No abstract

Thermally activated delayed fluorescence (TADF) materials that are able to realize electroluminescence showing simultaneously narrow emission band, high color purity, and high efficiency are highly demanded for display applications. Up to now, a few blue emissive TADF materials with such characteristics have been reported, while green TADF materials with such features are extremely scarce. Herein, two TADF compounds with highly efficient narrowband bluish green/green emission (full‐width at half‐maximum (FWHM): 22 and 21 nm in toluene) induced by multiple resonance effect are reported. An optimized organic light‐emitting diode based on the green emissive compound shows a fairly narrow electroluminescent spectrum (FWHM: 33 nm), as well as an excellent color purity with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.20, 0.65), which is a close resemblance to the standard green‐light CIE coordinates of (0.21, 0.71) defined by the National Television System Committee. Meanwhile, the maximum external quantum efficiency (EQE) up to 25.5% is achieved and a high EQE of 20.1% is maintained at a practical high luminance of 1000 cd m−2. The outstanding device performance of the compound makes it attractive for potential practical applications.

The development and enrichment of organic materials with narrowband emission in longer wavelength region beyond 515 nm still remains a great challenge. Herein, a significant synthetic methodology for narrowband emission materials has been proposed to functionalize multiple resonance (MR) skeleton and generate a universal building block, namely, the key intermediate DtCzB-Bpin, which can be utilized to construct multifarious thermally activated delayed fluorescence (TADF) materials with high color purity through a simple one-step Suzuki coupling reaction. Based on the unique synthetic strategy, a series of efficient narrowband green TADF emitters has been constructed by localized attachment of 1,3,5-triazine and pyrimidine derivativesbased acceptors onto B-N-containing MR framework with 1,3-bis(3,6-di-tert-butylcarbazol-9-yl)benzene (DtCz) as ligand. The precise modulation of acceptor is an ingenious approach for achieving bathochromic shift and narrowband emission simultaneously. The DtCzB-TPTRZ-based organic light-emitting diode (OLED) exhibits pure green emission with Commission Internationale de L'Eclairage (CIE) coordinates of (0.23, 0.68), and maximum external quantum efficiency (EQE) of 30.6% as well as relatively low efficiency roll-off.

Comparative study of the photocatalytic performance for the degradation of different by ZnIn2S4 based on the adsorption of dyes, the active species and the degradation pathway.

A pure organic molecule 2,6-di­(phenothiazinyl)­naphthalene (DPTZN) with room-temperature phosphorescence (RTP) features was developed. Remarkably, a triazine-benzimidazole-based molecule TRZ-BIM can significantly improve the RTP efficiency of DPTZN in DPTZN:TRZ-BIM blend films. The photoluminescence quantum yield (PLQY) of 10 wt % DPTZN:TRZ-BIM blend film is 38%. The RTP property of DPTZN:TRZ-BIM blend films was characterized by steady, time-resolved, and temperature-dependent emission spectra. An organic light-emitting diode (OLED) with 10 wt % DPTZN:TRZ-BIM blend film as the emitting layer showed a high maximum external quantum efficiency of 11.5%, current efficiency of 33.8 cd A–1, and power efficiency of 32.6 lm W–1. Herein, we have developed an efficient approach to achieve precious-metal-free organic films that can be employed to fabricate high-performance phosphorescence OLEDs.