Nanoscale Columnar Bundles Based on Multistranded Core–Shell Liquid Crystals of Perylene Bisimide J-Aggregate Donor–Acceptor Dyads for Photoconductivity Devices with Enhanced Performance Through Macroscopic Alignment

Abstract

Donor−acceptor dyads consisting of perylene bisimide (PBI) and trialkoxyphenyl−oligothiophene (TAPOT) units are reported that self-assemble into helical four-, six-, and seven-stranded hydrogen-bonded supramolecular polymers in solution and the columnar liquid-crystalline state. It is shown that the number of closely stacked and J-coupled PBI strands can be controlled by the incremental extension of the TAPOT wedge units in the bay position and the thereby tailored steric demand. Narcissistic self-sorting of TAPOT donor and PBI acceptor subunits facilitates the formation of core−shell structures creating individual percolation pathways for one-dimensional (1D) transport of photogenerated charge carriers. Macroscopic alignment of the nanoscale columnar structures by solution shearing enables anisotropic photoconductivity. Thus, selective orientation of the 1D charge-transporting domains parallel and perpendicular to the electrodes gives rise to an up to 90-fold increased photoresponse depending on the alignment quality. The intrinsic charge-separation and -transport properties were investigated by femtosecond transient absorption spectroscopy and flash-photolysis time-resolved microwave conductivity. These studies reveal a rising propensity for charge separation and transport upon increasing the conjugation length of the TAPOT donor and thereby increasing the size of the individual percolation pathways. Contrasting observations for intrinsic and macroscopic photoconductivities demonstrate the importance of processability in device performance.

Free Charge Carriers in Homo-Sorted π-Stacks of Donor–Acceptor Conjugates

“…153 SAXS/WAXS and their grazingincidence variants (GIWAXS/GISAXS) are indispensable tools in characterization of molecular arrangements in crystalline and liquid crystalline films as well. 154,155 Microscopic techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) furnish details on the morphology of the assemblies in film, which can be extended to the molecular level utilizing scanning tunneling microscopy (STM). 106 Nuclear magnetic resonance (NMR) spectroscopic methods such as diffusion ordered spectroscopy (DOSY), rotating frame and nuclear Overhauser enhancement spectroscopy (ROESY/ NOESY), and solid state techniques can report on the molecular packing and morphology of the assemblies.…”

“…Recently, Hecht et al reported a series of perylene bisimide (PBI) and trialkoxyphenyl-oligothiophene (TAPOT) 45 based D−A molecules that self-assemble into core−shell coaxial columnar structures in the liquid crystalline state (Figure 39a). 155 As the number of TAPOT units attached at the bay position of PBI increases, the number of PBI strands in the core of the supramolecular cable increases, leading to the formation of four-, six-, and seven-stranded helices by PBI 1T, PBI 2T, and PBI 3T, respectively (Figure 39b, c). Two-probe photoconductivity measurements conducted on supramolecular cables selectively oriented perpendicular and parallel to the electrodes using solution-shearing revealed a significant increase in photocurrent when the structures are aligned perpendicularly (Figure 39d).…”

“…X-ray scattering techniques such as small-angle X-ray diffraction (SAXS) and wide-angle X-ray diffraction (WAXS), particularly using synchrotron sources, have evolved as a reliable tool for the analysis of supramolecular structures in the solution phase and are frequently used in concert with molecular modeling to attain valuable information on the molecular arrangement within the crystalline assemblies . SAXS/WAXS and their grazing-incidence variants (GIWAXS/GISAXS) are indispensable tools in characterization of molecular arrangements in crystalline and liquid crystalline films as well. , Microscopic techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) furnish details on the morphology of the assemblies in film, which can be extended to the molecular level utilizing scanning tunneling microscopy (STM) . Nuclear magnetic resonance (NMR) spectroscopic methods such as diffusion ordered spectroscopy (DOSY), rotating frame and nuclear Overhauser enhancement spectroscopy (ROESY/NOESY), and solid state techniques can report on the molecular packing and morphology of the assemblies. − …”

Structure/Property Control in Photocatalytic Organic Semiconductor Nanocrystals

“…For example, the addition of electron‐rich trialkoxyphenyl‐oligothiophene (TAPOT) to electron‐deficient PDIs gave rise to a covalently linked donor–acceptor dyad (PDI‐T, Figure a). [ 48 ] Such dyad featured a well‐defined core‐shell crystalline architecture and thus created separated donor and acceptor domains in the crystal (Figure 6b), which could work as individual electron or hole transport pathways for charge separation and transport (Figure 6c). A further modification of the length TAPOT from one (PDI‐1T) to three (PDI‐3T) conferred good control of the domain size.…”

“…Reproduced with permission. [ 48 ] Copyright 2020, American Chemical Society. e) Synthetic procedures for C‐TCN (The circular area was carbon rings units and the rectangular one represented g‐C 3 N 4 ).…”