Multiple resonance thermally activated delayed fluorescence (MR-TADF) emitters show great potentials for high color purity organic light-emitting diodes (OLEDs). However, the simultaneous realization of high photoluminescence quantum yield (PLQY) and high reverse intersystem crossing rate (k RISC ) is still a formidable challenge. Herein, a novel asymmetric MR-TADF emitter (2Cz-PTZ-BN) is designed that fully inherits the high PLQY and large k RISC values of the properly selected parent molecules. The resonating extended π-skeleton with peripheral protection can achieve a high PLQY of 96 % and a fast k RISC of above 1.0 × 10 5 s À 1 , and boost the performance of corresponding pure green devices with an outstanding external quantum efficiency (EQE) of up to 32.8 % without utilizing any sensitizing hosts. Remarkably, the device sufficiently maintains a high EQE exceeding 23 % at a high luminance of 1000 cd m À 2 , representing the highest value for reported green MR-TADF materials at the same luminescence.
Multi‐resonance thermally activated delayed fluorescence (MR‐TADF) material, which possesses the ability to achieve narrowband emission in organic light‐emitting diodes (OLEDs), is of significant importance for wide color gamut and high‐resolution display applications. To date, MR‐TADF material with narrow full width at half‐maximum (FWHM) below 0.14 eV still remains a great challenge. Herein, through peripheral protection of MR framework by phenyl derivatives, four efficient narrowband MR‐TADF emitters are successfully designed and synthesized. The introduction of peripheral phenyl‐based moieties via a single bond significantly suppresses the high‐frequency stretching vibrations and reduces the reorganization energies, accordingly deriving the resulting molecules with small FWMH values around 20 nm/0.11 eV and fast radiative decay rates exceeding 108 s−1. The corresponding green OLED based on TPh‐BN realizes excellent performance with the maximum external quantum efficiency (EQE) up to 28.9% without utilizing any sensitizing host and a relatively narrow FWHM of 0.14 eV (28 nm), which is smaller than the reported green MR‐TADF molecules in current literatures. Especially, the devices show significantly reduced efficiency roll‐off and relatively long operational lifetimes among the sensitizer‐free MR‐TADF devices. These results clearly indicate the promise of this design strategy for highly efficient OLEDs with ultra‐high color purity.
In the last decades, organic light-emitting diodes (OLEDs) have been rapidly developed and occupy an important position in the lighting and display market. Early conventional fluorescent OLEDs materials can only...
Achieving high external quantum efficiency (EQE) for non-doped deep blue fluorescent organic light-emitting diodes (OLEDs) with Commission international de I'Eclairage (CIE) coordinate of CIEy < 0.08 remains a big challenge....
Axicon is an interesting optical element for its optical properties. This paper presents an approach to dynamically generated tunable axicons with a spatial light modulator (SLM). 256-level phase computer-generated holograms (CGHs) were loaded into the SLM to simulate the positive and negative axicons. The intensity distributions of beams passing through these axicons were analyzed with the principle of blazed grating and Fresnel diffraction; and the diffraction patterns were obtained theoretically in terms of zero-order Bessel beams and annular hollow beams, corresponding to the positive and negative axicons, respectively. Experimental results verified that the diffraction patterns have the same distribution as the real axicon. The types of the axicon and the axicon’s parameters can be easily altered through changing the CGHs.
The pursuit for efficient deep blue material is an ever‐increasing issue in organic optoelectronics field. It is a long‐standing challenge to achieve high external quantum efficiency (EQE) exceed 10% at brightness of 1000 cd m−2 with a Commission International de L'Eclairage (CIEy) <0.08 in non‐doped organic light‐emitting diodes (OLEDs). Herein, this study reports a deep blue luminogen, PPITPh, by bonding phenanthro[9,10‐d]imidazole moiety with m‐terphenyl group via benzene bridge. The non‐doped OLED based on PPITPh exhibits an exceptionally high EQE of 11.83% with a CIE coordinate of (0.15, 0.07). The EQE still maintains 10.17% at the brightness of 1000 cd m−2, and even at a brightness as high as 10000 cd m−2, an EQE of 7.5% is still remained, representing the record‐high result among non‐doped deep‐blue OLEDs at 1000 cd m−2. The unprecedented device performance is attributed to the reversed intersystem crossing process through hot exciton mechanism. Besides, the maximum EQE of orange phosphorescent OLED with PPITPh as host is 32.02%, and remains 31.17% at the brightness of 1000 cd m−2. Such minimal efficiency roll‐off demonstrates that PPITPh is also an excellent phosphorescent host material. The result offers a new design strategy for the enrichment of high‐efficiency deep blue luminogen.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.