Study On Synthesis And Photoelectric Properties Of Polyfluorene Copolymers Containing Polyether Side Chains

Conjugated polymers are a class of organic semiconductor. Because of itsflexibility and optical properties, thermal stability, good environmental, they arewidely used in organic optoelectronic devices，such as light emitting diodes，solarcells and field effect transistors.Due to the efficient and pure blue electroluminescence polyfluorene-basedconjugated polymers become an important class of organic conjugated semiconductormaterials, especially in display applications. Furthermore, polyfluorene-basedconjugated polymers have very high photoluminescence quantum yield, ease ofstructural modification，and easy to deal with by spin coating method. Therefore, theyhave attracted lots of material chemists’ attention. The UV-vis absorption ofpolyfluorenes is in the blue range, so polyfluorenes are not suitable for a solar celldevice as the active layer. But through structural modification they can be applied inthe solar cell devices. Usually, we can introduce a donor acceptor narrow band gapsegment in the polymer main chain to improve its spectral absorption range and bandgap. In addition, we can introduce the modifying group in the side chain to obtainpolymers with specific properties, and they can be applied to solar cell device asmodified electrode layer.In this thesis, we synthesized a series of polyfluorene copolymers containingpolyether side chains and studied its optical properties. In chapter II, poly{[2,7-(9,9-bis-(1-(2-(2-methoxyethoxy)ethoxy)ethyl)-fluorene)]-alt-[5,5-(4,7-di-2’-thienyl-2,1,3-benzothiadiazole)]}(EO-PF-DTBT) was synthesized via a Suzukicoupling reaction of monomer2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-di(1-(2-(2-methoxyethoxy)ethoxy)ethyl)fluorine (4) and4,7-bis(2-bromo-5-thienyl)-2,1,3-benzothiadiazole (DTBT)(1:1). The solar cells devicesbased on EO-PF-DTBT and PC61BM were fabricated with device structureITO/PEDOT:PSS/EO-PF-DTBT:PC61BM(1:2)/Ca/Al. Solar cells devices show maximum power conwerion efficience (PCE) of2.65%with an open circuit voltage(VOC) of0.86V, a short circuit current density (JSC) of6.10mA/cm2, and a fill factor(FF) of51%under AM1.5G illumination at100mW/cm2, which is treated with1,8-diiodooctane (DIO). DIO treatment significantly improved excessive aggregationof EO-PF-DTBT molecules, and improved the energy conversion efficiency of thedevice.In chapter Ш, five polymers (P1、P2、P3、P4、P5) were synthesized via Suzukicoupling reaction of monomer2,7-dibromo-9,9-di(2-(2-(2-methoxyethoxy)ethoxy)ethyl)fluorine and2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-dioctylfluorene which act as blue chromophore, different proportions of4,7-di(2-dibromo-5-thienyl)-2,1,3-benzothiadiazole (DTBT) which act as redchromophore and4,7-dibromo-2,1,3-benzothiadiazole (BT) which act as greenchromophore. Hope to give a white electrochemical cell copolymer by adjusting theratio of red and green chromophore, in order to realize white light emitting of acopolymer. This can avoid phase separation and other negative factors caused byphysical mixing of several materials.In chapter Ⅳ， novel copolymers Poly{[2,7-(9,9-bis-(1-(2-(2-methoxyethoxy)ethoxy)ethyl)-fluorene)]-alt-[2,7-dibromo-9,9-di(2-hydroxyethyl)fluorine]}(P6)，Poly{[2,7-(9,9-bis-(1-(2-(2-methoxyethoxy)ethoxy)ethyl)-fluorene)]-alt-[2,7-dibromo-9,9-di(2,3-propanediol-1-yl)fluorine]}(P7), Poly{(9,9-bis(3’-(N,N-dimethylamino) propyl)-2,7-fluorene)-alt-[2,7-(9,9-bis-(1-(2-(2-methoxyethoxy)ethoxy)ethyl)-fluorene)](P8)were synthesized by the palladium-catalyzed Suzuki coupling reaction. Polymer P8quaternized ammonium polyelectrolyte derivatives (P9) was obtained through apostpolymerization treatment on the terminal amino groups. Then the polymers werecharacterized by UV-vis, fluorescence, infrared and other tests. Study found that,polymers P6and P7can be dissolved in a polar solvent, such as DMSO and DMF,and polymer P9can be dissolved in methanol and a mixed solution of methanol andwater. Because of their specific solubility and functional groups they can be used asthe modification layer of the organic photovoltaic devices.