Donor–acceptor alternating π‐conjugated polymers containing Di(thiophen‐2‐yl)pyrene and 2,5‐Bis(2‐octyldodecyl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione for organic thin‐film transistors

New diketopyrrolopyrrole (DPP)‐containing conjugated polymers such as poly(2,5‐bis(2‐octyldodecyl)‐3‐(5‐(pyren‐1‐yl)thiophen‐2‐yl)‐6‐(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione) (P(DTDPP‐alt‐(1,6)PY)) and poly(2,5‐bis(2‐octyldodecyl)‐3‐(5‐(pyren‐2‐yl)thiophen‐2‐yl)‐6‐(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione) (P(DTDPP‐alt‐(2,7)PY)) were successfully synthesized via Suzuki coupling reactions under Pd(0)‐catalyzed conditions. P(DTDPP‐alt‐(2,7)PY), incorporating 2,5‐bis(2‐octyldodecyl)‐3,6‐di(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione (DTDPP) at the 2,7‐position of a pyrene ring showed a lower band‐gap energy (E. = 1.65 eV) than the 1,6‐substituted analog, P(DTDPP‐alt‐(1,6)PY) (E = 1.71 eV). The energies of the molecular frontier orbitals of the substituted polymers were successfully tuned by changing the anchoring position of DTDPP from the 1,6‐ to the 2,7‐position of the pyrene ring. An organic thin‐film transistor fabricated using the newly synthesized P(DTDPP‐alt‐(2,7)PY), as a semiconductor material exhibited a maximum mobility of up to 0.23 cm² V^?1 s^?1 (I_on/off ～ 10⁶), which was much larger than that obtained using P(DTDPP‐alt‐(1,6)PY). This distinction is attributed to morphological differences in the solid state arising from differences between the geometrical configurations of DTDPP and the pyrene ring. In addition, the organic phototransistor devices made of P(DTDPP‐alt‐(2,7)PY) showed interesting photoinduced enhancement of drain current when irradiating the excitation light whose intensity is very small. Based on the photoinduced effect on I_DS, photocontrolled memory could be realized under the variation of gate voltages. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis and Photovoltaic Properties of Thieno[3,4‐c]pyrrole‐4,6‐dione‐based donor–acceptor Copolymers

Three donor–acceptor (D–A) 1,3‐di(thien‐2‐yl)thieno [3,4‐c]pyrrole‐4,6‐dione‐based copolymers, poly{9,9‐dioctylfluorene‐2,7‐diyl‐alt‐1,3‐bis(4‐hexylthien‐2‐yl)‐5‐octylthieno[3,4‐c]pyrrole‐4,6‐dione}, poly{N‐(1‐octylnonyl)carbazole‐2,7‐diyl‐alt‐1,3‐bis(4‐hexylthien‐2‐yl)‐5‐octylthieno[3,4‐c]pyrrole‐4,6‐dione}, and poly {4,8‐bis(2‐ethylhexyloxyl) benzo[1,2‐b:3,4‐b′]dithiophene‐alt‐1,3‐bis(4‐hexylthien‐2‐yl)‐5‐octylthieno[3,4‐c] pyrrole‐4,6‐dione} were synthesized by Suzuki or Stille coupling reaction. By changing the donor segment, the bandgaps and energy levels of these copolymers could be finely tuned. Cyclic voltammetric study shows that the highest occupied molecular orbital (HOMO) energy levels of the three copolymers are deep‐lying, which implies that these copolymers have good stability in the air and the relatively low HOMO energy level assures a higher open‐circuit potential when they are used in photovoltaic cells. Bulk‐heterojunction photovoltaic cells were fabricated with these polymers as the donors and PC₇₁BM as the acceptor. The cells based on the three copolymers exhibited power conversion efficiencies of 0.22, 0.74, and 3.11% with large open‐circuit potential of 1.01, 0.99, and 0.90 V under one sun of AM 1.5 solar simulator illumination (100 mW/cm²). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Diketopyrrolopyrrole‐based liquid crystalline conjugated donor–acceptor copolymers with reduced band gap for polymer solar cells

A new liquid crystalline (LC) acceptor monomer 2,5‐bis[4‐(4′‐cyanobiphenyloxy)dodecyl]‐3,6‐dithiophen‐2‐yl‐pyrrolo[3,4‐c]pyrrole‐1,4‐dione (TDPPcbp) was synthesized by incorporating cyanobiphenyl mesogens into diketopyrrolopyrrole (DPP). The monomer was copolymerized with bis(2‐ethylhexyloxy)benzo[1,2‐b:4,5‐b′] dithiophene (BDT) and N‐9′‐heptadecanylcarbazole (CB) donors to obtain donor–acceptor alternating copolymers poly[4,8‐bis(2‐ethylhexyloxy)benzo[1,2‐b:4,5‐b′]dithiophene‐alt‐3,6‐bis(thiophen‐5‐yl)‐2,5‐bis[4‐(4′‐cyanobiphenyloxy)dodecyl]‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione] (PBDTDPPcbp) and poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐3,6‐bis(thiophen‐5‐yl)‐2,5‐bis[4‐(4′‐cyano‐biphenyloxy)dodecyl]‐2,5‐dihydropyrrolo[3, 4‐c]pyrrole‐1,4‐dione] (PCBTDPPcpb) with reduced band gap, respectively. The LC properties of the copolymers, the effects of main chain variation on molecular packing, optical properties, and energy levels were analyzed. Incorporating the mesogen cyanobiphenyl units not only help polymer donors to pack well through mesogen self‐organization but also push the fullerene acceptor to form optimized phase separation. The bulk heterojunction photovoltaicdevicesshow enhanced performance of 1.3% for PBDTDPPcbp and 1.2% for PCBTDPPcbp after thermal annealing. The results indicate that mesogen‐controlled self‐organization is an efficient approach to develop well‐defined morphology and to improve the device performance. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Syntheses and Characterization of 4-Octyloxybenzyl Substituted Diketopyrrolopyrrole-based Red Emitting Copolymers with Low Turn-on Voltage

Two novel diketopyrrolopyrrole-based alternating copolymers, poly(2,7-(9,9-diethyl)-fluorenylvinylene-alt-2,5-bis(4′-octyloxyphe- nylmethyl)-3,6-bis(4-vinylenephenyl)pyrrolo[3,4-c]pyrrole-1,4-dione) (P1) and poly(1,4-(2,5-dioctyl- oxy)-phenylenevinylene-alt-2,5-bis(4′-octyloxyphenylmethyl)-3,6-bis(4-vinylenephenyl)pyrrolo[3,4-c]pyrrole-1,4-dione) (P2) were synthesized through Wittig polycondensation in good yields. P1 and P2 were characterized by NMR, FT-IR, UV-Vis, photoluminescence (PL) and electroluminescence (EL). EL devices with ITO/PEDOT/polymer/CsF/Al exhibited red-emitting light with the maximum EL wavelength at 620 nm and 682 nm. The results show that PL quantum yield of the polymers in thin film can be improved through N-alkylation of diketopyrrolopyrrole (DPP) with bulky substituent. EL performance of P2 was better than P1, which might be due to 1,4-dioctyloxybenzene of P2 enhancing the hole-transporting to make more charge balance. EL devices of P1 and P2 possessed low turn on voltage (2.4 V and 2.1 V, respectively), which was an advantage for PLED.     

Synthesis of new polyfluorene copolymers with a comonomer containing triphenylamine units and their applications in white‐light‐emitting diodes

Novel conjugated polyfluorene copolymers, poly[9,9‐dihexylfluorene‐2,7‐diyl‐co‐(2,5‐bis(4′‐diphenylaminostyryl)‐phenylene‐1,4‐diyl)]s (PGs), have been synthesized by nickel(0)‐mediated polymerization from 2,7‐dibromo‐9,9‐dihexylfluorene and 1,4′‐dibromo‐2,5‐bis(4‐diphenylaminostyryl)benzene with various molar ratios of the monomers. Because of the incorporation of triphenylamine (TPA) moieties, PGs exhibit much higher HOMO levels than the corresponding polyfluorene homopolymers and are able to facilitate hole injection into the polymer layer from the anode electrode in light‐emitting diodes. Conventional polymeric light‐emitting devices with the configuration ITO/PEDOT:PSS/polymer/Ca/Al have been fabricated. A light‐emitting device produced with one of the PG copolymers (PG10) as the emitting layer exhibited a voltage‐independent and stable bluish‐green emission with color coordinates of (0.22, 0.42) at 5 V. The maximum brightness and current efficiency of the PG10 device were 3370 cd/m² (at 9.6 V) and 0.6 cd/A, respectively. To realize a white polymeric light‐emitting diode, PG10 as the host material was blended with 1.0 wt % of a red‐light‐emitting polymer, poly[9,9‐dioctylfluorene‐2,7‐diyl‐alt‐2,5‐bis(2‐thienyl‐2‐cyanovinyl)‐1‐(2′‐ethylhexyloxy)‐4‐methoxybenzene‐5′,5′‐diyl] (PFR4‐S), and poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV). The device based on PG10:PFR4‐S showed an almost perfect pure white electroluminescence emission, with Commission Internationale de l'Eclairage (CIE) coordinates of (0.33, 0.36) at 8 V; for the PG10:MEH‐PPV device, the CIE coordinates at this voltage were (0.30, 0.40) with a maximum brightness of 1930 cd/m². Moreover, the white‐light emission from the PG10:PFR4‐S device was stable even at different driving voltages and had CIE coordinates of (0.34, 0.36) at 6 V and (0.31, 0.35) at 10 V. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1199–1209, 2007     

Synthesis of novel π‐conjugating polymers based on dibenzothiophene

Novel π‐conjugating polymers based on dibenzothiophene were synthesized with a novel dibenzothiophene derivative, 2,8‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)dibenzothiophene ( 1 ), prepared from dibenzothiophene. The Suzuki coupling polycondensation of 1 with 2,7‐dibromo‐9,9‐dioctylfluorene, 3,6‐dibromo‐9‐octylcarbazole, or 1,4‐dibromo‐2,5‐dioctyloxybenzene afforded the corresponding dibenzothiophene‐based polymers. The measurements of photoluminescence indicated that all these polymers exhibited blue emission in solution. The copolymer containing dibenzothiophene and 9,9‐dioctylfluorene units exhibited higher thermal stability than poly[(9,9‐dioctylfluorene‐2,7‐diyl)], although the quantum yield of copolymer was lower than that of poly[(9,9‐dioctylfluorene‐2,7‐diyl)]. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1521–1526, 2003     

New photoluminescent conjugated polymers with 1,4‐dioxo‐3,6‐diphenylpyrrolo[3,4‐c]pyrrole (DPP) and 1,4‐phenylene units in the main chain

A series of π‐conjugated polymers and copolymers containing 1,4‐dioxo‐3,6‐diphenylpyrrolo[3,4‐c]pyrrole (also known as 2,5‐dihydro‐3,6‐diphenylpyrrolo[3,4‐c]pyrrole‐1,4‐dione) (DPP) and 1,4‐phenylene units in the main chain is described. The polymers are synthesised using the palladium‐catalysed aryl‐aryl coupling reaction (Suzuki coupling) of 2,5‐dihexylbenzene‐1,4‐diboronic acid with 1,4‐dioxo‐2,5‐dihexyl‐3,6‐di(4‐bromophenyl)pyrrolo[3,4‐c]pyrrole and 1,4‐dibromo‐2,5‐dihexylbenzene in different molar ratios. Soluble hairy rod‐type polymers with molecular weights up to 21 000 are obtained. Polymer solutions in common organic solvents such as chloroform or xylene are of orange colour (λ_max = 488 nm) and show strong photoluminescence (λ_max = 544 nm). The photochemical stability is found to be higher than for corresponding saturated polymers containing isolated DPP units in the main chain. Good solubility and processability into thin films render the compounds suitable for electronic applications.     

Synthesis and characterization of thiazolothiazole‐based polymers and their applications in polymer solar cells

A novel series of thiazolothiazole (Tz)‐based copolymers, poly[9,9‐didecylfluorene‐2,7‐diyl‐alt‐2,5‐bis‐(3‐hexylthiophene‐2‐yl)thiazolo[5,4‐d]thiazole] (P1), poly[9,9‐dioctyldibenzosilole‐2,7‐diyl‐alt‐2,5‐bis‐(3‐hexylthiophene‐2‐yl)thiazolo[5,4‐d]thiazole] (P2), and poly[4,4′‐bis(2‐ethylhexyl)‐dithieno[3,2‐b:2′,3′‐d]silole‐alt‐2,5‐bis‐(3‐hexylthiophene‐2‐yl)thiazolo[5,4‐d]thiazole] (P3), were synthesized for the use as donor materials in polymer solar cells (PSCs). The field‐effect carrier mobilities and the optical, electrochemical, and photovoltaic properties of the copolymers were investigated. The results suggest that the donor units in the copolymers significantly influenced the band gap, electronic energy levels, carrier mobilities, and photovoltaic properties of the copolymers. The band gaps of the copolymers were in the range of 1.80–2.14 eV. Under optimized conditions, the Tz‐based polymers showed power conversion efficiencies (PCEs) for the PSCs in the range of 2.23–2.75% under AM 1.5 illumination (100 mW/cm²). Among the three copolymers, P1, which contained a fluorene donor unit, showed a PCE of 2.75% with a short‐circuit current of 8.12 mA/cm², open circuit voltage of 0.86 V, and a fill factor (FF) of 0.39, under AM 1.5 illumination (100 mW/cm²). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Poly(1,4‐diketo‐3,6‐diphenylpyrrolo[3,4‐c]pyrrole‐alt−3,6‐carbazole/2,7‐fluorene) as high‐performance two‐photon dyes

This article reports the synthesis, one‐ and two‐photon absorption, and excited fluorescence properties of poly(1,4‐diketo‐3,6‐diphenylpyrrolo[3,4‐c]pyrrole‐alt‐N‐octyl‐3,6‐carbazole/2,7‐fluorene) ( PDCZ / PDFL ). PDCZ and PDFL are synthesized by the Suzuki cross‐coupling of 2,5‐dioctyl‐1,4‐diketo‐3,6‐bis(p‐bromophenylpyrrolo[3,4‐c]pyrrole and N‐octyl‐3,6‐bis(3,3‐dimethyl‐1,3,2‐dioxaborolan‐2‐yl)carbazole or 2,7‐bis(3,3‐dimethyl‐1,3,2‐dioxaborolan‐2‐yl)fluorene and have number‐average molecular weights of 8.5 × 10³ and 1.14 × 10⁴ g/mol and polydispersities of 2.06 and 1.83, respectively. They are highly soluble in common organic solvents and emit strong orange one‐ and two‐photon excited fluorescence (2PEF) in THF solution and exhibit high light and heat stability. The maximal two‐photon absorption cross‐sections (δ) measured in THF solution by the 2PEF method using femtosecond laser pulses are 970 and 900 GM per repeating unit for PDCZ and PDFL , respectively. These 1,4‐diketo‐pyrrolo[3,4‐c]pyrrole‐containing polymers with full aromatic structure and large δ will be promising high‐performance 2PA dyes applicable in two‐photon science and technology. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 944–951     

Siloles and Acetenyl Aromatics Copolymers: Synthesis,Characterization and Photophysical Properties

Two copolymers, poly(1,1‐dimethyl‐3,4‐diphenylsilole‐alt‐N‐hexyl‐3,6‐diethynylcarbazole) (PS‐DyCz) and poly(1,1‐dimethyl‐3,4‐diphenylsilole‐alt‐2,7‐diethynyl‐9,9′‐dihexylfluorene) (PS‐DyF), were synthesized by Sonogashira coupling reaction of 2,5‐dibromo‐1,1‐dimethyl‐3,4‐diphenylsilole and N‐hexyl‐3,6‐diethynylcarbazole or 2,7‐diethynyl‐9,9′‐dihexylfluorene, respectively. The chemical structures of the copolymers were characterized by NMR, FT‐IR techniques. Their thermal and photophysical properties were evaluated by TGA, DSC, UV‐Vis and fluorescence spectroscopy, respectively. The weight‐averaged molecular weights (M_w) of PS‐DyCz and PS‐DyF are 1.20×10⁴ and 3.83×10⁴ Da, respectively. The degree of polymerization is 8 and 22 units. These π‐conjugated polymers exhibited lower band‐gap of 2.25 and 2.70 eV due to the presence of silole rings and C?C triple bonds in their backbone, the results were consistent with the density functional (DFT) calculations at the B3LYP/6‐31G* level.     

Effects of Block Length in Copolymers Based on Regioregular Oligothiophenes Linked With Electron‐Accepting Units

Copolymers with an alternating structure of regioregular oligo(3‐hexylthiophene) (O3HT) with different lengths and 2,5‐dibutyl‐3,6‐di(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione (DPP) were synthesized through Stille coupling reaction. The light absorption of the copolymers can be rationally tuned to have a broad spectrum across the visible region by adjusting the length of O3HT. Organic solar cells fabricated with the copolymers and PCBM showed a broad photoresponse and a comparable efficiency to that of poly(3‐hexylthiophene) (P3HT):PCBM cells. The external quantum efficiency and fluorescence spectra suggested that the intrachain energy transfer from the O3HT block to the vicinity of the DPP unit could limit the photovoltaic performance of the copolymers.     

Bipyridinophane‐containing conjugated polymers modulated with an intramolecular aromatic C?H/π interaction

Bipyridinophane–fluorene conjugated copolymers have been synthesized via Suzuki and Heck coupling reactions from 5,8‐dibromo‐2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane and suitable fluorene precursors. Poly[2,7‐(9,9‐dihexylfluorene)‐co‐alt‐5,8‐(2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane)] ( P7 ) exhibits large absorption and emission redshifts of 20 and 34 nm, respectively, with respect to its planar reference polymer Poly[2,7‐(9,9‐dihexylfluorene)‐co‐alt‐1,4‐(2,5‐dimethylbenzene)] ( P11 ), which bears the same polymer backbone as P7 . These spectral shifts originate from intramolecular aromatic C? H/π interactions, which are evidenced by ultraviolet–visible and ¹H NMR spectra as well as X‐ray single‐crystal structural analysis. However, the effect of the intramolecular aromatic C? H/π interactions on the spectral shift in poly[9,9‐dihexylfluorene‐2,7‐yleneethynylene‐co‐alt‐5,8‐(2,11‐dithia[3]paracyclo[3](4,4′)‐2,2′‐bipyridinophane)] ( P10 ) is much weaker. Most interestingly, the quenching behaviors of these two conjugated polymers are largely dependent on the polymer backbone. For example, the fluorescence of P7 is efficiently quenched by Cu²⁺, Co²⁺, Ni²⁺, Zn²⁺, Mn²⁺, and Ag⁺ ions. In contrast, only Cu²⁺, Co²⁺, and Ni²⁺ ions can partially quench the fluorescence of P10 , but much less efficiently than the fluorescence of P7 . The static Stern–Volmer quenching constants of Cu²⁺, Co²⁺, and Ni²⁺ ions toward P7 are of the order of 10⁶ M^?1, being 1300, 2500, and 37,300 times larger than those of P10 , respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4154–4164, 2006     

Simple synthesis,photophysics, and electroluminescent properties of poly[2,7‐bis(4‐tert‐butylstyryl)fluorene‐9, 9‐diyl‐alt‐alkane‐α,ω‐diyl]

A simple synthetic route was used for the synthesis of a novel series of alternating copolymers based on substituted 2,7‐distyrylfluorene bridged through alkylene chains. First, 2,7‐dibromofluorene was reacted with 2 equiv of butyllithium, and this was followed by a treatment with 1 equiv of α,ω‐dibromoalkane to yield the intermediate, poly(2,7‐dibromofluorene‐9,9‐diyl‐alt‐alkane‐α,ω‐diyl). ( 1 ) Heck coupling of the latter with 1‐tert‐butyl‐4‐vinylbenzene afforded the target, poly[2,7‐bis(4‐tert‐butylstyryl)fluorene‐9,9‐diyl‐alt‐alkane‐α,ω‐diyl] ( 2 ). The two versions of 2 ( 2a and 2b which have hexane and decane, respectively, as alkane groups) were readily soluble in common organic solvents. Their glass‐transition temperature was relatively low (52 and 87 °C). An intense blue photoluminescence emission with maxima at about 408 and 409 nm was observed in tetrahydrofuran solutions, whereas thin films exhibited an orange emission with maxima at 569 and 588 nm. Very large redshifts of the photoluminescence maxima and Stokes shifts in thin films indicated strong aggregation in the solid state. Both polymers oxidized and reduced irreversibly. Single‐layer light‐emitting diodes with hole‐injecting indium tin oxide and electron‐injecting aluminum electrodes were fabricated. They emitted orange light with external electroluminescence efficiencies of 0.52 and 0.36% photon/electron, as determined in light‐emitting diodes made of 2a and 2b , with alkylenes of (CH₂)₆ and (CH₂)₁₀, respectively. An increase in the external electroluminescence efficiency up to 1.5% was reached in light‐emitting diodes made of polymer blends consisting of 2a and poly(9,9‐dihexadecylfluorene‐2,7‐diyl), which emitted blue‐white light. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 809–821, 2007.     

Incorporation of fluorene‐based emitting polymers into silica

Novel polyfluorene copolymers with pendant hydroxyl groups, poly[2,7‐(9,9‐dihexylfluorene)‐2,7‐(9,9‐bis(6‐hydroxyhexyl)fluorene)‐co‐2,7‐(9,9‐dihexylfluorene)‐1,4‐phenylene] (PFP‐OH) and poly[2,7‐(9,9‐dihexylfluorene)‐2,7‐(9,9‐bis(6‐hydroxyhexyl)fluorene)‐co‐2,7‐(9,9‐dihexylfluorene)‐4,7‐(2,1,3‐benzothiadiazole)] (PFBT‐OH) were prepared. Acid‐catalyzed polycondensations of tetraethoxysilane were carried out in the presence of these polymers to obtain homogeneous hybrids. Photoluminescence spectra of these hybrids suggested the polymers were immobilized in silica matrix retaining their π‐conjugated structures. Further, hybrids of coat film were prepared utilizing perhydropolysilazane as a silica precursor. Their optical properties were examined. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis and characterization of diphenylaminodiphenyl stryl based alternating copolymers

Diphenylaminobiphenylated stryl based alternating copolymers with phenyl or fluorene, which were expected to have a terphenylene vinylene backbone containing an (N,N‐diphenylamino)biphenyl pendant and a phenyl/fluorene/phenylene vinylene backbone containing an (N,N‐diphenylamino)biphenyl pendant, were synthesized by a Suzuki coupling reaction. The obtained copolymers were confirmed with various types of spectroscopy. The alternating copolymers showed good hole‐injection properties because of their low oxidation potential and good solubility and high thermal stability with a high glass‐transition temperature. The alternating copolymers showed blue emissions because of the adjusted conjugation lengths; the maximum wavelength was 460 nm for poly{4,4′‐biphenylene‐α‐[4″‐(N,N′‐diphenylamino)diphenyl]vinylene‐alt‐5‐(2′‐ethylhexyloxy)‐2‐methoxybenzene} and 487 nm for poly{4,4′‐biphenylene‐α‐[4″‐(N,N′‐diphenylamino)diphenyl] vinylene‐alt‐9,9‐dihexylfluorene}. The maximum brightness of indium tin oxide/poly(3,4‐ethylene dioxythiophene)/polymer/LiF/Al devices with poly{4,4′‐biphenylene‐α‐[4″‐(N,N′‐diphenylamino)diphenyl]vinylene‐alt‐5‐(2′‐ethylhexyloxy)‐2‐methoxybenzene} or poly{4,4′‐biphenylene‐α‐[4″‐(N,N′‐diphenylamino)diphenyl]vinylene‐alt‐9,9‐dihexylfluorene} as the emitting layer was 250 or 1000 cd/m², respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 341–347, 2007     

Effect of backbone structures on photovoltaic properties in naphthodithiophene‐based copolymers

A “zigzag” naphthodithiophene‐based copolymer, poly[4,9‐bis(2‐ethylhexyloxy)naphtho[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl‐alt‐1,3‐(5‐heptadecan‐9‐yl)‐4H‐thieno[3,4‐c]pyrrole‐4,6‐dione] (P1) is synthesized and its properties are compared to “linear” naphthodithiophene‐based copolymer, poly[4,9‐bis(2‐ethylhexyloxy)naphtho[2,3‐b:6,7‐d′]dithiophene‐2,7‐diyl‐alt‐1,3‐(5‐heptadecan‐9‐yl)‐4H‐thieno[3,4‐c]pyrrole‐4,6‐dione] (P2). The field‐effect carrier mobilities and the optical, electrochemical, and photovoltaic properties of the copolymers are systematically investigated. The results suggest that the backbone of the copolymer structure significantly influences the band gap, electronic energy levels, carrier mobilities, and photovoltaic properties of the resultant thin films. In this work, the zigzag naphtho[1,2‐b:5,6‐b′]dithiophene‐based copolymer displays a good hole mobility and a high open‐circuit voltage; however, polymer solar cells in which the linear naphtho[2,3‐b;6,7‐d′]dithiophene‐based copolymer is used as the electron donor material perform better than the cells prepared using the zigzag naphtho[1,2‐b:5,6‐b′]dithiophene‐based copolymer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 305–312     

Preparation of new π‐conjugated polypyrroles by organometallic polycondensations. Synthesis of N‐BOC (t‐butoxycarbonyl) and N‐phenylethynyl polymers,thermal deprotection of the BOC Group,and packing structure of the N‐phenylethynyl polymer

New π–conjugated polypyrroles such as poly(3‐heptyl‐N‐(t‐butoxycarbonyl)pyrrole‐2,5‐diyl), PPr(3‐Hep; N‐BOC) , and poly(N‐(phenylethynyl)pyrrole‐2,5‐diyl‐alt‐thiophene‐2,5‐diyl), Copoly‐2 , were prepared by organometallic polycondensations using the corresponding 2.5‐dihalopyrroles as the starting materials. Deprotection of the BOC group of PPr(3‐Hep; N‐BOC) proceeded at 185 °C to give poly(3‐heptylpyrrole). XRD (X‐ray diffraction) data of Copoly‐2 indicated that Copoly‐2 assumed a stacked structure in the solid. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6223–6232, 2005     

Arylamino‐functionalized fluorene‐ and carbazole‐based copolymers: Color‐tuning their CdTe nanocrystal composites from red to white

Four alternating arylamino‐functionalized copolymers were synthesized in a Suzuki copolymerization applying 4, 4′‐(2,7‐dibromo‐9H‐fluorene‐9,9‐diyl)dianiline, 4,4′‐(2,7‐dibromo‐9H‐fluorene‐9,9‐diyl)bis(N,N‐diphenylaniline), 4‐(3,6‐dibromo‐9H‐ carbazol‐9‐yl)aniline and 4‐(3,6‐dibromo‐9H‐carbazol‐9‐yl)‐N,N‐diphenylaniline in combination with 2,2′‐(9,9‐dioctyl‐9H‐fluorene‐2,7‐diyl)bis(1,3,2‐dioxaborinane). The resulting novel alternating copolymers were fully characterized. The copolymers revealed blue light emission and wide optical bandgaps of at least 2.93 eV for the fluorene‐based and 3.07 eV for the carbazole‐based polymers. The amino‐functions allow to tie semiconducting CdTe nanocrystals (NCs) and to synthesize a series of composites with CdTe NCs. Moreover, tuning the emission color over a wide range by tying these CdTe NCs results in a facile preparation of organic–inorganic semiconductor composites with emission colors “à la carte.” © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and Photovoltaic Properties of Cyclopentadithiophene‐Based Low‐Bandgap Copolymers That Contain Electron‐Withdrawing Thiazole Derivatives

We have synthesized four types of cyclopentadithiophene (CDT)‐based low‐bandgap copolymers, poly[{4,4‐bis(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene‐2,6‐diyl}‐alt‐(2,2′‐bithiazole‐5,5′‐diyl)] ( PehCDT‐BT ), poly[(4,4‐dioctyl‐4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene‐2,6‐diyl)‐alt‐(2,2′‐bithiazole‐5,5′‐diyl)] ( PocCDT‐BT ), poly[{4,4‐bis(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene‐2,6‐diyl}‐alt‐{2,5‐di(thiophen‐2‐yl)thiazolo[5,4‐d]thiazole‐5,5′‐diyl}] ( PehCDT‐TZ ), and poly[(4,4‐dioctyl‐4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene‐2,6‐diyl)‐alt‐{2,5‐di(thiophen‐2‐yl)thiazolo[5,4‐d]thiazole‐5,5′‐diyl}] ( PocCDT‐TZ ), for use in photovoltaic applications. The intramolecular charge‐transfer interaction between the electron‐sufficient CDT unit and electron‐deficient bithiazole (BT) or thiazolothiazole (TZ) units in the polymeric backbone induced a low bandgap and broad absorption that covered 300 nm to 700–800 nm. The optical bandgap was measured to be around 1.9 eV for PehCDT‐BT and PocCDT‐BT , and around 1.8 eV for PehCDT‐TZ and PocCDT‐TZ . Gel permeation chromatography showed that number‐average molecular weights ranged from 8000 to 14 000 g mol^?1. Field‐effect mobility measurements showed hole mobility of 10^?6–10^?4 cm² V^?1 s^?1 for the copolymers. The film morphology of the bulk heterojunction mixtures with [6,6]phenyl‐C₆₁‐butyric acid methyl ester (PCBM) was also examined by atomic force microscopy before and after heat treatment. When the polymers were blended with PCBM, PehCDT‐TZ exhibited the best performance with an open circuit voltage of 0.69 V, short‐circuit current of 7.14 mA cm^?2, and power conversion efficiency of 2.23 % under air mass (AM) 1.5 global (1.5 G) illumination conditions (100 mW cm^?2).     

Quantifying the role of interfacial width on intermolecular charge recombination in block copolymer photovoltaics

Block copolymers have the potential to control the interfacial and mesoscopic structure in the active layer of organic photovoltaics and consequently enhance device performance beyond systems which rely on physical mixtures. When utilized as the active layer, poly(3‐hexylthiophene‐2,5‐diyl)‐block‐poly((9,9‐bis‐(2‐octyldodecyl)fluorene‐2,7‐diyl)‐alt‐(4,7‐di(thiophene‐2‐yl)?2,1,3‐benzothiadiazole)?5′,5″‐diyl) donor–acceptor block copolymers have recently demonstrated 3% power conversion efficiencies in devices. Nevertheless, the role of the interfacial structure on charge transfer processes remains unclear. Using density functional theory, we examined charge transfer rate constants in model interfaces of donor–acceptor block copolymers. Our results demonstrate that intermolecular charge recombination can depend on the interfacial breadth, where sharp interfaces (ca. 1 nm) suppress intermolecular charge recombination by orders of magnitude. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1224–1230