Two novel conjugated donor–acceptor copolymers P1 and P2 based on acylbenzotrithiophene derivatives were prepared under Stille reaction conditions. Molecular weights of the polymers were determined by gel permeation chromatography. Thermal properties were studied by TGA and DSC methods, while optical and electrochemical properties were studied by UV spectroscopy and cyclic voltammetry. Effect of different fullerene derivatives PC 60 BM and PC 70 BM on photovoltaic characteristics was also studied.

Синтезированы четыре новых чередующихся узкозонных сополимера на основе бензодитиофена в условиях реакции Стилле. Все сополимеры обнаруживают хорошую растворимость в обычных органических растворителях и широкую абсорбцию в видимой области солнечного света по сравнению с гомополимерами бензодитиофена. Ширина запрещенной зоны полимерных пленок, полученная из вольтамперометрических данных, варьируется в пределах 1.34–2.28 эВ, а положение высшей занятой молекулярной орбитали в интервале 4.99–5.72 эВ. Напряжение холостого хода и эффективность полимерных солнечных фотоэлементов на основе синтезированных сополимеров лежат в интервале 0.22–0.65 В и 0.02–0.48% соответственно.

A power conversion efficiency of about 5.26% has been achieved for the device based onP1:PC71BM.

Two new alternating low band gap D-A copolymers with different acceptor structures of 4,8-bis-(5-bromothiophene-2-yl)-benzo[1,2,5]thiadiazole (P1) and 4,8-dithiophene-2-yl-benzo[1,2-c;4,5-c']-bis-[1,2,5]thiadiazole (P2) and a common BDT donor segment have been synthesized under Stille reaction conditions and characterized. The polymers showed good solubility, broad absorption bands and optical band gaps of 1.62 eV and 1.16 eV for P1 and P2, respectively. Bulk heterojunction (BHJ) polymer solar cells based on P1 and P2 as electron donors and fullerene derivatives (PC60BM and PC70BM) as acceptor were fabricated and their photovoltaic response was investigated. The overall power conversion efficieny (PCE) achieved for BHJ solar cells based on P1:PC60BM, P2:PC60BM, P1:PC70BM and P2:PC70BM blends cast from THF solvent is about 2.17%, 0.80%, 3.45% and 1.19%, respectively. The higher PCE for the device based on P1 has been attributed to the high value of hole mobility for P1 as compared to P2 and a larger driving force i.e. LUMO-LUMO offset, for photo-induced charge transfer for P1:PCBM BHJ active layer. The PCE has been further increased up to 5.30% and 1.58% for P1:PC70BM and P2:PC70BM blends cast from DIO/THF solvent, which is attributed to the improved crystallinity and a more balanced charge transport in the device.

Four new alternating narrow-band-gap copolymers based on benzodithiophene are synthesized under conditions of the Stille reaction. In comparison to benzodithiophene homopolymers, all these copolymers show good solubility in common organic solvents and broad absorption in the visible spectrum of sunlight. The band gaps of the polymer films, as estimated from the cyclic voltammetry data, vary within 1.34–2.28 eV, and the position of the highest occupied molecular orbital lies in the range 4.99–5.72 eV. The values of the open-circuit voltage and the efficiency of polymer solar cells based on the copolymers are within 0.22–0.65 V and 0.02–0.48%, respectively.

In the present study four new low band gap alternating donor-acceptor copolymers based on benzotrithiophene were synthesized under Stille reaction conditions. All polymers show good solubility in common organic solvents and a broad absorption in the visible region of the solar spectrum. The band gap of polymer films and HOMO levels of polymers were obtained from the voltammograms and vary in the range 1.4-2.4 eV and -5.0 - 5.4 eV, respectively. Open circuit voltage and efficiency of the developed polymer solar cells are in the range 0.33-0.57 V and 0.01-0.14 %, respectively.

Two new donor-acceptor (D-A) low band gap conjugated copolymers P1 and P2 containing different electron acceptor functional groups i.e. thienodithiadiazole (P1) and thienopyrazine (P2) derivatives were synthesized by Suzuki polycondensation reaction and characterized using H-1 NMR and gel-permeation chromatography. The optical and electrochemical properties of these copolymers were investigated. Both copolymers have a good solubility, high thermal stability, broad absorption region from 350 to 950 nm, a relatively low HOMO energy in the range of -5.28 eV for P1 and -5.25 eV for P2 and a narrow optical band gap 1.32 and 1.46 eV, respectively. Photovoltaic devices based on a mixture of the P2:PC60BM (1:3 (w/w)) at AM1.5 illumination of 100 mW cm(-2) show the over all power conversion efficiency (PCE) of 0.74% with a short-circuit current (J(sc)) of 2.28 mA cm(-2), open circuit voltage (V-oc) of 0.72 V and fill factor (FF) of 0.45, whereas P1:PC60BM showed PCE of 0.43% with a J(sc) of 1.54 mA cm(-2), V-oc, of 0.70 V and FF of 0.40. These results suggest that the thienopyrazine functional groups are attractive electron-withdrawing building blocks in conjugated D-A copolymers and can be used as electron donors for bulk heterojunction solar cells along with fullerene derivatives as electron acceptors. (C) 2013 Elsevier B.V. All rights reserved.

A new alternating copolymer P comprising of benzo[1,2-b;4,5,b']dithiophene (BDT) derivative and 4,9-bis-(5-bromothiophene-2-yl)-6,7-di-(2-ethylhexyl)[1,2,5]thiadiazolo[3,4-g]quinoxaline (DTQx) derivative electron, donating and electron withdrawing units, respectively, has been synthesized by Stille reaction. The copolymer was characterized by TGA, UV-visible absorption and cyclic voltammetry. The optical band gap of P was calculated from the onset wavelength of absorption to be about 1.38 eV. The copolymer P was used as electron donor along with PC60BM or PC70BM as electron acceptors for the fabrication of bulk heterojunction solar cells with configurations of ITO/PEDOT:PSS/P:PC60BM or PC70BM/Al. The power conversion efficiencies (PCE) of the copolymer solar cells blended with PC60BM and PC70BM as electron acceptors, spin cast from THF solvent, were 2.10% and 3.26%, respectively. The PCE device based on the P:PC70BM blend processed from DIO/THF was enhanced up to 4.47%. After optimizing the device parameters, such as blend ratio of P to PCBM and the choice of processing solvent, power conversion efficiency reaches as high as 5.12% for P:PC70BM blend, when processed from DIO/THF solvent, a blend ratio of 1 : 2 w/w and DMSO doped PEDOT:PSS buffer layer is used.

Four new alternating narrow band-gap copolymers containing benzodithiophene, 4,8-dithiophen-2-yl-benzo[1,2-c;4,5-c′-bis[1,2,5]thiadiazole, 4,9-bis(thiophen-2-yl)-6,7-di(2-ethylhexyl)-[1,2,5]thiadiazolo[3,4-g]quinoxaline, 5,8-dibromo-2,3-bis(5-octylthiophen-2-yl)quinoxaline, and 4,7-bis(5-bromothiophen-2-yl)benzo[1,2,5] thiadiazole units are synthesized under Stille reaction conditions. The structures, molecular masses, and physical properties of the copolymers are studied via 1H NMR spectroscopy, GPC, cyclic voltammetry, and thermomechanical and thermogravimetric analyses. The polymers show solubility and a broad absorption region (with the band gap in the range from 0.81 to 1.53 eV). All of the polymers are photostable in air, and their levels of the highest occupied molecular orbital vary from −4.98 to −5.30 eV. Polymer solar cells based on these copolymers as donors and fullerene PC60BM as an acceptor show open-circuit voltages in the range 0.16–0.61 V, and the efficiencies of the devices are in the range 0.02–0.49%.

Two new donor-acceptor narrow-band-gap photovoltaic copolymers containing various electron-acceptor functional groups, such as thienopyrazine and thienodithiazole derivatives, are synthesized under the conditions of the Suzuki polycondensation reaction and characterized via 1H NMR spectroscopy and GPC. The optical, electrochemical, and photovoltaic properties of the polymers are examined in detail. Both copolymers have good solubilities, high thermal stabilities, broad absorption regions (350–950 nm), relatively low levels of the highest occupied molecular orbital (−5.01 and −5.02 eV for polymers I and II, respectively), and narrow band gaps (1.31 and 1.41 eV, respectively). Photovoltaic devices based on a polymer-II-PC60BM (1: 3, wt/wt) mixture under AM 1.5 irradiation of 100 mV/cm2 exhibit a power-conversion efficiency of ∼0.29%, a short-circuit current of 1.45 mA/cm2, an open-circuit voltage of V oc = 0.67 V, and a fill factor of 0.30. These results are evidence that thienopyrazine functional groups are attractive as electron-acceptor building blocks in organic electronics.

В условиях реакции Стиле синтезировано четыре новых чередующихся узкозонных сополимера, содержащих бензодитиофеновые, 4,8-дитиофен-2-ил-бензо[1,2-c;4,5-c]-бис-[1,2,5]тиадиазольные, 4,9-бис-(тиофен-2-ил)-6,7-ди(2-этилгексил)-[1,2,5]тиадиазоло[3,4-g]хиноксалиновые, 5,8-дибром-2,3-бис-(5-октилтиофен-2-ил)хиноксалиновые и 4,7-бис-(5-бромтиофен-2-ил)бензо[1,2,5]тиадиазольные структуры. Строение, молекулярная масса и физические свойства сополимеров исследованы с помощью спектроскопии ЯМР 1, ГПХ, циклической вольтамперометрии, термомеханического и термогравиметрического анализов. Полимеры обладают хорошей растворимостью, широкой абсорбцией (с шириной запрещенной зоны в пределах 0.81–1.53 эВ). Все полимеры фотостабильны на воздухе, уровень высшей занятой молекулярной орбитали находится в пределах от –4.98 до –5.30 эВ. Полимерные солнечные фотоэлементы на основе этих сополимеров в качестве доноров и фуллерена РС60 в роли акцептора показывают напряжение холостого хода в интервале 0.16–0.61 В и эффективность устройств в пределах 0.02–0.49%.

Synthesis of a series of new conjugated electrochromic polymeric pyridinium salts containing main-chain triphenylamine and their electrochromic properties were demonstrated. All polymers exhibit intense UV absorptions at 336–338 nm in DMF and 340–343 nm in thin film form and fluorescence centered at 410–438 nm in DMF and 460–461 nm in thin film form. The electrochromic properties of the films were investigated by electrochemical and spectroelectrochemical methods. Reversible redox signals with stable electrochromic characteristics were obtained via cyclic voltammetry. The electrochromic properties of the polymers remain highly stable after 50 cycles between 0 and 1.2 V.

A new conjugated alternating donor-acceptor copolymer is synthesized from perylene diimide and the benzodithiophene derivative via the Suzuki reaction. Temperatures corresponding to the 10% weight loss of the copolymer in air and argon are 336 and 362°C. The copolymer is soluble in common organic solvents. The maxima of absorption spectra of the copolymer in chloroform solution and thin films are at 456 and 567 and at 444 and 567 nm, respectively. The optical band gap, as calculated from the onset of the absorption spectrum, is 1.74 eV, and the electrochemical band gap is 1.89 eV. The energies of HOMO and LUMO derived from the onset of the first oxidation and reduction potential of the cyclic voltamperogram are −5.97 and −4.08 eV. It is found that the solar cell with copolymer-to-poly(3-hexylthiophene) = 1: 1 features the best characteristics: The open circuit voltage is 0.54 V, the short circuit current is 0.976 mA/cm2, the fill factor is 0.397, and the efficiency is 0.14%. The conjugated polymer based on perylene diimide belongs to the class of n-type polymers and shows promise as an acceptor material for all-polymer bulk heterojunction solar cells.

A new conjugated alternating donor-acceptor copolymer is synthesized from perylene diimide and the benzodithiophene derivative via the Suzuki reaction. Temperatures corresponding to the 10% weight loss of the copolymer in air and argon are 336 and 362°C. The copolymer is soluble in common organic sol� vents. The maxima of absorption spectra of the copolymer in chloroform solution and thin films are at 456 and 567 and at 444 and 567 nm, respectively. The optical band gap, as calculated from the onset of the absorp� tion spectrum, is 1.74 eV, and the electrochemical band gap is 1.89 eV. The energies of HOMO and LUMO derived from the onset of the first oxidation and reduction potential of the cyclic voltamperogram are -5.97 and -4.08 eV. It is found that the solar cell with copolymertopoly(3�hexylthiophene) = 1 : 1 features the best characteristics: The open circuit voltage is 0.54 V, the short circuit current is 0.976 mA/cm 2 , the fill factor is 0.397, and the efficiency is 0.14%. The conjugated polymer based on perylene diimide belongs to the class of ntype polymers and shows promise as an acceptor mate rial for allpolymer bulk heterojunction solar cells.