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A new pentacyclic building block, benzodibenzofuranquinone (BDBFQ), is synthesized in a single step from the inexpensive and readily available feedstocks chloranil and 3-bromophenol. This versatile repeat unit is incorporated into a series of conjugated materials as either the redox active quinone form or as an electron-rich dialkylated benzodibenzofuran (BDBF) unit. To illustrate the performance that can be obtained from these systems, optical and electrochemical properties were studied via UV–vis–NIR spectroscopy and cyclic voltammetry. Thin-film morphology was characterized via grazing incidence wide-angle X-ray scattering with thin-film field-effect transistor measurements further demonstrating the utility of this system. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017

We synthesized two new thieno[3,4-c]pyrrole-4,6-dione (TPD)- and diketopyrrolopyrrole (DPP)-based small molecules having pyridine end groups, TPDTPy and DPPTPy, using the Stille and Suzuki coupling reactions, respectively. The optical, electrochemical, and photovoltaic properties of these small molecules depended on the introduced electron-accepting units of TPD and DPP. DPPTPy exhibited a relatively low-energy bandgap (Eg) of 1.82 eV compared to TPDTPy (2.22 eV) because of the stronger electron-withdrawing ability of DPP compared to TPD. Organic photovoltaic cells with the inverted ITO/ZnO/small molecule:(6,6)-phenyl-C71-butyric acid methyl ester/MoO3/Ag structure were fabricated. The DPPTPy-based device showed a relatively high power conversion efficiency of 0.62% compared to TPDTPy (0.16%), mainly because of the red-shifted UV absorption, lower Eg, and the higher short-circuit current of DPPTPy.

T.L. and Y.E. contributed equally to this work. This work was financially supported by the Korea Institute of Energy Technology Evaluation & Planning (KETEP) and the Ministry of Trade, Industry & Energy (No. 20173010012960) and by the National Research Foundation of Korea (NRF) Grant funded by the Ministry of Science & ICT (NRF-2015R1A1A3A04001498 & NRF-2019R1A2C1003679) of the Republic of Korea.

Two novel organic–inorganic hybrid polyfluorene derivatives, poly{(9,9′-dioctyl-2,7-fluorene)-co-(9,9′-di-POSS-2,7-fluorene)-co-[2,5-bis(octyloxy)-1,4-phenylene]} (PFDOPPOSS) and poly{(9,9′-dioctyl-2,7-fluorene)-co-(9,9′-di-POSS-2,7-fluorene)-co-bithiophene} (PFT2POSS), were synthesized by the Pd-catalyzed Suzuki reaction of polyhedral oligomeric silsesquioxane (POSS) appended fluorene, dioctyl phenylene, and bithiophene moieties. The synthesized polymers were characterized with 1H NMR spectroscopy and elemental analysis. Photoluminescence (PL) studies showed that the incorporation of the POSS pendant into the polyfluorene derivatives significantly enhanced the fluorescence quantum yields of the polymer films, likely via a reduction in the degree of interchain interaction as well as keto formation. Additionally, the blue-light-emitting polyfluorene derivative PFDOPPOSS showed high thermal color stability in PL. Moreover, single-layer light-emitting diode devices of an indium tin oxide/poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)/polymer/Ca/Al configuration fabricated with PFDOPPOSS and PFT2POSS showed much improved brightness, maximum luminescence intensity, and quantum efficiency in comparison with devices fabricated with the corresponding pristine polymers PFDOP and PFT2. In particular, the maximum external quantum efficiency of PFT2POSS was 0.13%, which was twice that of PFT2 (0.06%), and the maximum current efficiency of PFT2POSS was 0.38 cd/A, which again was twice that of PFT2 (0.19 cd/A). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2943–2954, 2006

A series of fluorene-thiophene-based semiconducting materials, poly(9,9'-dioctylfluorene-alt-α,α'-bisthieno[3,2-b]thiophene) (F8TT2), poly(9,9'-di(3,6-dioxaheptyl) fluorene-alt-thieno[3,2-b]thiophene) (BDOHF8TT), poly(9,9'-di(3,6-dioxaheptyl)fluorene-alt-bithiophene) (BDOHF8T2), and poly(9,9'-dioctylfluorene-co-bithiophene-co-[4-(2-ethylhexyloxyl)phenyl]diphenylamine) (F8T2TPA), was synthesized through a palladium-catalyzed Suzuki coupling reaction. F8TT2, BDOHF8TT, BDOHF8T2, and F8T2TPA films exhibited photoluminescence maxima at 523, 550, 522, and 559 nm, respectively. Solution-processed field-effect transistors (FETs) fabricated with all the copolymers except F8T2TPA showed p-type organic FET characteristics. Studies of the differential scanning calorimetry scans and FETs of the polymers revealed that more crystalline polymers gave better FET device performance. The greater planarity and rigidity of thieno[3,2-b]thiophene in comparison with bithiophene resulted in higher crystallinity of the polymer backbone, which led to improved FET performance. On the other hand, the random incorporation of the triphenylamine moiety into F8T2TPA caused the polymer chains to lose crystallinity, resulting in an absence of FET characteristics. With this study, we could assess the liquid-crystallinity dependence of the field-effect carrier mobility on organic FETs based on liquid-crystalline copolymers.

New electroluminescent polymers (poly(9,9′-dioctylfluorene-co-thieno[3,2-b]thiophene-co-benzo[2,3,5]thiadiazole) (P1) and poly(9,9′-dioctylfluorene-co-thieno[3,2-b]thiophene-co-benzo[2,3,5]thiadiazole-co-[4-(2-ethylhexyloxyl)phenyl]diphenylamine (P2)) possess hole-transporting or electron-transporting units or both in the main chains. Electron-deficient benzothiadiazole and electron-rich triphenylamine moieties were incorporated into the polymer backbone to improve the electron-transporting and hole-transporting characteristics, respectively. P1 and P2 show greater solubility than poly(9,9′-dioctylfluorene-co-thieno[3,2-b]thiophene (PFTT), without sacrificing their good thermal stability. Moreover, owing to the incorporation of the electron-deficient benzothiadiazole unit, P1 and P2 exhibit remarkably lower LUMO levels than PFTT, and thus, it should facilitate the electron injection into the polymer layer from the cathode electrode. Consequently, because of the balance of charge mobility, LED devices based on P1 and P2 exhibit greater brightness and efficiency (up to 3000 cd/m2 and 1.35 cd/A) than devices that use the pristine PFTT. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 243–253, 2006