Highly Ordered Supramolecular Materials of Phase‐Separated Block Molecules for Long‐Range Exciton Transport

Abstract

Efficient energy transport over long distances is essential for optoelectronic and light-harvesting devices. Although self-assembled nanofibers of organic molecules are shown to exhibit long exciton diffusion lengths, alignment of these nanofibers into films with large, organized domains with similar properties remains a challenge. Here, it is shown how the functionalization of C 3 -symmetric carbonyl-bridged triarylamine trisamide (CBT) with oligodimethylsiloxane (oDMS) side chains of discrete length leads to fully covered surfaces with aligned domains up to 125 × 70 μm 2 in which long-range exciton transport takes place. The nanoscale morphology within the domains consists of highly ordered nanofibers with discrete intercolumnar spacings within a soft amorphous oDMS matrix. The oDMS prevents bundling of the CBT fibers, reducing the number of defects within the CBT columns. As a result, the columns have a high degree of coherence, leading to exciton diffusion lengths of a few hundred nanometers with exciton diffusivities (≈0.05 cm 2 s −1 ) that are comparable to those of a crystalline tetracene. These findings represent the next step toward fully covered surfaces of highly aligned nanofibers through functionalization with oDMS.

Viscoelastic Fluorescent π-Conjugated Polymer Liquids toward Direct Visualization of Microphase Separation

“…As shown in Figure S7b,c, the PPTBT / PPT blending sample exhibited two independent and separated glass-transition temperatures at −27 and −5 °C, which correspond to the glass-transition temperature from pristine PPTBT (−27 °C) and PPT (−5 °C), respectively. This result suggested that the phase-separated phenomena between PPTBT and PPT , although they were functionalized, resemble side chains along the polymer backbone. , The PPTBT / PPT blend showed a high-contrast and well-resolved phase separation structure with dual colors. By comparison with the original emission color of PPT , the green emissive, irregular-shaped, and large-sized domains should be the PPT -rich phase, which is embedded in the red emissive continuous PPTBT phase.…”

“…This result suggested that the phase-separated phenomena between PPTBT and PPT, although they were functionalized, resemble side chains along the polymer backbone. 43,44 The PPTBT/PPT blend showed a high-contrast and well-resolved phase separation structure with dual colors. By comparison with the original emission color of PPT, the green emissive, irregular-shaped, and large-sized domains should be the PPTrich phase, which is embedded in the red emissive continuous PPTBT phase.…”

Trade-off between processability and device performance in donor–acceptor semiconductors revealed using discrete siloxane side chains

“…Linear and branched derivatives Si 7 H , Si 11 H , Si 15 H and Si 7B H and Si 15B H were synthesized following literature protocol. 25,26 From either commercially available Si 3 H or previously synthesized Si 7 H , the respective hydroxysiloxanes were formed using Pd/C in a dioxane/water system. These were subsequently mixed with dichloromethylsilane in pyridine/toluene to yield the desired branched side chains on a multigram scale in moderate to good yield (65–82%).…”

“…In previous years, we have reported on the synthesis of elongated and branched o DMS as side chains for supramolecular polymers. 25,26 We envision that the use of these side chains in semicrystalline D–A polymers will increase their processability. Furthermore, we aim to elucidate the effect of such pendants on the electronic properties of the semiconductor in an OFET device.…”

1,5-Diiodocycloctane: a cyclane solvent additive that can extend the exciton diffusion length in thick film organic solar cells

“…35–39 However, extreme mismatch remains in the L D and the large phase separation scale of the thick-film, 40–42 which will hinder a significant fraction of excitons from crossing a longer distance and diffusing into the D/A interfaces, leading to the reduced photocurrent conversion efficiency. 43,44 In addition, a small L D can further lead to increased trap state density, low and unbalanced charge transport, and space charge accumulation in the active layer, all of which can result in severe charge recombination in thick-film devices. 45–48 A few efforts have been made to solve these issues through materials development and interfacial engineering, such as the synthesis of temperature-dependent aggregative polymers, the employment of a layer-by-layer approach and the introduction of a fullerene liquid crystal into the active layer.…”