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Carrier mobility is one of the key issues for applications of organic semiconductors in electronic and optoelectronic devices. Organic single crystals possess much higher carrier mobility compared to amorphous films. However, unipolar properties with unbalanced hole and electron transporting ability have been a bottleneck for the high performance of organic single crystal‐based devices. Here, well‐balanced ambipolar organic single crystals are developed by mixing of n‐ and p‐type molecules with maintained single‐crystalline structures. Carrier mobility of the ambipolar single crystals is manipulated by tuning the mixing ratio, and nearly equal hole and electron mobility can be achieved. Highly efficient single crystal‐based organic light‐emitting devices (OLEDs) are demonstrated by employing the ambipolar crystals as the mixed host for a red emitter pentacene to realize efficient exciton confinement and energy transfer within the emissive layer. As a result, maximum luminance of 5467 cd m−2 and current efficiency of 2.82 cd A−1 are achieved, which represents, to the best of the authors' knowledge, the record performance for the organic single crystal‐based OLEDs to date. The strategy to manipulate the charge‐transport properties of the organic single crystals in this work represents a significant step toward practical applications of the organic single crystals in optoelectronics. [ABSTRACT FROM AUTHOR]

Organic single crystals have attracted immense attention in the field of organic light-emitting devices (OLEDs), owing to their unique advantages of long-range molecular ordering, high carrier mobility, high fluorescent quantum yield and low impurity content. Development of high-performance organic single crystal-based OLEDs with narrow-band emission is critical for high-purity displaying, yet it is still a major challenge to obtain a crystal-based OLED with both narrow fullwidth at half maximum (FWHM) and high electroluminescence (EL) performance. Here, molecular doping engineering is employed by taking 2,6-diphenylanthracene (DPA) as host crystal and pentacene (Pen) as red guest emitter material. 2,2′-Bis[4-(trifluoromethyl)phenyl]-5,5′-bithiazole (BTPB) with strong electron-withdrawing ability are further doped for the growth of ambipolar crystals in order for balanced hole and electron mobility. As a result, DPA: 3% Pen: 15% BTPB crystal-based OLEDs exhibit a maximum luminance and current efficiency of 10,850 cd m−2 and 1.91 cd A−1, respectively, and an EQE of 1.51%. The obtained red-light-emission with a narrow FWHM increases high color purity of crystal-based OLEDs. It demonstrates that high-performance crystal-based OLEDs with narrow-band emission are of great significance for the development of organic electronics, especially for display and lighting applications. Molecular doping engineering is employed by taking DPA single crystals as host matrix and pentacene as red guest emitter. BTPB with strong electron-withdrawing ability is further doped for obtaining ambipolar crystals. DPA: 3% Pen: 15% BTPB crystal-based OLEDs exhibit a red-light-emission with a narrow FWHM and high-efficiency, which are of great significance for the development of organic single crystal-based electronics. [Display omitted] • Doping of pentacene into host DPA crystal enable narrow-band red-light-emission. • Ambipolar crystals obtained by doping n -type BTPB for balanced charge mobility. • Narrow-band EL emission from crystal-based OLEDs increases a high purity. • DPA: 3% Pe: 15% BTPB crystal-based OLEDs exhibit the highest EL performance. [ABSTRACT FROM AUTHOR]