Synthesis and characterization of indeno[1,2-b]fluorene-based low bandgap copolymers for photovoltaic cells

Kim, Jinseck,Kim, Sun Hee,Jung, In Hwan,Jeong, Eunjae,Xia, Yangjun,Cho, Shinuk,Hwang, In-Wook,Lee, Kwanghee,Suh, Hongsuk,Shim, Hong-Ku,Woo, Han Young Royal Society of Chemistry 2010 Journal of materials chemistry Vol.20 No.8

<P>Two types of indenofluorene-based low bandgap conjugated polymers, poly(6,6′,12,12′-tetraoctylindeno[1,2-b]fluorene-co-4,7-bis(2-thienyl)-2,1,3-benzothiadiazole) (<B>PIF-DBT</B>) and poly(6,6′,12,12′-tetraoctylindeno[1,2-b]fluorene-co-5,7-dithien-2-yl-thieno[3,4-b]pyrazine) (<B>PIF-DTP</B>), were synthesized and characterized for use in plastic solar cells. The optical, electrochemical, charge carrier mobility, morphological and photovoltaic characteristics were investigated. The number-average molecular weights of the polymers measured by gel permeation chromatography ranged from 19 000 to 27 000 g mol<SUP>−1</SUP>. The polymers were fairly soluble in common organic solvents and formed optical-quality films by spin casting. Photophysical studies revealed a low bandgap of ∼1.9 eV for <B>PIF-DBT</B> and ∼1.6 eV for <B>PIF-DTP</B>, respectively, which could harvest the broad solar spectrum covering from 300 nm to 650 nm (<B>PIF-DBT</B>), and from 300 nm to 800 nm (<B>PIF-DTP</B>) in film. An electrochemical study confirmed the desirable HOMO/LUMO levels of the copolymers, which enable efficient electron transfer and a high open circuit voltage when blending them with fullerene derivatives. The field effect mobility measurements showed a hole mobility of 10<SUP>−5</SUP>∼10<SUP>−3</SUP> cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP> for the copolymers. The film surface morphology was also studied by atomic force microscopy. Among the polyindenofluorene copolymers, <B>PIF-DBT50</B> (containing 50 mol% DBT) showed the best photovoltaic performance with an open circuit voltage of 0.77 V, a short circuit current of 5.50 mA cm<SUP>−2</SUP> and a power conversion efficiency of 1.70% when the polymers were blended with PC<SUB>71</SUB>BM, under air mass 1.5 global (AM 1.5G, 100 mW cm<SUP>−2</SUP>) illumination conditions.</P> <P>Graphic Abstract</P><P>The indenofluorene-based copolymers were synthesized and their photovoltaic properties were investigated. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b919033c'> </P>

Synthesis and characterization of indeno[1,2-b]fluorene-based white light-emitting copolymer

Jeong, Eunjae,Kim, Sun Hee,Jung, In Hwan,Xia, Yangjun,Lee, Kwanghee,Suh, Hongsuk,Shim, Hong-Ku,Woo, Han Young Wiley Subscription Services, Inc., A Wiley Company 2009 Journal of polymer science Part A, Polymer chemist Vol.47 No.14

<P>An indenofluorene-based copolymer containing blue-, green-, and red light-emitting moieties was synthesized by Suzuki polymerization and examined for application in white organic light-emitting diodes (WOLEDs). Tetraoctylindenofluorene (IF), 2,1,3-benzothiadiazole (BT), and 4,7-bis(2-thienyl)-2,1,3-benzothiadiazole (DBT) derivatives were used as the blue-, green-, and red-light emitting structures, respectively. The number-average molecular weight of the polymer was determined to be 25,900 g/mol with a polydispersity index of 2.02. The polymer was thermally stable (T<SUB>d</SUB> = ∼398 °C) and quite soluble in common organic solvents, forming an optical-quality film by spin casting. The EL characteristics were fine-tuned from the single copolymer through incomplete fluorescence energy transfer by adjusting the composition of the red/green/blue units in the copolymer. The EL device using the indenofluorene-based copolymer containing 0.01 mol % BT and 0.02 mol % DBT units (PIF-BT01-DBT02) showed a maximum brightness of 4088 cd/m<SUP>2</SUP> at 8 V and a maximum current efficiency of 0.36 cd/A with Commission Internationale de L'Eclairage (CIE) coordinates of (0.34, 0.32). The EL emission of PIF-BT01-DBT02 was stable with respect to changes in voltage. The color emitted was dependent on the thickness of the active polymer layer; layer (∼60 nm) too thin was unsuitable for realizing WOLED via energy transfer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3467–3479, 2009</P> <B>Graphic Abstract</B> <P>We have synthesized an indenofluorene-based copolymer composed of blue-, green-, and red-emitting comonomers by Suzuki polymerization to produce white-light emission. By fine-tuning the composition of red/green/blue units and partial energy transfer among them, pure and stable white emission was obtained with the polymer containing 0.01 mol % 2,1,3-benzothiadiazole and 0.02 mol % 4,7-bis(2-thienyl)-2,1,3-benzothiadiazole. It showed bright white electroluminescence (4088 cd/m<SUP>2</SUP>) and a luminance efficiency of 0.36 cd/A with the CIE coordinates of (0.34, 0.32). The color emitted was dependent on the thickness of the active layer; a layer too thin was unsuitable for realizing white emission via energy transfer. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]</P> <img src='wiley_img/0887624X-2009-47-14-POLA23422-gra001.gif' alt='wiley_img/0887624X-2009-47-14-POLA23422-gra001'>

Synthesis and Photovoltaic Properties of Alternating Conjugated Polymers Derived from Thiophene-Benzothiadiazole Block and Fluorene/Indenofluorene Units

Jianfeng Li,Junfeng Tong,Peng Zhang,Chunyan Yang,Dejia Chen,Yuancheng Zhu,Yangjun Xia,Duowang Fan 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.2

A new donor-accepter-donor-accepter-donor (D-A-D-A-D) type 2,1,3-benzothiadiazole-thiophene-based acceptor unit 2,5-di(4-(5-bromo-4-octylthiophen-2-yl)-2,1,3-benzothiadiazol-7-yl)thiophene (DTBTTBr2) was synthesized. Copolymerized with fluorene and indeno[1,2-b]fluorene electron-rich moieties, two alternating narrow band gap (NBG) copolymers PF-DTBTT and PIF-DTBTT were prepared. And two copolymers exhibit broad and strong absorption in the range of 300-700 nm with optical band gap of about 1.75 eV. The highest occupied molecular orbital (HOMO) energy levels vary between –5.43 and –5.52 eV and the lowest unoccupied molecular orbital (LUMO) energy levels range from –3.64 to –3.77 eV. Potential applications of the copolymers as electron donor material and PC71BM ([6,6]-phenyl-C71 butyric acid methyl ester) as electron acceptors were investigated for photovoltaic solar cells (PSCs). Photovoltaic performances based on the blend of PF-DTBTT/PC71BM (w:w; 1:2) and PIF-DTBTT/PC71BM (w:w; 1:2) with devices configuration as ITO/ PEDOT: PSS/blend/Ca/Al, show an incident photon-to-current conversion efficiency (IPCE) of 2.34% and 2.56% with the open circuit voltage (Voc) of 0.87 V and 0.90 V, short circuit current density (Jsc) of 6.02 mA/ cm2 and 6.12 mA/cm2 under an AM1.5 simulator (100 mW/cm2). The photocurrent responses exhibit the onset wavelength extending up to 720 nm. These results indicate that the resulted narrow band gap copolymers are viable electron donor materials for polymer solar cells.

A New Anthracene-based Small Molecule as Cathode Interlayer for Efficient Polymer Solar Cells

Jianfeng Li,Chuang Zhao,Peng Zhang,Junfeng Tong,Chunyan Yang,Yangjun Xia,Duowang Fan 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.4

A new small molecule with excellent electron-transporting property, namely 9,10-bis(2-(N-octyl-1,8-naphthalimid-4-yl)ethynyl)anthracene (BNA), is prepared and characterized. A polymer solar cell (PSC) based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenylC61-butyricacidmethyl ester (PC61BM) is also fabricated by using BNA as the cathode buffer layer between the Al electrode and photoactive layer, and their influence on the performance of the PSCs is investigated. It is found that the open-circuit voltage (V oc ), short-circuit current density (J sc ), and power conversion efficiency (PCE) of a device with a 6-nm BNA layer improved to 0.63 V, 9.74 mA/cm2, and 3.74%, respectively, which correspond to an increase of 53.6%, 38.0%, and 177% compared to those without the buffer layer. The BNA buffer layer could effectively improve the interfacial contact performance between the Al electrode and photoactive layer, decrease the series resistance, and improve the collection efficiency of carriers. The devices with appropriate thickness of the BNA buffer layer can also replace the common low-work-function metal Ca for increasing the PCE and lifetime of PSCs.

Synthesis and Photovoltaic Properties of Alternating Conjugated Polymers Derived from Thiophene-Benzothiadiazole Block and Fluorene/Indenofluorene Units

Li, Jianfeng,Tong, Junfeng,Zhang, Peng,Yang, Chunyan,Chen, Dejia,Zhu, Yuancheng,Xia, Yangjun,Fan, Duowang Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.2

A new donor-accepter-donor-accepter-donor (D-A-D-A-D) type 2,1,3-benzothiadiazole-thiophene-based acceptor unit 2,5-di(4-(5-bromo-4-octylthiophen-2-yl)-2,1,3-benzothiadiazol-7-yl)thiophene ($DTBTTBr_2$) was synthesized. Copolymerized with fluorene and indeno[1,2-b]fluorene electron-rich moieties, two alternating narrow band gap (NBG) copolymers PF-DTBTT and PIF-DTBTT were prepared. And two copolymers exhibit broad and strong absorption in the range of 300-700 nm with optical band gap of about 1.75 eV. The highest occupied molecular orbital (HOMO) energy levels vary between -5.43 and -5.52 eV and the lowest unoccupied molecular orbital (LUMO) energy levels range from -3.64 to -3.77 eV. Potential applications of the copolymers as electron donor material and $PC_{71}BM$ ([6,6]-phenyl-$C_{71}$ butyric acid methyl ester) as electron acceptors were investigated for photovoltaic solar cells (PSCs). Photovoltaic performances based on the blend of PF-DTBTT/$PC_{71}BM$ (w:w; 1:2) and PIF-DTBTT/$PC_{71}BM$ (w:w; 1:2) with devices configuration as ITO/PEDOT: PSS/blend/Ca/Al, show an incident photon-to-current conversion efficiency (IPCE) of 2.34% and 2.56% with the open circuit voltage ($V_{oc}$) of 0.87 V and 0.90 V, short circuit current density ($J_{sc}$) of $6.02mA/cm^2$ and $6.12mA/cm^2$ under an AM1.5 simulator ($100mA/cm^2$). The photocurrent responses exhibit the onset wavelength extending up to 720 nm. These results indicate that the resulted narrow band gap copolymers are viable electron donor materials for polymer solar cells.