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Organic light-emitting diodes must be engineered to circumvent efficiency limits imposed by the ratio of triplet to singlet exciton formation, following electron-hole capture. Here, authors unlock energy transfer channels between singlet, triplet and doublet excitons using thermally activated delayed fluorescence and radical emitters towards more efficient light-emitting devices.

We report organic molecules showing both efficient luminescence and near-unity generation yield of excited states with high spin multiplicity, simultaneously supporting a high efficiency of initialization, spin manipulations and light-based readout at room temperature.

Exploiting the energy transfer between the host triplet states and spin doublet exciton states of a radical organic emitter enables near-infrared organic light-emitting diodes with an external quantum efficiency up to 9.6% at an emission wavelength of 800 nm.

Despite advances in the design of thermally activated delayed fluorescence (TADF) emitters for devices, the effect of spin interactions is not well understood. Here, the authors report the role of spin-vibronic coupling in TADF organic emitters using transient electron spin resonance spectroscopy.

Proposed as the source of the light-dependent magnetic compass in migratory birds, the radical pair mechanism is thought to operate in flavoproteins in the retina. Now, it has been demonstrated that the primary magnetic field effect on flavin photoreactions can be chemically amplified by slow radical termination reactions under conditions of continuous photoexcitation.

Organic light-emitting devices containing radical emitters can achieve an efficiency of 27 per cent at deep-red and infrared wavelengths based on the excitation of spin doublets, rather than singlet or triplet states.

Among double [n]helicenes, known for their simplicity and configurational stability when n exceeds 4, double [5]helicene imides remain underexplored. Here, the authors develop a stepwise synthetic route to access these diimides, as well as planar nanographene diimides via C-shaped mono-[5]helicene diimide, using benzannulation and Scholl reactions for progressive π-extension, reporting fluorescence quantum yields of up to 63% in solution and 32% in the solid state.

A low singlet-triplet energy gap, necessary for delayed fluorescence organic semiconductors, results in a small radiative rate that limits performance in OLEDs. Here, the authors show that it is possible to reconcile these conflicting requirements in materials that can access both high oscillator strength intramolecular excitations and intermolecular charge transfer states.

A molecular design strategy for reducing the vibration-induced non-radiative losses in emissive organic semiconductors is realized by decoupling excitons from high-frequency vibrations.

An investigation on the electronic transitions of organic radicals allows us to identify design rules to increase the oscillator strength of these emitters and obtain efficient radical-based light-emitting diodes operating in the visible range.

Covalent organic frameworks (COFs) find increasing application as sensor material, but fast switching solvatochromism was not realized. Here the authors demonstrate that combination of electron-rich and -deficient building blocks leads to COFs which fast and reversibly change of their electronic structure depending on the surrounding atmosphere.

The role of the dielectric environment in thermally activated delayed fluorescence (TADF) is not yet fully understood. Here the authors reveal the relevance of environment–emitter interactions in gating the reverse intersystem crossing and its particular relevance in dipolar TADF emitters.

An organic molecule, 5Cz-TRZ, with multiple donor units supports fast reverse intersystem crossing, allowing fabrication of high-performance organic light-emitting diodes.

Organic radical molecules violating the Aufbau principle are shown to reach high luminescence quantum yield and photostability, with potential applications for deep-red and near-infrared light-emitting sources.