Intrinsic traps in organic semiconductors can be eliminated by trap-filling with F4-TCNQ. Photovoltaic tests show that devices with F4-TCNQ at parts per thousand concentration outperform control devices due to an improved fill factor. Further studies confirm the trap-filling pathway and demonstrate the general nature of this finding.

A series of five thionated naphthalene diimides (NDIs) with linear alkyl chains was synthesized and the optoelectronic, self-assembly, and device properties were studied. When tested in organic thin-film transistors, the electron mobilities of the thionated derivatives are three orders of magnitude higher than the non-thionated parent analogue, with the highest mobility measured for cis-S2 (µ max = 7.5 × 10 -2 cm 2 V -1 s -1 ). In contrast to branched chain PDIs and NDIs, the electron mobility does not increase appreciably with degree of thionation, and the average mobilities are quite consistent ranging from 3.9 × 10 -2 to 7.4 × 10 -2 cm 2 V -1 s -1 for one to three sulfurs.18 been previously reported for the compound. 37 This discrepancy may be due to slight differences in device configuration and fabrication conditions, or in compound purity. The S3 device annealed at 150 o C also showed no performance, possibly due to the lower thermal stability of the higher thionated compounds (vide supra). Devices could not be prepared from trans-S2 or S4 due to their poor solubility and film-forming ability.

An unexpected morphology comprising patchy nanofibers can be accessed from the self-assembly of an all-conjugated, polyselenophene-block-polythiophene copolymer. This morphology consists of very small (<10 nm), polythiophene- and polyselenophene-rich domains and is unprecedented for both conjugated polymers and diblock copolymers in general. We propose that the patchy morphology occurs from the enhanced miscibility of the blocks arising from the longer alkyl chains in comparison to similar block copolymers with shorter alkyl chains, which fully phase separate, as well as the difference in rigidity between the polythiophene and polyselenophene blocks. This work demonstrates a facile way to tune the self-assembly behavior of conjugated block copolymers by modification of the side chain substituents.

Conjugated block copolymers, where each block contains a unique electroactive group, allows selective block-oxidation in solution, which promotes reversible, redox-controlled self-assembly.

Understanding self-assembly behavior and resulting morphologies in block co-polymer films is an essential aspect of chemistry and materials science. Although the self-assembly of amorphous coil−coil block co-polymers is relatively well understood, that of semicrystalline block co-polymers where each block has distinct crystallization properties remains unclear.Here, we report a detailed study to elucidate the rich selfassembly behavior of conjugated thiophene−selenophene (P3AT-b-P3AS) block co-polymers. Using a combination of microscopy and synchrotron-based X-ray techniques, we show that three different film morphologies, denoted as lamellae, cocrystallized fibers, and patchy fibers, arise from the self-assembly of these block co-polymers over a relatively narrow range of overall degrees of polymerization (30 < N < 90). Crystallization-driven phase separation occurs at a very low N (<35), and lamellar films are formed. Conversely, at medium N (50−60) and high N (>80), the thiophene and selenophene blocks cocrystallize into nanofibers, where medium N leads to much more mixing than high N. The overall tendency for phase separation in these systems follows rather different trends than phase separation in amorphous polymers in that we observe the greatest degree of phase separation at the lowest N. Finally, we demonstrate how each morphology influences transport properties in organic thin-film transistors comprised of these conjugated polymers.

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G raphene is a two-dimensional sheet of sp 2 hybridized carbon atoms. It has been extensively studied due to its

Heavy atom main group element-containing conjugated polymers have attracted increasing attention in recent years. The synthesis of these compounds is generally involved, and little is known about their optoelectronic device performance. Here we examine the relationship between polymer structure and optoelectronic behavior in a series of chalcogenophene homopolymers of thiophene, selenophene, and tellurophene with well-matched molecular weights, dispersity, and regioregularity. We employ fast and slow drying device preparations to study the effect of polymer–fullerene separation on charge separation and collection in canonical bulk heterojunction photovoltaic cells. In both preparations, increasing heteroatom size leads to larger proportions of finely mixed polymer–fullerene domains. Differences in polymer–fullerene separation between preparations result in the formation of optimal morphologies in selenophene and tellurophene devices with little impact on thiophene devices. We then use planar heterojunction devices to directly examine the effects of heteroatom substitution on charge transport and charge generation and find that in the absence of polymer–fullerene mixing, devices exhibit similar diode behavior. We further demonstrate that ultrafast decay pathways unique to heavy heteroatom-containing polymers are apparent in both planar and bulk heterojunctions and thus not dependent on polymer–fullerene mixing or polymer assembly. This work directly examines the role of heteroatom substitution in defining the photovoltaic performance of conjugated homopolymers. Through single-atom substitution we are able to significantly modify polymer assembly, mixing, and optoelectronic properties. Specific emphasis on tellurophene polymers reveals relationships between polymer structure and properties that are not apparent in more traditional light-atom chalcogenophenes such as thiophene and selenophene.