A wide‐gap host matrix is a major obstacle detrimentally influencing the performance of hyperfluorescent organic light‐emitting diodes since it substantially increases driving voltage. Moreover, these hyperfluorescent devices typically require at least three components in their emitting layer, which is unfavorable for mass production. To tackle the issue, hyperfluorescent organic light‐emitting diodes are reported based on a two‐component emissive system of carbene–metal–amide donors and conventional fluorescent acceptors. A significant reduction of the driving voltage versus three‐component hyperfluorescent devices at practical brightness (1000 cd m–2) is demonstrated, leading to a doubling of power conversion efficiency for some composites. From an analysis of thin‐film photophysics, it is shown that operational efficiency is limited by Dexter energy transfer between donors and acceptors, which may be reduced by tert‐butyl steric substituents, providing new targets for molecular design. While reducing driving voltage, matrix‐free hyperfluorescent devices also achieve a maximum external quantum efficiency of 16.5%.

Organic radicals with fluorescence from doublet‐spin energy manifolds circumvent efficiency limits from singlet–triplet photophysics in organic light‐emitting diodes (OLEDs). The singly occupied molecular orbital (SOMO) in radicals enables the higher potential performance. The SOMO also presents substantially lower energy frontier orbitals compared to conventional fluorescent emitters for device operation, which can cause severe electron trapping that limits the performance of radical OLEDs. To improve optoelectronic performance, electron donor–acceptor‐mixed hosts are used to control charge transport for enhanced radical electroluminescence by charge recombination on SOMO and frontier orbitals. The (2‐chloro‐3‐pyridyl)bis(2,4,6‐trichlorophenyl)methyl‐based radical is designed to test the charge‐controlled device architectures in OLEDs by transient analysis and device characterization studies. Efficient radical OLEDs with 4.7% maximum external quantum efficiency are reported—showing substantial advances in performance for OLEDs with peak emission beyond 800 nm. In addition, substantially improved performance at higher current density operation and more than two orders of higher lifetime stability are achieved with mixed hosts. These results enable pathways to infrared‐emitting devices with applications ranging from communications to bioimaging.

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Oscillations may cause both economic and technical problems such as a reduction in overall system reliability. Therefore, detecting and preventing oscillatory behavior that affects power systems is important. This paper proposes an oscillation recognition method that includes monitoring and extracting features in a recursive and sequential manner in a time-series measurement in power systems. We propose a geometric feature extraction process for recognizing oscillations by constructing an average system and Poincaré map for time-series measurement. The proposed process provides the features of a system's damping and frequency of oscillation, and the developed monitoring systems are based on nonlinear dynamics. The circulating oscillatory behavior is represented on a finite-integer-delay embedded time-series plane, extracted by a Poincaré map construction, and examined directly along the trajectory to monitor the features of the oscillation according to damping and frequency. Oscillatory behavior recognition is tested on IEEE's second benchmark system for subsynchronous resonance to verify the fast extraction of oscillation components. In addition, a case study for Korean power systems with a high penetration of renewable energy and application on actual measurement data is carried out to demonstrate the practical application of the process.