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

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.

本研究详述了含二苯并磷杂环戊二烯（dibenzophosphole）或磷杂环戊二烯（phosphole）结构单元的共轭体系的光物理、电化学及光电性能。由于二苯并磷杂环戊二烯衍生物在固态下光致发光（photoluminescence, PL）强度较弱，且相关器件稳定性不佳，因此该类材料并不适合用作有机发光二极管（OLED）的制备原料。通过调控磷杂环戊二烯的取代模式并对其磷原子进行化学修饰，可获得兼具热稳定性、光致发光与电致发光性能的衍生物。对硫代磷杂环戊二烯（thioxophospholes）溶液与薄膜的光学性能进行对比后发现，该类化合物在固态下不会形成聚集体；通过对三种新型衍生物的X射线衍射（X-ray diffraction）分析进一步验证了这一特性，该特性可有效提升化合物在固态下的荧光量子产率。与之相反，（磷杂环戊二烯）金(I)配合物在薄膜状态下会呈现宽谱发射，这一现象源于固态下聚集体的形成。研究人员已制备出以这类磷基衍生物作为发光层的单层及多层有机发光二极管器件，这类器件的发射光色与器件性能会随所用磷基材料的结构特性发生变化。值得注意的是，二(2-噻吩基)硫代磷杂环戊二烯可用作红光掺杂剂DCJTB的高效主体材料，而采用该类金配合物的器件则呈现宽谱发射特性。