Highly Luminescent Solution-Grown Thiophene-Phenylene Co-Oligomer Single Crystals

Thiophene-phenylene co-oligomers (TPCOs) are among the most promising materials for organic light emitting devices. Here we report on record high among TPCO single crystals photoluminescence quantum yield reaching 60%. The solution-grown crystals are stronger luminescent than the vapor-grown ones, in contrast to a common believe that the vapor-processed organic electronic materials show the highest performance. We also demonstrate that the solution grown TPCO single crystals perform in organic field effect transistors as good as the vapor-grown ones. Altogether, the solution-grown TPCO crystals are demonstrated to hold great potential for organic electronics.</p

Pixelated full-colour small molecule semiconductor devices towards artificial retinas

Opto-stimulation of semiconductor-biointerfaces provides efficient pathways towards eliciting neural activity through selective spectral excitation. In visual prosthesis, tri-colour stimulation capability is the key to restoring full-colour vision. Here we report on investigation of organic photoactive π-conjugated donor–acceptor small molecules based on triphenylamine whose absorption spectra are similar to those of the photoreceptors of the human eye. Photoactive device fabrication and characterisation towards full colour, pixelated retinal prosthesis based on inkjet printing of these molecules is demonstrated, with round pixels reaching 25 microns in diameter. Photo-response is studied via interfacing with biological electrolyte solution and using long-pulse, narrow-band excitation. Both photo-voltage and photo-current responses in the devices with a ZnO hole-blocking interlayer show clear signatures of capacitive charging at the electrolyte/device interface, also demonstrating spectral selectivity comparable to that of human eye’ cones and rods

Ultrafast electron and hole dynamics in novel conjugated star-shaped molecules

Charge dynamics in organic photovoltaic blends based on novel star-shaped molecules are studied by ultrafast visible-IR spectroscopy. Pathways of intra- and intermolecular electron and hole transfer and their recombination are identified and discussed

Branched Electron-Donor Core Effect in D-π-A Star-Shaped Small Molecules on Their Properties and Performance in Single-Component and Bulk-Heterojunction Organic Solar Cells †

Star-shaped donor-acceptor molecules are full of promise for organic photovoltaics and electronics. However, the effect of the branching core on physicochemical properties, charge transport and photovoltaic performance of such donor-acceptor materials in single-component (SC) and bulk heterojunction (BHJ) organic solar cells has not been thoroughly addressed. This work shows the comprehensive investigation of six star-shaped donor-acceptor molecules with terminal hexyldicyanovinyl blocks linked through 2,2′-bithiophene π-conjugated bridge to different electron-donating cores such as the pristine and fused triphenylamine, tris(2-methoxyphenyl)amine, carbazole- and benzotriindole-based units. Variation of the branching core strongly impacts on such important properties as the solubility, highest occupied molecular orbital energy, optical absorption, phase behavior, molecular packing and also on the charge-carrier mobility. The performance of SC or BHJ organic solar cells are comprehensively studied and compared. The results obtained provide insight on how to predict and fine-tune photovoltaic performance as well as properties of donor-acceptor star-shaped molecules for organic solar cells

Solution-processed star-shaped oligomers in normal and inverted organic solar cells

The performance of three different star-shaped oligomers (SSOs) as electron donor materials for organic solar cells is investigated. These promising donor components are blended with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) fullerene acceptor and solution-processed normal and inverted organic solar cells are fabricated. These SSOs are based on a triphenylamine core and differ in the solubilizing groups and the oligothiophene arm length. We have found that the power conversion efficiency (PCE) is by 10-60% higher in the normal structure, mainly due to an enhanced open-circuit voltage and fill factor. The observed difference in device performance can be assigned partly to the lower leakage currents. By using contact angle measurements and atomic-force microscopy studies, we estimate the degree of vertical phase separation in bulk heterojunctions. The latter has a good correlation to the corresponding photocurrent differences obtained in the normal and inverted structure devices

Effect of oligothiophene π-bridge length in D-π-A star-shaped small molecules on properties and photovoltaic performance in single-component and bulk heterojunction organic solar cells and photodetectors

Donor-acceptor molecules with thiophene fragments as the π-bridge represent a promising class of materials for organic photovoltaics especially in single-component (SC) organic solar cells (OSCs) and other related applications. However, the effect of the oligothiophene π-bridge length on physicochemical properties, photophysics, charge transport, and photovoltaic performance of these materials has not been thoroughly addressed. Here, we report on the synthesis and comprehensive investigation of the series of star-shaped donor-acceptor molecules (0T–4T) with triphenylamine as a donor core linked through an oligothiophene π-bridge of variable length to the terminal hexyl-dicyanovinyl electron-withdrawing groups. We found that variation of the π-bridge length from 0 to 4 thiophene units strongly impacts their properties such as the solubility, highest occupied molecular orbital energy, optical absorption and photophysics, film morphology, phase behavior, and molecular packing as well as the charge carrier mobility. The performance of the SC and bulk heterojunction OSCs and photodetectors is comprehensively studied and compared. The results obtained provide insight into how to fine-tune and predict properties and photovoltaic performance of small molecules for organic solar cells and photodetectors