes and chemical modification of their P atoms afford thermally stable derivatives, which are photo- and electroluminescent. Comparison of the optical properties of solution and thin film of thioxophospholes shows that these compounds do not form aggregates in the solid state. This property, which is also supported by an X-ray diffraction study of three novel derivatives, results in an enhancement of the fluorescence quantum yields in the solid state. In contrast, (phosphole)gold(I) complexes exhibit a broad emission in thin film, which is due to the formation of aggregates. Single- and multilayer OLEDs using these P derivatives as the emissive layer have been fabricated. The emission color of these devices and their performances vary with the nature of the P material. Interestingly, di(2-thienyl)thiooxophosphole is an efficient host for the red dopant DCJTB, and devices using the gold complexes have broad emission spectra.

A series of organic dyes containing a phenothiazine central unit were synthesized and were used effectively in the fabrication of dye-sensitized solar cells (DSSCs). A cyanoacrylate moiety was added at the C(3) position of the phenothiazine as an electron acceptor, and a triarylamine moiety was attached at the C(7) position as an electron donor. The DSSCs made with these dyes displayed remarkable quantum efficiency, ranging from 4.2-6.2% under an AM 1.5 solar condition (100 mW cm À2 ). A variety of substituents, i.e., methyl, hexyl and triphenylamino groups, were added at the N(10) of phenothiazine in order to optimize the incident photon-to-current conversion efficiency. Along the main chromophore a thiophenylene group was inserted at different positions to examine its influence on the properties of devices. The best performance was found in compound NSPt-C6, in which a hexyl group was attached at the N(10) of phenothiazine and a thiophenylene at the C(7) position. It displayed a short-circuit current (J sc ) of 14.42 mA cm À2 , an open-circuit voltage (V oc ) of 0.69 V, and a fill factor (ff) of 0.63, corresponding to an overall conversion efficiency of 6.22%. Their photophysical properties were analyzed with the aid of a time-dependent density functional theory (TDDFT) model with the B3LYP functional. Their photovoltaic behavior was further elucidated by the electrochemical impedance spectroscopy.

A series of organic dyes containing oligo-phenothiazine were synthesized and used effectively on the fabrication of dye-sensitized solar cells (DSSCs). In these compounds the phenothiazine moiety functions both as an electron donor and as a p-bridge. These materials exhibit considerably high values of open-circuit voltage (V oc ) ranging from 0.78-0.83 V under an AM1.5 solar condition (100 mW cm À2 ). Two kinds of substituents, i.e., hexyl and hexyloxyphenyl groups, were added onto the N(10) of phenothiazine for comparison. The best device displayed a short-circuit current (J sc ) of 14.3 mA cm À2 , an open-circuit voltage (V oc ) of 0.83 V, a fill factor (FF) of 0.65, corresponding to an overall conversion efficiency of 7.78%. Their photophysical properties were analyzed with the aid of a time-dependent density functional theory (TDDFT) model with the B3LYP functional. The electronic nature of the devices was further elucidated by using electrochemical impedance spectroscopy.