Synthesis and optoelectronic properties of a novel dinuclear cyclometalated platinum(II) complex containing triphenylamine-substituted indolo[3,2-b]carbazole derivative in the single-emissive-layer WPLEDs

A novel bi-picolinic acid derivative of H2dipic-BTICz containing binary triphenylamine-substituted indolo[3,2-b]carbazole (BTICz) unit and its dinuclear platinum(II) complex of (dfppy)2Pt2(dipic-BTICz) were synthesized as a single-component emitter used in the white polymer light-emitting diodes (WPLEDs), where dfppy is 2-(2,4-difluorophenyl)pyridine and dipic-BTICz is an anion of H2dipic-BTICz. The photophysical and electrochemical properties of (dfppy)2Pt2(dipic-BTICz) were investigated. Compared with the reported mononuclear platinum complex of (dfppy)Pt(pic), (dfppy)2Pt2(dipic-BTICz) exhibited a red-shifted photoluminescent peak at 434 nm in dilute dichloromethane (10−5 M), but a weakened and red-shifted aggregation emission peak at 640 nm besides its intrinsic emission at 445 nm in its neat films. Stable pure white emissions with CIE coordinates of (0.325±0.005, 0.345±0.015) and a maximum brightness of 208 cd/m2 were observed in the (dfppy)2Pt2(dipic-BTICz)-doped single-emissive-layer (SEL) PLEDs using a blend of poly(vinylcarbazole) and 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as a host matrix at 1 wt % dopant concentrations under applied voltages from 9 to 14 V. It indicates that the intrinsic and aggregation emissions of this dinuclear platinum complex were effectively tuned by inserting a new BTICz fluorophore in the dual picolinic acid derivative. Therefore, it is a promising single-component emitter to get white emission in SEL PLEDs.

A novel heterodinuclear cyclometalated Pt(II) complex of (dfppy)2Pt2(dipic-BTICz), containing blue-emitting fluorophore (BTICz) via non-conjugatedly inserted into the dual picolinic acid derivative, was synthesized successfully. Using this novel dinuclear platinum complex as a single-component emitter, stable white emission with a maximum brightness of 208 cd/m2 was achieved in the single-emissive-layer PLEDs at the doping concentration of 1 wt % and different applied voltages from 9 to 14 V.