Synthesis and Photovoltaic Properties of Quinoxaline-Based Semiconducting Polymers with Fluoro Atoms

A new accepter unit, 6,7-difluoro-2,3-dihexylquinoxaline, was prepared and utilized for the synthesis of the conjugated polymers containing electron donor-acceptor pair for OPVs. New series of copolymers with dioctyloxybenzodithiophene as the electron rich unit and 6,7-difluoro-2,3-dihexylquinoxaline as the electron deficient unit are synthesized. The solid films of poly[2,6-(4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene)-alt-5,8-(6,7-difluoro-2,3-dihexylquinoxaline)] (PBQxF) and poly[2,6-(4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene)-alt-5,8-(6,7-difluoro-2,3-dihexyl-5,8-di(thiophen-2-yl) quinoxaline)] (PBDTQxF) show absorption bands with maximum peaks at about 599 and 551 nm and the absorption onsets at 692 and 713 nm, corresponding to band gaps of 1.79 and 1.74 eV, respectively. The devices comprising PBQxF with PC71BM (1:2) showed open-circuit voltage (VOC) of 0.64 V, short-circuit current density (JSC) of 1.58 mA/cm 2 , and fill factor (FF) of 0.39, giving power conversion efficiency (PCE) of 0.39%. To obtain absorption in the longer wavelength region, thiophene units without any alkyl group are incorporated as one of the monomers in PBDTQxF, which may result in low solubility of the polymers to lead lower efficiency.

[1]  D. Moon,et al.  Polymer solar cells based on quinoxaline and dialkylthienyl substituted benzodithiophene with enhanced open circuit voltage , 2014 .

[2]  P. Chou,et al.  Prominent Short-Circuit Currents of Fluorinated Quinoxaline-Based Copolymer Solar Cells with a Power Conversion Efficiency of 8.0% , 2012 .

[3]  Trent E. Anderson,et al.  Quinoxaline-Based Semiconducting Polymers: Effect of Fluorination on the Photophysical, Thermal, and Charge Transport Properties , 2012 .

[4]  Gang Li,et al.  Synthesis of fluorinated polythienothiophene-co-benzodithiophenes and effect of fluorination on the photovoltaic properties. , 2011, Journal of the American Chemical Society.

[5]  Alan J. Heeger,et al.  A low-bandgap alternating copolymer containing the dimethylbenzimidazole moiety , 2010 .

[6]  Zhenan Bao,et al.  Tuning the Optoelectronic Properties of Vinylene-Linked Donor−Acceptor Copolymers for Organic Photovoltaics , 2010 .

[7]  F. Rosei,et al.  Highly Emissive and Electrochemically Stable Thienylene Vinylene Oligomers and Copolymers: An Unusual Effect of Alkylsulfanyl Substituents , 2010 .

[8]  Jan Fyenbo,et al.  Manufacture, integration and demonstration of polymer solar cells in a lamp for the “Lighting Africa” initiative , 2010 .

[9]  Nelson E. Coates,et al.  Bulk heterojunction solar cells with internal quantum efficiency approaching 100 , 2009 .

[10]  Ole Hagemann,et al.  A complete process for production of flexible large area polymer solar cells entirely using screen printing—First public demonstration , 2009 .

[11]  Yang Yang,et al.  Synthesis, characterization, and photovoltaic properties of a low band gap polymer based on silole-containing polythiophenes and 2,1,3-benzothiadiazole. , 2008, Journal of the American Chemical Society.

[12]  S. Jenekhe,et al.  New Didecyloxyphenylene−Acceptor Alternating Conjugated Copolymers: Synthesis, Properties, and Optoelectronic Device Applications , 2008 .

[13]  S. Xiao,et al.  Conjugated Polymers of Fused Bithiophenes with Enhanced π-Electron Delocalization for Photovoltaic Applications , 2008 .

[14]  P. Liu,et al.  Benzodithiophene Copolymer—A Low‐Temperature, Solution‐Processed High‐Performance Semiconductor for Thin‐Film Transistors , 2007 .

[15]  N. E. Coates,et al.  Efficient Tandem Polymer Solar Cells Fabricated by All-Solution Processing , 2007, Science.

[16]  Ping Liu,et al.  Synthesis and Thin-Film Transistor Performance of Poly(4,8-didodecylbenzo[1,2-b:4,5-b‘]dithiophene) , 2006 .

[17]  Christoph J. Brabec,et al.  Design Rules for Donors in Bulk‐Heterojunction Solar Cells—Towards 10 % Energy‐Conversion Efficiency , 2006 .

[18]  Y. Yamashita,et al.  New Narrow-Bandgap Polymer Composed of Benzobis(1,2,5-thiadiazole) and Thiophenes , 1995 .

[19]  G. Wegner,et al.  Steric effects in 3‐substituted polythiophenes: comparing band gap, nonlinear optical susceptibility and conductivity of poly(3‐cyclohexylthiophene) and poly(3‐hexylthiophene) , 1992 .

[20]  Soo‐Hyoung Lee,et al.  Synthesis characterization and bulk-heterojunction photovoltaic applications of new naphtho[1,2-b:5,6-b′]dithiophene–quinoxaline containing narrow band gap D–A conjugated polymers , 2014 .

[21]  J. Fréchet,et al.  Polymer-fullerene composite solar cells. , 2008, Angewandte Chemie.