A lack of an efficient and stable blue device is a critical factor restricting the development of organic light-emitting diode (OLED) technology that is currently expected to be overcome by employing thermally activated delayed fluorescence (TADF). Here, we investigate the TADF and electroluminescence (EL) performance of six carbazole/triphenyltriazine derivatives in different hosts. A good linearity between lg(LT50/k F 2 ) and the EL emission wavelength is found, where LT50 is the half-life of the devices and k F is the fluorescence rate of the emitters, suggesting the dominance of the singlet exciton energy and lifetime in device stability. An indolylcarbazole/triphenyltriazine derivative (ICz-TRZ) with the capability to suppress solid-state solvation exhibits blue-shifted emission and an increased k F (1.5 × 10 8 s −1 ) in comparison to the control emitters in doped films. ICz-TRZ-based devices achieve a maximum external quantum efficiency (EQE) of 18% and an EQE of 5.5% at a very high luminance of 7 × 10 4 cd/m 2 . Ignoring the poor electrochemical stability of ICz-TRZ, the device offers an LT50 approaching 100 h under an initial luminance of 1000 cd/m 2 and CIE coordinates of (0.14, 0.19). The findings in this work suggest that computer-aided design of high k F TADF emitters can be an approach to realize efficient and stable blue OLEDs.

The degradation in TADF OLEDs is found to be governed by the radical electrophilic substitutions between two charge-transfer (CT) excitons. Expanding the mean localization distance (RLOL) of hole in the CT state can improve device stability.

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A single‐layer reflective metasurface with linear‐to‐linear polarization and circularly polarized reflection under linearly polarized incident wave is investigated in this work. The unit cell of our designed metasurface is formed by the inner cross structures and the outer two pairs of serpentine lines etched on the substrate, and metallic copper is attached to the back of the substrate. The simulation results are as follows that the linearly polarized reflected wave in the middle frequency ranges of 9.33–11.77 GHz (the fractional bandwidth of 23.1% and the polarization conversion ratio over 95%) is realized when the co‐polarization reflection coefficients are within −14 dB under the y‐polarized illuminated wave. Besides, the linear‐to‐circular polarization state is completed when the y‐polarized wave impinges on this metasurface in two nonadjacent frequency bands from 5.95 to 8.80 GHz and 12.68 to 15.58 GHz, which are corresponding to the relative bandwidth of 38.6% and 20.5% respectively according to the 3 dB axial ratio bandwidth property. In addition, the physical mechanism is explained and the sample of this metasurface converter is manufactured and tested. The experiment results are corresponding to the simulation results, which prove the reliability of the simulation results.

A dual-passband single-polarized converter based on the band-stop frequency selective surface (FSS) with a low radar cross-section (RCS) is designed in this article. The unit cell of the proposed converter is formed by a polarization layer attached to the band-stop frequency selective surface. The simulation results reveal that the co-polarization reflection coefficients below −10 dB are achieved in 3.82–13.64 GHz with a 112.4% fractional bandwidth (the ratio of the signal bandwidth to the central frequency). Meanwhile, a polarization conversion band is realized from 8.14 GHz to 9.27 GHz with a polarization conversion ratio which is over 80%. Moreover, the 1 dB transmission window is obtained in two non-adjacent bands of 3.42–7.02 GHz and 10.04–13.91 GHz corresponding to the relative bandwidths of 68.9% and 32.3%, respectively. Furthermore, the radar cross-section of the designed structure can be reduced in the wideband from 2.28 GHz to 14 GHz, and the 10 dB RCS reduction in the range of 4.10–13.35 GHz is achieved. In addition, the equivalent circuit model of this converter is established, and the simulation results of the Advanced Design System (ADS) match well with those of CST Microwave Studio (CST). The archetype of the designed converter is manufactured and measured. The experiment results match the simulation results well, which proves the reliability of the simulation results.