No abstract

The synthesis, characterization, and photophysics of a series of solution-processable and strongly visible-light absorbing platinum(II) polyynes containing bithiazole-oligo(thienyl) rings were presented. Tuning the polymer solar cell efficiency, as well as optical and charge transport properties, in soluble, low-band gap PtII-based conjugated poly(heteroaryleneethynylene)s using the number of oligothienyl rings is described. These materials are highly soluble in polar organic solvents due to the presence of solubilizing bithiazole moieties and show strong absorptions in the solar spectra, rendering them excellent candidates for bulk heterojunction polymer solar cells. Their photovoltaic responses and power conversion efficiencies (PCEs) depend to a large extent on the number of thienyl rings along the main chain, and some of them can be used to fabricate highly efficient solar cells with PCEs of up to 2.7% and a peak external quantum efficiency to 83% under AM1.5 simulated solar illumination, which is comparable to that of poly(3-hexylthiophene)-based devices fabricated without additional processing (annealing or TiO(x) layer). The influence of the number of thienyl rings and the metal group on the performance parameters and optimization of solar cell efficiency was evaluated and discussed in detail. At the same blend ratio of 1:4, the light-harvesting ability and PCE increase sharply as the thienyl chain length increases. The present work provides an attractive approach to developing conjugated metallopolymers offering broad solar absorptions and tunable solar cell efficiency and demonstrates the potential of metalated conjugated polymers for efficient power generation.

The synthesis and structural, photophysical, electrochemical, and electroluminescent properties of a novel class of trifunctional Pt(II) cyclometalated complexes are reported in which the hole-transporting triarylamine, electron-transporting oxadiazole, and electroluminescent metal components are integrated into a single molecule. These neutral metal chelates display good thermal stability (>250 degrees C under N2) and morphological stability. All of them exhibit intense ligand-centered fluorescence and phosphorescence in fluid solutions at room temperature, but the emission spectra become largely dominated by triplet emission bands in CH2Cl2 glass at 77 K. Substituents with different electronic properties were introduced into the bipolar cyclometalating ligands to fine-tune the absorption and emissive characteristics of the compounds, and the results were correlated with theoretical calculations using density functional theory. A comparison of the photophysics and electrochemistry of our multifunctional systems to those only derived from each of the constituent components was also made and discussed. These Pt complexes can be vacuum-sublimed and applied as emissive dopants for the fabrication of vapor-deposited electrophosphorescent organic light-emitting devices (OLEDs), which generally exhibit good device performance with efficiencies up to 3.6%, 11.0 cd A-1, and 5.8 lm W-1. While the electroluminescence energy resembles that recorded in fluid solutions for these Pt emitters, these monochromatic OLEDs can emit tunable colors by varying the aryl ring substituents and the level of doping. Saliently, single dopant white-light electroluminescence, triggered by the simultaneous fluorescence/phosphorescence emission of the metal complexes and a variation of applied driving voltages, has also been realized based on some of these multifunctional complexes with peak electrophosphorescence efficiencies of 6.8 cd A-1 and 2.6%.