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Recent reports on non-conjugated pendant electroactive polymers (NCPEPs) have demonstrated the significance of altering structural variables specifically the stereoregularity, the nature of the pendant group and the length of the spacer connecting that group to the backbone for tuning of their optoelectronic properties. The only synthetic approach that allows for selectively studying the effects of tuning these variables without additional superimposed effects of varied molecular weights and tacticities is the post-polymerization functionalization methodology in which parent polymers are synthesized first and then functionalized with the respective pendant groups and spacers. However, specifically for tuning of the pendant group itself, the scope of such post-polymerization functionalization methods remains largely underexplored. Here, the compatibility of the established photochemical thiol-ene post-polymerization method with various pendant groups is investigated for functionalization of stereoregular and stereorandom poly(allyl methacrylates) made via anionic polymerization using an organolithium initiator. Carbazole and a family of four 3,6-disubstituted carbazoles with phenyl, methoxy, nitrile and t -butyl substituents were investigated as the respective pendant groups. With the phenyl, methoxy and nitrile substituted pendant groups limitations of the scope of the thiol-ene methodology due to limited solubility and vulnerability to photochemical side reactions could be demonstrated. In contrast, t -butyl substituents did not impede the post-polymerization functionalization. The corresponding functionalized NCPEPs were characterized and effects of substitution of the carbazole pendant group with t -butyl groups on the optoelectronic properties of the polymers are discussed. Overall, this work demonstrates critical limitations of the thiol-ene functionalization method as well as their origin when applied to differently substituted pendant groups. [Display omitted] • The thiol-ene reaction is used for functionalization of methacrylate polymers. • Functional groups on carbazole inhibit functionalization in several cases. • The impact of photochemical and solubility limitations is discussed. • Hole mobilities improve upon annealing for both atactic and isotactic polymers. [ABSTRACT FROM AUTHOR]

Abstract We report on the strong changes induced, by confinement, in the microstructure of the semiconductor poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2- b ]thiophene) (PBTTT) and its photovoltaic blend with [6,6]-Phenyl-C71-butyric acid methyl ester (PC 71 BM). These organic compounds can be used as model systems to illustrate how sensitive this class of materials can be to spatial confinement on device-relevant length scales. The spatial confinement of nanofilaments as a function of diameter, from 180 to 25 nm, has been investigated by X-ray scattering with nanofocused synchrotron beams. The effects of spatial confinement are evident by crystallization in different crystal forms, reduction of crystallinity, phase segregation and anisotropic crystal orientation. It is also shown that confinement is an efficient tool to direct the overall texture included the crystal orientation of the homopolymer PBTTT and the PBTTT/PC 71 BM blend in a controlled manner. Graphical abstract Image 1 Highlights • Solution template wetting allows the fabrication of polymer and hybrid nanowires. • Confinement in PBTTT and PBTTT/PCBM nanowires has been studied by X-ray nanoprobes. • Confinement induces phase segregation and different crystal forms in hybrid nanowires. • Interaction of organic semiconductors with template walls directs the overall texture. [ABSTRACT FROM AUTHOR]

Effect of casting solvents on drop cast thin films of conductive conjugated polymers is largely studied by characterizing post processed films. However, the results have often been inconclusive due to the complexity of the in-situ evolution of structures. In this research we implement in-situ grazing incidence wide angle x-ray scattering (GIWAXS) approach to extracting morphological evolution information during film formation in model Poly(3-hexylthiophene) (P3HT): [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend films that have otherwise been widely studied. Casting solvents include chloroform, benzene and tetrahydrothiophene (THT), carefully selected for their relative solubilities of P3HT and PCBM. Individual casting solvent studies show that the casting solvents' solubility for P3HT and pure solvent boiling point, along with residual solvent content in the films have significant implications on final thin film morphology and crystallization of its constituent components. For example, the orientations of P3HT in P3HT:PCBM films, cast from different solvents, are largely affected by the individual solubilities of P3HT and PCBM, and substrate surface energy. On the other hand PCBM crystal growth from different PCBM solutions predominantly depends on the solubilities of PCBM in the solvents and boiling points of solvents. In this study we correlate and distinguish the drying behavior of the blend films with respect to the drying behavior of its constituent components. These results have important ramifications for controlling desired morphology for polymer electronics, such as organic photovoltaics (OPV), organic field effect transistor (OFET) and photo-detectors. [ABSTRACT FROM AUTHOR]

Studying the gelation process of conjugated optoelectronic polymers has often been employed as a means of better understanding the final morphology and assembly in active layers of organic electronic devices due to the correlation between the experimentally observed sol-gel transition and many common solution based fabrication techniques. The nature of the percolated network structures formed through the molecular assembly that occurs during this gelation directly affects device performance in conjugated polymer based active layers. Thus, precise knowledge of the evolution of structures during gelation provides crucial information that is needed to rationally improve device performance by directing the assembly during processing. Additionally, observing the effects of environmental factors such as ambient light exposure upon the gelation process will direct efforts towards improving universally overlooked facets of the typical fabrication procedure. Thus, we have conducted a series of ultra small angle and small angle neutron scattering experiments to probe the temperature-driven gelation process of the conjugated photoactive polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) in both the presence and absence of white light. Analysis of the resultant scattering data shows that the gelation process consists of the creation and steady growth of cylindrical aggregates formed by the agglomeration of free chain P3HT. Furthermore, clear differences in the gel structure and assembly between illuminated and non-illuminated gels are observed across multiple length scales, pointing towards an optically-induced variation in the gelation process. Our results indicate that simple white light exposure sharply retards the growth of conjugated polymer microstructures, which clearly suggests that ignoring illumination conditions throughout organic electronic fabrication processes risks producing inconsistent and non-reproducible active layer architectures and ultimately endangers dependable device performance. [ABSTRACT FROM AUTHOR]

Polymers using 6-(2-thienyl)-4 H -thieno[3,2- b ]indole (TTI) with high planarity were synthesized and utilized for the photovoltaics. Push-pull types of conjugated polymers ( PTTICN, PTTICNR and PTTIFR ) containing TTI as electron pushing unit and 2-pyriminecarbonitrile or 2-fluoropyrimidine as electron pulling unit were synthesized. We designed pyrimidine derivatives with strong electron-withdrawing group (C N or fluorine) for the generation of strong electron pulling property. By the combination with the electron pushing unit, the pyrimidines with strong electron pulling units will provide low highest occupied molecular orbital (HOMO) energy levels for higher open-circuit voltages ( V OC ). For the syntheses of the polymers, the electron pushing and the electron pulling units were combined by Stille coupling reaction with Pd(0)-catalyst. The polymers of PTTICN and PTTICNR with CN unit show higher V OC than the polymer with fluorine unit. The device comprising PTTICNR and PCBM (1:4) with diiodooctane (DIO) additive showed a V OC of 0.82 V, a J SC of 6.38 mA/cm 2 , and a fill factor ( FF ) of 0.53, giving a power conversion efficiency of 2.81%. [ABSTRACT FROM AUTHOR]

Abstract: This feature article presents a short review of the recent developments in the synthesis of conjugated polyelectrolytes (CPEs) along with their applications in organic optoelectronic devices with particular focus on the molecular structures of CPEs with ionic functionality, synthetic approaches, and their utilization as an interfacial layer. The orthogonal solubility of the CPEs allows the simple preparation of multilayer organic devices by solution casting on top of a nonpolar organic photoactive layer without disturbing the interfaces, showing their effectiveness in tuning the electronic structures at the interfaces for improving the charge carrier transport and resulting device properties. These achievements highlight the dynamic nature of CPEs and their applicability to a wide range of optoelectronic devices. [Copyright &y& Elsevier]

Abstract: Considerable interest exists in the development of novel n-type conjugated polymers, since many currently available polymer systems have insufficient electron mobility and/or electron affinity. In this work, a universal synthesis route is presented towards a new class of n-type conjugated polymers, i.e. poly(p-fluoranthene vinylene) (PFV) and its derivatives. This route is illustrated with three examples, i.e. unsubstituted PFV and functionalized hexyl-PFV and dodecyl-PFV. All polymers have been synthesized via the dithiocarbamate precursor route. Solubility was introduced by incorporation of alkyl side chains, which leads to a significantly enhanced purity and processability as compared to unsubstituted PFV. Under the applied electrochemical conditions PFV-type polymers demonstrate typical n-type behavior. Additional CELIV mobility measurements on dodecyl-PFV reveal an excellent electron mobility, μe =1.4×10−4 cm2/Vs. Hence, poly(p-fluoranthene vinylene) and its derivatives are promising n-type materials for organic optoelectronic applications. [Copyright &y& Elsevier]

The expansion of the field of organic electronics has hinged upon structural and fundamental developments in the field of conjugated polymers. Conjugated polymers allow for the manufacture of low-cost, light-weight, flexible organic electronic devices, with notable applications in organic photovoltaics (OPV), organic field effect transistors (OFET), and organic light emitting diodes (OLED). This extraordinary breadth of applications is due to the remarkable diversity of structure, an extensive understanding of structure-function relationships, and the relative ease of structural tuning. Important advancements and the development of such applications is largely due to the evolution of polymer structure, enabled by a broad range of synthetic methods for the tailoring of structures and the development of improved polymerization conditions to limit defects. This perspective provides background from the early days of concerted and focused conjugated polymer research (1970s-1990) to the present, and describes how the tailoring of conjugated polymer structure has now become closely tied to application. A significant focus is also directed to how polymerization methods have evolved from the aggressive, unselective conditions used for oxidative polymerizations to finely tuned transition-metal catalyzed polymerizations that can provide incredibly high structural-fidelity and can proceed through C–H activation. Areas for future work and emerging areas are also discussed, such as high-performing polymers without added structural and synthetic complexity, identifying polymer structures with improved environmental stability, flexible and transient or bioresorbable conjugated polymers, mixed-ion conductors, and photocatalytic and select biological applications. Image 1 • A perspective on the field of conjugated polymers is presented. • The development of evolution of conjugated polymer architecture is described. • The relationship between conjugated polymer structure and application is presented. [ABSTRACT FROM AUTHOR]