Tweaking the Optoelectronic Properties of S-Doped Polycyclic Aromatic Hydrocarbons by Chemical Oxidation.

Peri-thiaxanthenothiaxanthene, an S-doped analog of peri-xanthenoxanthene, is used as a polycyclic aromatic hydrocarbon (PAH) scaffold to tune the molecular semiconductor properties by editing the oxidation state of the S-atoms. Chemical oxidation of peri-thiaxanthenothiaxanthene with H O led to the relevant sulfoxide and sulfone congeners, whereas electrooxidation gave access to sulfonium-type derivatives forming crystalline mixed valence (MV) complexes. These complexes depicted peculiar molecular and solid-state arrangements with face-to-face π-π stacking organization.

Supramolecular Chalcogen-Bonded Semiconducting Nanoribbons at Work in Lighting Devices.

This work describes the design and synthesis of a π-conjugated telluro[3,2-β][1]-tellurophene-based synthon that, embodying pyridyl and haloaryl chalcogen-bonding acceptors, self-assembles into nanoribbons through chalcogen bonds. The ribbons π-stack in a multi-layered architecture both in single crystals and thin films. Theoretical studies of the electronic states of chalcogen-bonded material showed the presence of a local charge density between Te and N atoms.

Multivariate Analysis Identifying [Cu(N^N)(P^P)] Design and Device Architecture Enables First-Class Blue and White Light-Emitting Electrochemical Cells.

White light-emitting electrochemical cells (LECs) comprising only [Cu(N^N)(P^P)] have not been reported yet, as all the attempts toward blue-emitting complexes failed. Multivariate analysis, based on prior-art [Cu(N^N)(P^P)] -based thin-film lighting (>90 papers) and refined with computational calculations, identifies the best blue-emitting [Cu(N^N)(P^P)] design for LECs, that is, N^N: 2-(4-(tert-butyl)phenyl)-6-(3,5-dimethyl-1H-pyrazol-1-yl)pyridine and P^P: 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene, to achieve predicted thin-film emission at 490 nm and device performance of 3.8 cd A @170 cd m .

Towards rainbow photo/electro-luminescence in copper(i) complexes with the versatile bridged bis-pyridyl ancillary ligand.

The synthesis and characterization of a family of copper(i) complexes bearing a bridged bis-pyridyl ancillary ligand is reported, highlighting how the bridge nature impacts the photo- and electro-luminescent behaviours within the family. In particular, the phosphonium bridge led to copper(i) complexes featuring good electrochemical stability and high ionic conductivity, as well as a stark blue-to-orange luminescence shift compared to the others. This resulted in high performance light-emitting electrochemical cells reaching stabilities of 10 mJ at ca.

Revealing the Impact of Heat Generation Using Nanographene-Based Light-Emitting Electrochemical Cells.

Self-heating in light-emitting electrochemical cells (LECs) has been long overlooked, while it has a significant impact on (i) device chromaticity by changing the electroluminescent band shape, (ii) device efficiency because of thermal quenching and exciton dissociation reducing the external quantum efficiency (EQE), and (iii) device stability because of thermal degradation of excitons and eliminate doped species, phase separation, and collapse of the intrinsic emitting zone. Herein, we reveal, for the first time, a direct relationship between self-heating and the early changes in the device chromaticity as well as the magnitude of the error comparing theoretical/experimental EQEs-that is, an overestimation error of . 35% at usual pixel working temperatures of around 50 °C.

Bright, stable, and efficient red light-emitting electrochemical cells using contorted nanographenes.

This work rationalizes, for the first time, the electroluminescent behavior of a representative red-emitting contorted nanographene -i.e., hexabenzoovalene derivative - in small molecule light-emitting electrochemical cells (SM-LECs).

Polypyridyl ligands as a versatile platform for solid-state light-emitting devices.

The replacement of inorganic semiconductors with molecule-based compounds for applications in current-to-light conversion has led to a significant increase in interdisciplinary collaborations worldwide, affording new improved organic-light emitting diodes (OLEDs) ripe for commercial applications, as well as light-emitting electrochemical cells (LECs) that have recently started to head to the market. This review highlights the role that transition metal coordination complexes (TMCs) have played in advancing the field of molecular electronics, from early conception to the advanced development of several polypyridyl complexes currently pursued for both OLED and LEC concepts. In this context, the design and synthesis of Ir(iii), Pt(ii), Cu(i) and Ag(i) complexes as the emissive components of OLEDs and LECs are thoughtfully presented.

Photoluminescent Cu(i) vs. Ag(i) complexes: slowing down emission in Cu(i) complexes by pentacoordinate low-lying excited states.

This work describes the synthesis, and structural, spectroscopic, and theoretical studies of a mononuclear silver(i) complex with the formula [Ag(Xantphos)(4,4'-(MeO)2-2,2'-bipy)]BF4·DCM (1·BF4) [Xantphos: 4,5-bis(diphenylphosphino)-9,9'-dimethylxanthene]. We provide meaningful insights into the enhancement of the photoluminescence features of this silver(i) complex compared to its copper(i) analogue.

Novel Ligand and Device Designs for Stable Light-Emitting Electrochemical Cells Based on Heteroleptic Copper(I) Complexes.

This work reports on the positive impact of (i) attaching methoxy groups at the ortho position of the bipyridine ligand (6,6'-dimethoxy-2,2'-bipyridine) in heteroleptic copper(I) complexes belonging to the [Cu(bpy)(POP)] family, and (ii) a new device design comprising a multilayered architecture to decouple hole/electron injection and transport processes on the performance of light-emitting electrochemical cells (LECs). In short, the substituted complex showed enhanced thermal- and photostability, photoluminescence, and ionic conductivity features in thin films compared to those of the archetypal complex without substitution. These beneficial features led to LECs outperforming reference devices in terms of luminance, stability, and efficacy.

Peripheral Substitution of Tetraphenyl Porphyrins: Fine-Tuning Self-Assembly for Enhanced Electroluminescence.

This study reports the synthesis of two novel zinc porphyrin families bearing four or eight alkoxy chains at their peripheral phenyl rings, with the length of the alkoxy chains ranging from 2, to 6, and to 12 carbon atoms. All zinc porphyrin derivatives were fully characterized with respect to their photophysical and electrochemical features. The zinc porphyrins could be processed into thin films which, depending on the length of the alkoxy chains on the aryl substituents, were found to be either of an ordered or a disordered nature, as it is revealed by spectroscopic and microscopic techniques.