Toward Functional π-Conjugated Organophosphorus Materials:  Design of Phosphole-Based Oligomers for Electroluminescent Devices

Abstract

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.

Calix[4]arene-fused phospholes

“…4 and Table 2). The observed bands are characteristic of P-bridged biphenyl derivatives, [21] and, as expected, an analogous band could not be detected for the phosphine complex 4 (Fig. S3).…”

Enhanced phosphorescence in dibenzophosphole chalcogenide mixed crystal

“…13 There are several reports on application of p-conjugated phosphorus compounds as OLED emitter 13 and electron transporting materials. 14 Recently, we have investigated the photophysical properties of 9-phenyl-9-dibenzophosphole chalcogenides (oxide, sulfide, and selenide) (Fig.…”

Dendrimeric Oligo(phenylenevinylene)‐Extended Dithieno[3,2‐b:2′,3′‐d]phospholes—Synthesis, Self‐Organization, and Optical Properties

“…[13] RØau and co-workers were among the first to incorporate the phosphole moiety in extended p-conjugated materials [14] and to utilize these in phosphole-based OLED devices. [15] A few years ago, we introduced the dithieno[3,2-b:2',3'-d]phos-A C H T U N G T R E N N U N G phole system (1, Scheme 1) to this field of research. [16] Our building block, which conjoins two thiophene subunits with a central phosphole moiety through annelation, allows for the selective and efficient tuning of the (opto)electronic properties of the materials by functionalization of phosphorus atom or the main scaffold.…”