Search

We synthesized a novel low‐band‐gap, conjugated polymer, poly[4,7‐bis(3′,3′‐diheptyl‐3,4‐propylenedioxythienyl)‐2,1,3‐benzothiadiazole] [poly(heptyl4‐PTBT)], consisting of alternating electron‐rich, diheptyl‐substituted propylene dioxythiophene and electron‐deficient 2,1,3‐benzothiadiazole units, and its photovoltaic properties were investigated. A thin film of poly(heptyl4‐PTBT) exhibited an optical band gap of 1.55 eV. A bulk‐heterojunction solar cell with indium tin oxide/poly(3,4‐ethylenedioxythiophene)/poly(heptyl4‐PTBT): methanofullerene [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) (1:4)/LiF/Al was fabricated with poly(heptyl4‐PTBT) as an electron donor and PCBM as an electron acceptor and showed an open‐circuit voltage, short‐circuit current density, and power conversion efficiency of 0.37 V, 3.15 mA/cm2, and 0.35% under air mass 1.5 (AM1.5G) illumination (100 mW/cm2), respectively. A solid‐state, dye‐sensitized solar cell with a SnO2:F/TiO2/N3 dye/poly(heptyl4‐PTBT)/Pt device was fabricated with poly(heptyl4‐PTBT) as a hole‐transport material. This device exhibited a high power conversion efficiency of 3.1%, which is the highest power conversion efficiency value with hole‐transport materials in dye‐sensitized solar cells to date. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1394–1402, 2007 [ABSTRACT FROM AUTHOR]

ABSTRACT The synthesis of donor-acceptor type semiconducting copolymers is described. Quinoxaline (QX) or difluorinated quinoxaline (DFQX) derivatives serve as electron acceptors, while thiophene (T) or selenophene (Se) serve as electron donors. Alternating polymers are synthesized through Stille cross-coupling, and their thermal stability, optical and electrochemical properties, field-effect carrier mobilities, film crystallinities, and photovoltaic performances are investigated. The intramolecular charge transfer between the electron-donating and electron-accepting units in the backbone induces absorption from 450 to 750 nm. The optical band-gap energies of the polymers are between 1.65 and 1.73 eV, and depend on the polymer structure. Organic photovoltaic cells fabricated using a polymer composed of DFQX and selenophene (PSe-DFQX) exhibit a power conversion efficiency of 5.14% with an open-circuit voltage of 0.78 V, a short-circuit current density of 11.71 mA/cm2, and fill factor of 0.57 under AM 1.5 G irradiation (100 mW cm−2). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1904-1914 [ABSTRACT FROM AUTHOR]

ABSTRACT Two donor-acceptor conjugated polymers, PTSSO-TT and PTSSO-BDT, composed of acenaphtho[1,2-c]thiophene -S,S-dioxide (TSSO) as a new electron acceptor and thienothiophene (TT) or benzo[1,2-b:4,5-b']dithiophene (BDT) as electron donors, were synthesized with Stille cross-coupling reactions. The number-averaged molecular weights ( Mn) of PTSSO-TT and PTSSO-BDT were found to be 15100 and 26000 Da, with dispersity of 1.8 and 2.4, respectively. The band-gap energies of PTSSO-TT and PTSSO-BDT are 1.56 and 1.59 eV, respectively. The HOMO levels of PTSSO-TT and PTSSO-BDT are −5.4 and −5.5 eV, respectively. These results indicate that the inclusion of TSSO accepting units into polymers is a very effective method for lowering their HOMO energy levels. The field-effect mobilities of PTSSO-TT and PTSSO-BDT were determined to be 1.5 × 10−3 and 4.5 × 10−4 cm2 V−1 s−1, respectively. A polymer solar cell device prepared with PTSSO-TT as the active layer was found to exhibit a power conversion efficiency (PCE) of 3.79% with an open circuit voltage of 0.71 V under AM 1.5 G (100 mW cm−2) conditions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 498-506 [ABSTRACT FROM AUTHOR]

ABSTRACT 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 [ABSTRACT FROM AUTHOR]

ABSTRACT A series of new donor-acceptor-type low-band-gap semiconducting polymers were synthesized as electron donors for organic photovoltaic cells. The polymers comprised quinoxaline derivatives as the acceptors and a benzodithiophene (BDT) derivative as the donors. 5,8-Dibromoquinoxaline (Qx), 8,11-dibromobenzo[a]phenazine (BPz), 10,13-dibromodibenzo[a,c]phenazine (DBPz), and 8,11-dibromo-5-(9H-carbazol-9-yl)benzo[a]phenazine) (CBPz) were synthesized and polymerized with 2,6-bis(trimethyltin)−4,8-diethylhexyloxybenzo-[1,2-b;3,4-b]dithiophene (BDT) through Stille cross-coupling to produce four types of fully conjugated semiconducting polymers: PBDT-Qx, PBDT-BPz, PBDT-DBPz, and PBDT-CBPz, respectively. Intramolecular charge transfer between the electron donating and accepting units in the polymeric backbone induced a broad absorption from 300 to 800 nm. The optical band gap energies of the polymers were measured from their absorption onsets to be 1.54-1.80 eV depending on the polymer structure. Solution-processed field-effect transistors were fabricated to measure the hole mobilities of the polymers, and bulk hetero-junction photovoltaic devices were fabricated using the synthesized polymers as electron donors and fullerene derivatives as electron acceptors. One of these devices showed a high power conversion efficiency of 3.87% with an open-circuit voltage of 0.78 V, a short-circuit current of 9.68 mA/cm2, and a fill factor of 0.51 under air mass 1.5 global (AM 1.5 G) illumination conditions (100 mW/cm2). © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4136-4149 [ABSTRACT FROM AUTHOR]

A new carbazole-based electron accepting unit, 5-(2,7-dibromo-9H-carbazol-9-yl)benzo[ a]phenazine (CBP), was newly designed and synthesized as the acceptor part of donor-acceptor type low band-gap polymers for polymer solar cells. The CBP was copolymerized with electron donating monomers such as benzo[1,2-b:4,5-b′]dithiophene (BDT) or 4,8- bis(2-octyl-2-thienyl)-benzo[1,2-b:4,5-b′]dithiophene (BDTT) through Stille cross-coupling polymerization, and produced two alternating copolymers, PBDT-CBP and PBDTT-CBP. An alternating copolymer (PBDT-CBZ) consisted of 2,7-dibromo-9-(heptadecan-9-yl)-9H-carbazole (CBZ) and BDT units was also synthesized for comparison. PBDT-CBZ showed the maximum absorption at 430 nm and did not show absorption at wavelengths longer than 513 nm. However, CBP containing polymers (PBDT-CBP and PBDTT-CBP) showed a broad absorption between 300 and 850 nm due to the intramolecular charge transfer interaction between the electron donating and accepting blocks in the polymeric backbone. Bulk heterojunction photovoltaic devices were fabricated using the synthesized polymers as electron donors and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) as electron acceptor. One of these devices showed a power conversion efficiency of 2.33%, with an open-circuit voltage of 0.81 V, a short-circuit current of 6.97 mA/cm2, and a fill factor (FF) of 0.41 under air mass (AM) 1.5 global (1.5 G) illumination conditions (100 mW/cm2). © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013, 51, 2354-2365 [ABSTRACT FROM AUTHOR]

A set of novel conjugated polyfluorene co- polymers, poly[(9,9′-didecylfluorene-2,7-diyl)- co-(4,7′-di-2-thienyl- 2′,1′,3′-benzothiadiazole-5,5-diyl)- co-(pyrene-1,6-diyl)], are synthesized via Pd(II)-mediated polymerization from 2,7-bis(4′,4′,5′, 5′-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9′-di- n-decylfluorene, 4, 7-di(2-bromothien-5-yl)-2,1,3-benzothiadiazole, and 1,6-dibromopyrene with a variety of monomer molar ratios. The field-effect carrier mobilities and optical, electrochemical, and photovoltaic properties of the copolymers are systematically investigated. The hole mobilities of the copolymers are found to be in the range 7.0 × 10−5 − 8.0 × 10−4 cm2 V−1 s−1 and the on/off ratios were 8 × 103 − 7 × 104. Conventional polymer solar cells (PSCs) with the configuration ITO/PEDOT:PSS/polymer:PC71BM/LiF/Al are fabricated. Under optimized conditions, the polymers display power conversion efficiencies (PCEs) for the PSCs in the range 1.99-3.37% under AM 1.5 illumination (100 mW cm−2). Among the four copolymers, P2, containing a 2.5 mol % pyrene component incorporated into poly[9,9′-didecylfluorene-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PFDTBT) displays a PCE of 3.37% with a short circuit current of 9.15 mA cm−2, an open circuit voltage of 0.86 V, and a fill factor of 0.43, under AM 1.5 illumination (100 mW cm−2). © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 [ABSTRACT FROM AUTHOR]

Three new polymers poly(3,4′′′-didodecyl) hexaselenophene) (P6S), poly(5,5′-bis(4,4′-didodecyl-2,2′-biselenophene-5-yl)-2,2′-biselenophene) (HHP6S), and poly(5,5′-bis(3′,4-didodecyl-2,2′-biselenophene-5-yl)-2,2′-biselenophene) (TTP6S) that have the same selenophene-based polymer backbone but different side chain patterns were designed and synthesized. The weight-averaged molecular weights ( Mw) of P6S, HHP6S, and TTP6S were found to be 19,100, 24,100, and 19,700 with polydispersity indices of 2.77, 1.48, and 1.41, respectively. The UV-visible absorption maxima of P6S, HHP6S, and TTP6S are at 524, 489, and 513 nm, respectively, in solution and at 569, 517, and 606 nm, respectively, in the film state. The polymers P6S, HHP6S, and TTP6S exhibit low band gaps of 1.74, 1.95, and 1.58 eV, respectively. The field-effect mobilities of P6S, HHP6S, and TTP6S were measured to be 1.3 × 10−4, 3.9 × 10−6, and 3.2 × 10−4 cm2 V−1 s−1, respectively. A photovoltaic device with a TTP6S/[6,6]-phenyl C71-butyric acid methyl ester (1:3, w/w) blend film active layer was found to exhibit an open circuit voltage ( VOC) of 0.71 V, a short circuit current ( JSC) of 5.72 mA cm−2, a fill factor of 0.41, and a power conversion efficiency (PCE) of 1.67% under AM 1.5 G (100 mW cm−2) illumination. TTP6S has the most planar backbone of the tested polymers, which results in strong π-π interchain interactions and strong aggregation, leading to broad absorption, high mobility, a low band gap, and the highest PCE. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 [ABSTRACT FROM AUTHOR]

Condensation copolymerization reactions of carbazole 3,6-diboronate with 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole (DTBT) only produce low-molecular-weight donor (D)-π-acceptor (A) copolymers. High-molecular-weight copolymers for use in optoelectronic devices are necessary for achieving extended π-conjugation and for controlling the copolymer processibility. To elucidate the cause of the persistently low molecular weight, we synthesized three 3,6-carbazole-based D-A copolymers using copolymerizations of N-9′-heptadecanyl-3,6-carbazole with DTBT, N-9′{2-[2-(2-methoxy-ethoxy)-ethoxy]-ethyl}-3,-6-carbazole with DTBT, and N-9′-heptadecanyl-3,6-carbazole with alkyl-substituted DTBT. We investigated several parameters for their influence on molecular copolymer weight, including the conformation of the chain during growth, the solubility of the monomers, and the dihedral angles between the donor and acceptor units. Size exclusion chromatography, UV-vis absorption spectroscopy, and computational studies revealed that the low molecular weights of 3,6-carbazole-based D-A copolymers resulted from conjugation breaks and the resulting high coplanarity, which led to strong interactions between polymer chains. These interactions limited formation of high-molecular-weight-copolymers during copolymerization. The strong intermolecular interactions of the 3,6-carbazole moiety were exploited by incorporating 3,6-carbazole units into poly[9′,9′-dioctyl-2,7-flourene- alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] prepared from 9′,9′-dioctyl-2,7-flourene and DTBT. Interestingly, the number average molecular weight increased gradually with increasing 2,7-fluorene monomer content but the number of conjugation breaks was a range of 6-7. The hole mobilities of the copolymers were studied for comparison purposes. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 [ABSTRACT FROM AUTHOR]

Polymer solar cells (PSCs) were fabricated using a ternary blend film consisting two conjugated polymers and a soluble fullerene derivative as the donor and acceptor materials, respectively. And, to compare ternary blend system, the single-component copolymers consisting of the repeating units of each of the copolymers, used in ternary blend solar cells, were designed and synthesized for use as the electron donor materials in binary blend solar cells. We systematically investigated the field-effect carrier mobilities and the optical, electrochemical, and photovoltaic properties of the copolymers. Under optimized conditions, the binary blend polymer systems showed power conversion efficiencies (PCEs) for the PSCs in the range 3.87-4.16% under AM 1.5 illumination (100 mW cm−2). All polymers exhibited similar PCEs that did not depend on the ratio of repeating units. The binary blend solar cell containing a single-component copolymer as the electron donor material performed better than the ternary blend solar cell in this work. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]