Efficient Organic Light‐Emitting Diodes Based on Ambipolar Doped Organic Single Crystals of Bis‐Styrylbenzene Derivatives

Abstract Ambipolar carrier transport in organic single crystals is essential to maximize exciton recombination and thus achieve high‐efficiency organic light‐emitting diodes (OLEDs). Herein, two bis‐styrylbenzene derivatives, 1,4‐bis(4‐methylstyryl)benzene (3PV‐Me) and 1,4‐bis(4‐trifluoromethylstyryl)benzene (3PV‐CF₃), are introduced into the construction of ambipolar 3PV‐CF₃ doped 3PV‐Me (3PV‐Me‐CF₃) single crystals. The same molecular skeleton of these two molecules endow them with similar molecular shapes and sublimation temperatures. Doping with 3PV‐CF₃ dopants is evaluated for their effect on the photophysical properties of host 3PV‐Me crystal. Systematic spectroscopic investigations and high‐resolution time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) depth profiling are further conducted to gain a deep insight into the doping details of 3PV‐Me‐CF₃ single crystals. Furthermore, their ambipolar carrier transport behavior is evaluated by the space‐charge‐limited current (SCLC) method, exhibiting nearly equal hole and electron mobilities. These ambipolar 3PV‐Me‐CF₃ single crystals are then utilized for the fabrication of single‐crystal OLEDs, which demonstrated an almost sixfold enhancement in the electroluminescence (EL) efficiency in comparison to the unipolar 3PV‐Me single‐crystal OLEDs. The findings reveal the great potential of well‐balanced ambipolar organic single‐crystalline semiconductors for the development of high‐performance single‐crystal optoelectronic devices.