Efficient Free Triplet Generation Follows Singlet Fission in Diketo-pyrrolopyrrole Polymorphs with Goldilocks Coupling.

Microcrystal electron diffraction, grazing incidence wide-angle scattering, and UV-Vis spectroscopy were used to determine the unit cell structure and the relative composition of dimethylated diketopyrrolopyrrole (MeDPP) H- and J-polymorphs within thin films subjected to vapor solvent annealing (VSA) for different times. Electronic structure and excited state deactivation pathways of the different polymorphs were examined by transient absorption spectroscopy, conductive probe atomic force microscopy, and molecular modeling. We find VSA initially converts amorphous films into mixtures of H- and J-polymorphs and promotes further conversion from H to J with longer VSA times. Though both polymorphs exhibit efficient SF to form coupled triplets, free triplet yields are higher in J-polymorph films compared to mixed films because coupling in J-aggregates is lower, and, in turn, more favorable for triplet decoupling.

Crystal structure and orientation of organic semiconductor thin films by microcrystal electron diffraction and grazing-incidence wide-angle X-ray scattering.

We use microcrystal electron diffraction (MicroED) to determine structures of three organic semiconductors, and show that these structures can be used along with grazing-incidence wide-angle X-ray scattering (GIWAXS) to understand crystal packing and orientation in thin films. Together these complimentary techniques provide unique structural insights into organic semiconductor thin films, a class of materials whose device properties and electronic behavior are sensitively dependent on solid-state order.

Correction: Visible-light photooxidation in water by 1O2-generating supramolecular hydrogels.

[This corrects the article DOI: 10.1039/C9SC06481H.].

Photoactive organic material discovery with combinatorial supramolecular assembly.

Organic semiconductors have received substantial attention as active components in optoelectronic devices because of their processability and customizable properties. Tailoring the organic active layer in these devices to exhibit the desired optoelectronic properties requires understanding the complex and often subtle structure-property relationships governing their photophysical response to light. Both structural organization and molecular orbitals play pivotal roles, and their interactions with each other are difficult to anticipate based upon the structure of the components alone, especially in systems comprised of multiple components. In pursuit of design rules, there is a need to explore multicomponent systems combinatorially to access larger data sets, and supramolecularly to use error correcting, noncovalent assembly to achieve long-range order. This review will focus on the use of supramolecular chemistry to study combinatorial, hierarchical organic systems with emergent optoelectronic properties. Specifically, we will describe systems that undergo excited state deactivation by charge transfer (CT), singlet fission (SF), and Förster resonance energy transfer (FRET). Adopting combinatorial, supramolecular assembly to study emergent photophysics promises to rapidly accelerate progress in this research field.