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A supramolecular hydrogel providing a biomimetic neural microenvironment with improved mechanical properties presents a laminin-derived neuro-inductive peptide epitope that induces multipotent stem cells into neural-lineage cells.

Observation of thermally activated delayed fluorescence (TADF) in conjugated systems redefined the molecular design approach to realize highly efficient organic light emitting diodes (OLEDs) in the early 2010s. Enabling effective reverse intersystem crossing (RISC) by minimizing the difference between singlet and triplet excited state energies (ΔE ST ) is proven to be a widely applicable and fruitful approach, which results in remarkable external quantum efficiencies (EQE). The efficacy of RISC in these systems is mainly dictated by the first-order mixing coefficient (λ), which is proportional to spin-orbit coupling (H SO ) and inversely proportional to ΔE ST . While minimizing ΔE ST has been the focus of the OLED community over the last decade, the effect of H SO in these systems is largely overlooked. Here, molecular systems with increased H SO are designed and synthesized by substituting selected heteroatoms of high-performance TADF materials with heavy-atom selenium. A new series of multicolor TADF materials with remarkable EQEs are achieved. One of these materials, SeDF-B, results in pure blue emission with EQEs approaching 20%. Additionally, flexible graphene-based electrodes are developed for OLEDs and revealed to have similar performance as standard indium tin oxide (ITO) in most cases. These devices are the first report of TADF based OLEDs that utilize graphene-based anodes.

Four novel benzo[c][1,2,5]thiadiazole comprising monomers namely 5-fluoro-6-((2-octyldodecyl)oxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (TBTT), 5-fluoro-4,7-bis(4-hexylthiophen-2-yl)-6-((2-octyldodecyl)oxy)benzo[c][1,2,5]thiadiazole (HTBTHT), 5-fluoro-4,7-di(furan-2-yl)-6-((2-octyldodecyl)oxy)benzo- [c][1,2,5]thiadiazole (FBTF), and 5-fluoro-6-((2-octyldodecyl)oxy)-4,7-bis(thieno[3,2-b]thiophen-2-yl)benzo[c][1,2,5]thiadiazole (TTBTTT) were designed, and synthesized successfully via Stille polycondensation reaction. The structural characterizations of the monomers were performed by 1H and 13C NMR spectroscopy and High Resolution Mass Spectroscopy (HRMS). The monomers were then electropolymerized in a three electrode cell system via cyclic voltammetry. The electrochemical, and spectroelectrochemical characterization of the polymers were reported in detail. Besides, theoretical calculations were performed to elucidate observed experimental properties. According to the cyclic voltammogram of the polymers, HOMO and LUMO energy levels were calculated as −5.68 eV/−3.91 eV, −5.71 eV/−3.72 eV, −5.61 eV/−4.04 eV, and −5.51 eV/−3.71 eV and the electronic band gaps were 1.77 eV, 1.99 eV, 1.57 eV, and 1.80 eV for PTBTT, PHTBTHT, PFBTF, and PTTBTTT, respectively.

More than 50 different acceptor units from the experimental literature have been modeled, analyzed, and compared by using the computationally extracted data from the density functional theory (DFT) perspective for tetramer structures in the form of (D−B−A−B) 4 (D, donor; A, acceptor; B, bridge) with fixed donor and bridge units. Comparison of dihedral angle between acceptor, donor, and bridge units, bond order, and hyperpolarizability reveals that these three structural properties have a dominant effect on the frontier electronic energy levels of the acceptor units. Systematic investigation of the structural properties has demonstrated the band gap energy dependency of the acceptor units on the planarity, conjugation, and the electron delocalization. Substitution effect, morphological alternation, and insertion of π-electron deficient atoms in A unit have also an important role to determine physical properties of the donor−acceptor conjugated polymers. This benchmark study will be beneficial for the band gap engineering and molecular design of the donor−acceptor copolymers using different acceptor units for the organic electronic applications.

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