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n-Doped conjugated polymers usually show low electrical conductivities and low thermoelectric power factors, limiting their applications in n-type organic thermoelectrics. Here, we report the synthesis of a new diketopyrrolopyrrole (DPP) derivative, pyrazine-flanked DPP (PzDPP), with the deepest LUMO level in all the reported DPP derivatives. Based on PzDPP, a donor−acceptor copolymer, P(PzDPP-CT2), is synthesized. The polymer displays a deep LUMO energy level and strong interchain interaction with a short π−π stacking distance of 3.38 Å. When doped with n-dopant N-DMBI, P(PzDPP-CT2) exhibits high ntype electrical conductivities of up to 8.4 S cm −1 and power factors of up to 57.3 μW m −1 K −2 . These values are much higher than previously reported n-doped DPP polymers, and the power factor also ranks the highest in solution-processable n-doped conjugated polymers. These results suggest that PzDPP is a promising high-performance building block for n-type organic thermoelectrics and also highlight that, without sacrificing polymer interchain interactions, efficient n-doping can be realized in conjugated polymers with careful molecular engineering.

Molecular doping is a powerful method to fine-tune the thermoelectric properties of organic semiconductors, in particular to impart the requisite electrical conductivity. The incorporation of molecular dopants can, however, perturb the microstructure of semicrystalline organic semiconductors, which complicates the development of a detailed understanding of structure-property relationships. To better understand how the doping pathway and the resulting dopant counterion influence the thermoelectric performance and transport properties, a new dimer dopant, (N-DMBI) 2 , is developed. Subsequently, FBDPPV is then n-doped with dimer dopants (N-DMBI) 2 , (RuCp*mes) 2 , and the hydride-donor dopant N-DMBI-H. By comparing the UV-vis-NIR absorption spectra and morphological characteristics of the doped polymers, it is found that not only the doping mechanism, but also the shape of the counterion strongly influence the thermoelectric properties and transport characteristics. (N-DMBI) 2 , which is a direct electron-donating dopant with a comparatively small, relatively planar counterion, gives the best power factor among the three systems studied here. Additionally, temperature-dependent conductivity and Seebeck coefficient measurements differ between the three dopants with (N-DMBI) 2 yielding the best thermoelectric properties.

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A simple method for facile synthesis of three-dimensional (3D) bismuth oxyhalide (BiOX, X═Cl, Br, I) hierarchical structures at room temperature has been developed. Under the influence of L-lysine surfactant, the bismuth and halogen (Cl, Br, I) sources hydrolyze and self-assemble into flower-like hierarchical architectures within 10 min. The resulted materials were characterized by XRD, FESEM, TEM, UV-vis DRS, and N2 adsorption-desorption techniques. We found that l-lysine is indispensable for their formation and the amount of HX has great effect on the final morphology. The BiOX (X═Cl, Br, I) hierarchical architectures are composed of single-crystalline nanoplates. We propose an amino-and-carboxyl structure-directing mechanism for the formation of the hierarchical structures. To evaluate the photocatalytic activity of the as-prepared materials, rhodamine-B was employed as a probe dye for degradation under visible light. All of the BiOX (X═Cl, Br, I) with 3D architectures show higher photocatalytic activities than their sheet-like counterparts. The superior activity is ascribed to the better light-harvesting capacity of the 3D hierarchical structures. The adopted method can be applied for large-scale generation of novel structures of similar kinds in a facile manner.

Doping has been widely used to control the charge carrier concentration in organic semiconductors. However, in conjugated polymers, n-doping is often limited by the tradeoff between doping efficiency and charge carrier mobilities, since dopants often randomly distribute within polymers, leading to significant structural and energetic disorder. Here, we screen a large number of polymer building block combinations and explore the possibility of designing n-type conjugated polymers with good tolerance to dopant-induced disorder. We show that a carefully designed conjugated polymer with a single dominant planar backbone conformation, high torsional barrier at each dihedral angle, and zigzag backbone curvature is highly dopable and can tolerate dopant-induced disorder. With these features, the designed diketopyrrolopyrrole (DPP)-based polymer can be efficiently n-doped and exhibit high n-type electrical conductivities over 120 S cm−1, much higher than the reference polymers with similar chemical structures. This work provides a polymer design concept for highly dopable and highly conductive polymeric semiconductors.

BN-embedded polycyclic aromatic hydrocarbons (PAHs) with unique optoelectronic properties are underdeveloped relative to their carbonaceous counterparts due to the lack of suitable and facile synthetic methods. Moreover, the dearth of electron-deficient BN-embedded PAHs further hinders their application in organic electronics. Here we present the first facile synthesis of novel perylene diimide derivatives (B2N2-PDIs) featuring n-type B–N covalent bonds. The structures of these compounds are fully confirmed through the detailed characterizations with NMR, MS, and X-ray crystallography. Further investigation shows that the introduction of BN units significantly modifies the photophysical and electronic properties of these B2N2-PDIs and is further understood with the aid of theoretical calculations. Compared with the parent perylene diimides (PDIs), B2N2-PDIs exhibit deeper highest occupied molecular orbital energy levels, new absorption peaks in the high-energy region, hypsochromic shift of absorption and emission maxima, and decrement of photoluminescent quantum yields. Single-crystal field-effect transistors based on B2N2-PDIs showcase an electron mobility up to 0.35 cm2 V–1 s–1, demonstrating their potential application in optoelectronic materials.

Doping of polymeric semiconductors limits the miscibility between polymers and dopants.A lthough significant efforts have been devoted to enhancing miscibility through chemical modification, the electrical conductivities of n-doped polymeric semiconductors are usually below1 0Scm À1 .W e report adifferent approach to overcome the miscibility issue by modulating the solution-state aggregates of conjugated polymers.Wefound that the solution-state aggregates of conjugated polymers not only changed with solvent and temperature but also changed with solution aging time.M odulating the solution-state polymer aggregates can directly influence their solid-state microstructures and miscibility with dopants.A s ar esult, both high doping efficiency and high charge-carrier mobility were simultaneously obtained. The n-doped electrical conductivity of P(PzDPP-CT2) can be tuned up to 32.1 Scm À1 .T his method can also be used to improve the doping efficiency of other polymer systems (e.g. N2200) with different aggregation tendencies and behaviors.