Thiazole-based organic semiconductors for organic electronics

Effects of cyano (CN)-groups on the planarity, film morphology and photovoltaic performance of benzodithiophene-based polymers

A class of polymers (POT-DH, POT-HCN and POT-DCN) were synthesized and they contain the same donor (BDT) and acceptor units but different numbers of cyano (CN)-groups, i.e. 0, 1 and 2.

Solution processable benzooxadiazole and benzothiadiazole based D-A-D molecules with chalcogenophene: field effect transistor study and structure property relationship

We present here the physicochemical characterization of a series of D-A-D type molecules which comprise benzooxadiazole (BDO) and benzothiadiazole (BDT) core symmetrically linked to two aromatic-heterols (furan (F), thiophene (T) and selenophene (Se)) at 4 and 7-positions. The molecular structures of four compounds 2 (T-BDO-T), 3 (Se-BDO-Se), 5 (T-BDT-T), and 6 (Se-BDT-Se) were determined by single-crystal X-ray diffraction. The combination of chalcogen atoms of benzochalcogenadiazole and chalcogenophene in D-A-D molecules has significant impact on their molecular packing in crystal structures. Structural analyses and theoretical calculations showed that all the molecules are nearly planar. Crystal structures of 2, 3, 5, and 6 showed significant short range interactions such as π···π, CH···π, S···π, Se···π, N···H, O···H, S···H, Se···H, S···O, and Se···N interactions, which influence crystal packing and orientation of the capped aromatic-heterol rings with respect to the central BDO or BDT unit. The π-stacking interactions have been observed via intermolecular overlap of the donor with acceptor units of the adjacent molecules which facilitate the charge transport process. Good thermal stability and solubility in common organic solvents make them good candidate for flexible electronics. Interestingly, the molecules 2, 3, and 6 have the propensity to form ordered crystallites when sheared during the drying process in the thin films. Devices based on these solution processable all organic FETs demonstrated hole mobility as high as 0.08 cm(2) V(-1) s(-1) and Ion/Ioff ratio of 10(4).

Polymers for electronics and spintronics

This critical review is devoted to semiconducting and high spin polymers which are of great scientific interest in view of further development of the organic electronics and the emerging organic spintronic fields. Diversified synthetic strategies are discussed in detail leading to high molecular mass compounds showing appropriate redox (ionization potential (IP), electron affinity (EA)), electronic (charge carrier mobility, conductivity), optoelectronic (electroluminescence, photoconductivity) and magnetic (magnetization, ferromagnetic spin interactions) properties and used as active components of devices such as n- and p-channel field effect transistors, ambipolar light emitting transistors, light emitting diodes, photovoltaic cells, photodiodes, magnetic photoswitches, etc. Solution processing procedures developed with the goal of depositing highly ordered and oriented films of these polymers are also described. This is completed by the description of principal methods that are used for characterizing these macromolecular compounds both in solution and in the solid state. These involve various spectroscopic methods (UV-vis-NIR, UPS, pulse EPR), electrochemistry and spectroelectrochemistry, magnetic measurements (SQUID), and structural and morphological investigations (X-ray diffraction, STM, AFM). Finally, four classes of polymers are discussed in detail with special emphasis on the results obtained in the past three years: (i) high IP, (ii) high |EA|, (iii) low band gap and (iv) high spin ones.

Organic sensitizers from D-π-A to D-A-π-A: effect of the internal electron-withdrawing units on molecular absorption, energy levels and photovoltaic performances

The high performance and low cost of dye-sensitized solar cells (DSSCs) have drawn great interest from both academic and industrial circles. The research on exploring novel efficient sensitizers, especially on inexpensive metal-free pure organic dyes, has never been suspended. The donor-π bridge-acceptor (D-π-A) configuration is mainstream in the design of organic sensitizers due to its convenient modulation of the intramolecular charge-transfer nature. Recently, it has been found that incorporation of additional electron-withdrawing units (such as benzothiadiazole, benzotriazole, quinoxaline, phthalimide, diketopyrrolopyrrole, thienopyrazine, thiazole, triazine, cyanovinyl, cyano- and fluoro-substituted phenyl) into the π bridge as internal acceptors, termed the D-A-π-A configuration, displays several advantages such as tuning of the molecular energy levels, red-shift of the charge-transfer absorption band, and distinct improvement of photovoltaic performance and stability. We apply the D-A-π-A concept broadly to the organic sensitizers containing additional electron-withdrawing units between electron donors and acceptors. This review is projected to summarize the category of pure organic sensitizers on the basis of the D-A-π-A feature. By comparing the structure-property relationship of typical photovoltaic D-A-π-A dyes, the important guidelines in the design of such materials are highlighted.