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Nickel(II) dihalide precatalysts with bidentate nitrogen ligands are widely used in cross-coupling reactions, notably in combination with photosensitizers, forming catalytic systems that currently drive major conceptual and synthetic thrusts within organic chemistry. Here the authors show a general mechanism by which these precatalysts are converted to the reduced, catalytically active species, using a range of characterization and spectroscopic techniques.

A dual interfacial hydrogen-bond passivation strategy and a hybrid copper–iodide are used to fabricate deep-blue light-emitting diodes with excellent external quantum efficiency and lifetime.

Singlet fission produces two low-energy triplet excitons that are difficult to dissociate into free charges. Now, separate optima in charge yield have been observed as a function of driving force for singlet and triplet excitons in pentacene. At optimal driving forces, the triplet-exciton dissociation rate is at least five orders of magnitude smaller than the singlet-exciton dissociation rate.

Ammonium bromide is shown to passivate deep traps on FAPbBr₃ surfaces, improving the charge collection efficiency to near unity in perovskite gamma-ray devices. The approach yielded tenfold improvements in dark current, and the energy resolution of ¹³⁷Cs spectra acquired using FAPbBr₃ detectors was improved from 5.7% to 1.7%.

Photoinduced carrier-generation in individual semiconducting single-walled carbon nanotubes is controversial. Here, the authors demonstrate that free carriers can be generated even in the absence of dissociating interfaces by performing time-resolved microwave conductivity on solutions of dispersed nanotubes.

Perovskite-based solar cells are often fabricated by methods that are not industrially scalable. Here, Yang et al. develop an ink formulation which gives similar devices by spin coating, the lab-scale standard, and blade coating, which is a more scalable, industry-relevant deposition method.

Single crystals of lead halide perovskites exhibit good optoelectronic properties. Here, the authors study and deduce the mechanism for crystallisation and show how controlling dissolution of colloids through varying the acidity and temperature can improve the quality of the single crystals.

The influence of the thermodynamic driving force for photoinduced electron-transfer between single-walled carbon nanotubes and fullerene derivatives has been investigated. The Marcus inverted region and small reorganization energies were observed for this model organic heterojunction. Small reorganization energies aid in minimizing energy losses for solar conversion to electricity or fuels.

Ion pairing is ubiquitous in low-dielectric-constant solvents, but whether it influences the reactivity of common cationic photoredox catalysts has been unclear. However, it has now been shown that ion pairing is responsible for a 4-fold modulation in reactivity in a prototypical Ir(III) complex and is explained by excited-state ion-pair reorganization.

Difficulties in controlling the nucleation and growth of thin films of organic semiconductors have impaired progress in organic electronics. Now, efficient control of the crystallite nucleation and microstructure of a broad range of organic semiconductors without detriment to their electronic properties has been achieved through the addition of small quantities of additives—a widely used strategy in bulk polymer crystallization.