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High efficiency organic solar cells (OSCs) require conjugated polymers with a low band gap, broad absorption in visible and IR region, high carrier mobility, and relatively high molecular weight as ...

A series of main chain donor-acceptor low-bandgap conjugated polymers were designed, synthesized, and used for the fabrication of polymer solar cells. The absorption spectra of low-bandgap conjugated polymers were tuned by the ratio of three copolymerization monomers. The polymers in films exhibited broad absorption ranging from 300 to 1000 nm with optical bandgaps of around 1.40 eV. All of the polymers have been investigated as an electron donor in photovoltaic cells blending with PCBM ([6, 6]-phenyl C61-butyric acid methyl ester) as an electron acceptor and power conversion efficiencies (PCEs) of 1.32–1.8% have been obtained. As for P1, PCE increases from 1.67 to 2.44% after adding 1,8-diiodooctance as an additive. The higher PCEs are probably because of better phase separation of blend films. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2571–2578, 2010

A series of polythiophene derivatives P1-P5 containing carbazole side chains were designed and synthesized via the Stille polymerization. All carbazole containing polymers showed broad absorption in the visible region. The power conversion efficiencies of solar cells based on blends of two component copolymers and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) were determinedto be0.29 and0.56% for P1and P5,respectively. For solarcells fabricated with the three component copolymers and PC61BM, the efficiencies were 0.56% for P2, 0.86% for P3, and 0.70% for P4. The introduction of electrondonating carbazole side chains can broaden the absorption in the visible region and meanwhile reduce phase separation due to the steric hinderance of the carbazole moiety to the conjugated main chain. Improving efficiency needs a balance of broad absorption and ordered packing of polymer chains in the solid state.

We present an efficient and convenient synthesis of 3,8-dibromophenanthridine derivatives and their conjugated polymers and demonstrate that phenanthridine-containing conjugated polymers can be used as luminescent chemosensor materials. High molecular weight poly(phenanthridine-co-fluorene)s (P1, P2) and poly(phenanthridine-co-p-phenylene) (P3) were synthesized by palladium-catalyzed Suzuki-Miyaura-Schluter polycondensation (SMSPC). These phenanthridine-containing polymers are of high quantum yields in solution and show reversible optical response to protonation and deprotonation of the phenanthridine rings.

Three new hydrogen bonding [60]methanofullerenes (PCB-t-BA, PCB-n-BA, and MPCB-t-BA) are synthesized, characterized, and presented for measurement of the photovoltaic properties. In comparison with the PCBM molecule, the ester group was substituted with n-butyric or t-butyric alkyl group in the two compounds. Bulk heterojunction (BHJ) organic photovoltaic devices (OPV) employing the methanofullerenes as acceptor were fabricated and optimized. An improvement of power conversion efficiencies (ηe) was observed upon application in P3HT/PCB-n-BA (ηe = 0.78%) BHJ OPV compared to P3HT/PCBM (ηe = 0.59%) without thermal annealing with the ratio of 1:1 by weight.

Star molecules have many advantages, such as monodispersity, excellent solubility, and vast structures with different functional groups. A set of four-arm star molecules with benzothiadiazole as the core, oligothiophene as the arm, and triphenylamine as the end group and their linear counterparts were designed and synthesized. Organic solar cells (OSCs) fabricated with these star molecules and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) by spin-coating from solution demonstrate similar short circuit current density (Jsc) and fill factor (FF) but larger open circuit voltage (Voc) in comparison with solar cells fabricated with corresponding linear molecules and PC71BM. A power conversion efficiency (PCE) of 1.8%, with Jsc = 4.9 mA/cm2, Voc = 0.92 V, and FF = 0.41 was achieved with one of these star molecules.

Four metal-free organic dyes (Dye-1, Dye-2, Dye-3, and Dye-4) comprising a triphenylamine moiety as the electron donor, a cyanoacrylic acid or carboxylic acid moiety as the electron acceptor and anchoring groups, and phenylethyne as the bridge were designed at the molecular level and synthesized for use in dye-sensitized solar cells (DSSCs). Their absorption spectra and electrochemical and photovoltaic properties were fully characterized, and the electron distribution with the different acceptors was calculated using density functional theory at the B3LYP/6-31G level. All of these dyes performed as sensitizers for the DSSC test, and the cyanoacrylic acid Dye-4 showed an overall conversion efficiency of 3.61% (Jsc = 9.30 mA/cm2, Voc = 0.73 V, ff = 0.49) under AM 1.5 irradiation (100 mW/cm2), which reached 79% with respect to that of an N719-based device fabricated under similar conditions. Meanwhile, the photovoltaic performance data of these phenylethyne-bridged dyes showed a higher open circuit voltage (...

We used solvent−vapor treatment methods to determine nanoscale phase separation and thus tailor the charge mobility of the poly(3-hexylthiophene)/fullerene (P3HT/C60) blend films. The nanowires obtained by chloroform vapor treatment are rich in C60, whereas the nanowires obtained by 1,2-dichlorobenzene (DCB) vapor treatment are rich in P3HT. The treated blends offer far superior hole transport than the untreated blends, which is attributed to nanoscale phase separation and a three-dimensional network containing C60 or P3HT nanowires. Meanwhile, the electrically bicontinuous nanoscale morphology realized by controlling the crystallinity of P3HT and C60 using different solvent−vapor results in enhanced absorption in visible light without further heat treatment or preparation in both cases. Solar cells fabricating from the films after treatment show several-fold improvements in power conversion efficiency compared to that of devices having films without treatment.

Three, novel dyes carrying bis-triphenylamine donor groups were designed and synthesized, and their optical and electrochemical properties were characterized. TiO(2)-based dye-sensitized solar cells fabricated with the dyes as photosensitizers displayed higher open-circuit voltage and power conversion efficiency than the corresponding mono-TPA substituted donor-acceptor dyes. The two, hydrophobic bis-triphenylamine donor groups within the dyes effectively inhibited the approach of I(3)(-) to the surface of nanocrystallite TiO(2) film. The most promising of the novel dyes displayed a power conversion efficiency of 5.06%, short circuit photocurrent density of 10.25 mA cm(-2), open circuit photovoltage of 0.678 V and fill factor of 0.73. (C) 2008 Elsevier Ltd. All rights reserved.

We report a newly synthesized polymer of a star-shaped porphyrin compound (TPA-FxP) with four oligofluorene arms at its meso positions with the pronounced enhancement of the two-photon properties and the generation of singlet oxygen by utilizing the two-photon excited fluorescence resonance energy transfer. The steady-state spectra and transient triplet-triplet absorption spectra give evidence that the enhanced two-photon absorption cross section results from not only the through-space energy transfer (Forster) but also the through-bond energy transfer between conjugated peripheral oligofluorene arms and the porphyrin core. The two-photon absorption cross section at 780 nm up to 3360 GM (1 GM = 10−50 cm4·s/photon) of TPA-FxP was obtained, which is comparable to the highest values reported from other similar chemically modified porphyrin core compounds. Furthermore, the enhanced production of singlet oxygen under two-photon absorption conditions is also reported.

Soluble conjugated alternating porphyrin−dithienothiophene copolymers—single-bond linked (I) and triple-bond linked (IIa and IIb)—were synthesized by palladium(0)-catalyzed Stille and Sonagashira coupling reactions, respectively. The thermal, electrochemical, optical, charge transport, and photovoltaic properties of these copolymers were examined; the effect of the triple bond was studied. I exhibits onset decomposition temperature (Td) of 410 °C and glass-transition temperature (Tg) of 180 °C, higher than those of IIb (Td, 330 °C; Tg, 130 °C). The absorption spectrum of I in thin film exhibits a sharp Soret band at 450 nm and two weak Q-bands at 563−619 nm, while IIb exhibits a sharp Soret band at 491 nm and a strong Q-band at 760 nm. The emission maxima of I and IIb in solution are located at 642 and 722 nm respectively. IIb is electrochemically active in both the oxidation and reduction regions, while I shows only oxidation peak. The field-effect hole mobilities as high as 2.1 × 10−4 cm2 V−1 s−1 were o...

Hyperbranched polymer-cored star polyfluorenes with high molecular weights and narrow molecular weight distribution were prepared by palladium-catalyzed one-pot Suzuki polycondensation of multi-functional cores and an AB-type monomer. The optical, electrochemical and thermal properties of the hyperbranched polymer-cored star polymers were investigated. These polymers exhibited good thermal and color stability in solid state, and there was no significant blue-green emission after the polymers had been annealed in air for 2.5 h. Their three-dimensional hyperbranched structures could effectively reduce the aggregation of the peripheral rigid linear conjugated polyfluorene chains.

Two kinds of amphiphilic dendronized conjugated polymers, polyfluorene (PF) and poly(binaphthyl-alt-fluorene) (PBF), were synthesized by Suzuki polycondensation of hydrophobic macromonomers with two nonpolar octyloxy chains and hydrophilic macromonomers with two polar oligo(ethylene oxide) chains. In these polymers, PF possesses a linear rod-like backbone structure, and PBF adopts a folded rigid backbone structure. The different configurations in the conjugated main chains result in different supramolecular self-assembly morphologies. The optical and thermal properties of PF and PBF were also studied. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 574–584, 2008

Zero-valent palladium complex, Pd(PTh3)3, with three tri(2-thienyl)phosphine ligands was prepared and characterized. Pd(PTh3)3 is superior to Pd(PPh3)4 in catalyzing Suzuki-Miyaura coupling and polymerization of thiophene-based derivatives. The Suzuki polycondensation of 3-hexyl-5-iodothiophene-2-boronic pinacol ester with Pd(PTh3)3 as the catalyst precursor afforded high-molecular-weight P3HT with high regularity and yield. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4556–4563, 2008

Porphyrin-embedded high molecular weight dendronized polymers up to fourth generation have been synthesized by Suzuki polycondensation of Frechet-type dendritic dibromo macromonomers and porphyrin diboronic pinacol ester. Higher generation lateral dendritic wedges not only endow the dendronized polymers with good solubility in commonly used organic solvents, but also prevent planar porphyrins and conjugated polymer backbones from aggregating by their “site isolation” effect. This type of porphyrin-embedded dendronized polymers can be used as saturated red light-emitting materials. With the increase of the generation of the lateral dendrons, the quantum yields of the dendronized polymers also gradually increased. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4030–4037, 2008

Conjugated polymers containing electron-transporting, hole-transporting, and blue light-emitting units were synthesized by Suzuki polycondensation. These copolymers exhibited excellent thermal and optical stability. Optical investigation indicated that the incorporation of the spirobifluorene units in the polymer main chain could markedly increase the effective conjugation length of polymers. Electrochemical studies showed that the incorporation of spirobifluorene unit could raise the electrochemical stability and improve the electron- and hole-injecting abilities. The electroluminescent results also showed that the introducing of spirobifluorene units could significantly improve the device performance. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1349–1356, 2008

The outer surface of multi-walled carbon nanotubes (MWCNTs) was successfully modified with 7-bromo-9,9-dioctylfluorene-2-carbaldehyde by using 1,3-dipolar cycloaddition of azomethine reaction to introduce bromo functional groups. The peripheral bromo functional groups can be used to further react with AB-type monomers through Suzuki polycondensation to afford the PF-functionalized MWCNTs, which are of a cable-like structure. Through covalent connection to MWCNTs, the fluorescence of polyfluorenes was completely quenched by the MWCNTs, indicating a fast photo-induced electron transfer from polyfluorenes to MWCNTs.

The green emission (g-band) in polyfluorene-based conjugated materials is studied by various spec- troscopic methods on defined poly(9,9 0 -dioctylfluorene) with one foluorenone unit (P20), which can be seen as a model compound for polyfluorene emitting g-band. The absorption and emission properties of P20 in the film and solution (room temperature) reveal the optical properties of the green emission emerging in polyfluorene-type polymer. All the experimental evidence obtained demonstrates that g-band in polyfluorene is attributed to the mono-chain fluo- renone; and the aggregation of the chains further suppresses the blue emission and enhances g-band.

To investigate the interplay between on-chain keto defect and interchain interaction and its consequence on the blue emission of polyfluorene (PF), first- to third-generation dendronized PFs as well as single-fluorenone-unit doped PF (PFN), synthesized by Suzuki polycondensation, were used as model compounds for steady-state and picosecond time-resolved photoluminescence (PL) spectroscopic studies. For PF film, the broad-band green emission did not appear, although severe interchain interaction was observed. For PFN film, the green emission that peaked at approximately 540 nm decayed in a multiphasic manner, suggesting significant heterogeneity in the excitation migration toward the keto center. To further examine the interplay effect, a series of novel dendronized-PF/PFN blend films in a molar ratio of 40:1 fluorene-to-fluorenone unit were studied. With reference to pure PFN film, those of the green emission of the blends showed strong dependence on the order of dendronization, that is, a higher generation resulted in a shorter-lived green emission. These observations are discussed in terms of interchain and/or intersegment interactions between the fluorene segments and the keto defect. It is concluded that the keto unit and the keto-centered, interchain aggregation lead to severe color degradation in a synergistic manner, and that dendronization can effectively minimize the undesirable green emission.

Monodisperse spiro-bridged ladder-type oligo-p-phenylenes, which have very rigid backbones, exhibited intensive emissions with very small Stocks shifts, displayed very good color stability upon thermo-oxidation, and were synthesized by Suzuki cross-coupling, oxidation, and BF3.ether-catalyzed cyclization reactions.

A set of water-soluble dendronized polyfluorenes bearing peripheral charged amino groups were synthesized by two steps: (1) Suzuki polycondensation of dendritic macromonomers carrying peripheral B...

A functional coil-rod-coil triblock copolymer containing a terfluorene unit as the rigid segment and poly(N-isopropylacrylamide) (PNIPAAm) as the flexible block was successfully synthesized via reversible addition-fragmentation chain-transfer (RAFT) polymerization using terfluorene-based dithioester as the RAFT agent. The temperature-responsive optical properties were investigated with the aid of dynamic light scattering and fluorescence techniques. Additionally, the relationship between the optical properties and the reversible phase transition of the doping system formed by blending the copolymer with tetraphenylporphine tetrasulfonic acid was studied. Above the lower critical solution temperature, the energy transfer efficiency decreased as a result of the globule-to-coil transition from PNIPAAm segments. The result indicates that these copolymers have a potential to be used as responsive fluorescent probes in facile detection of dye-labeled biopolymers.

1c. A mixture of 1b (336 mg, 0.6 mmol), CuI (2 mg, 0.012 mmol), Pd(PPh3)2Cl2 (4 mg, 0.006 mmol) and trimethylamine (10 mL) in a Schlenk tube was carefully degassed and charged with nitrogen. Trimethylsilylacetylene (100 µL, 0.7 mmol) was injected and the tube was sealed at once. The reaction mixture was stirred at room temperature for 24 h. After the removal of the solvent, the residue was purified by chromatography on silica gel eluting with petrol ether to afford 1c as a colorless oil (262 mg, 82%). 1 H NMR (400 MHz, CDCl3): δ 7.73 (1H, d), 7.67-7.63 (3H, m), 7.57 (1H, d), 7.53 (1H, s), 7.47-7.44 (4H, m), 7.36 (1H, t), 1.99-1.97 (4H, m), 1.20-1.04 (20H, m), 0.81 (6H, t), 0.62-0.61 (4H, m), 0.29 (9H, s). 13 C NMR (100 MHz, CDCl3): δ 152.4, 151.5, 142.2, 142.0, 141.2, 140.3, 131.9, 129.4, 127.9, 126.9, 126.8, 122.2, 121.9, 120.9, 120.2, 107.0, 94.6, 55.9, 41.0, 32.4, 30.6, 29.9, 24.3, 23.2, 14.7, 0.74. Anal. Calcd for C40H54Si: C, 85.34; H, 9.67. Found: C, 84.20; H, 9.56. 1d. 1c (202 mg, 0.36 mmol) was dissolved in dry dichloromethane. Then tetrabutylammonium fluoride (1 M in THF, 540 µL, 0.54 mmol) was added. The mixture was stirred at room temperature for 10 min. The reaction mixture was poured onto a short pad of silica gel. Chromatography eluting with dichloromethane afforded 1d as a colorless oil in a yield of 98%. 1 H NMR (400 MHz, CDCl3): δ 7.74 (1H, d), 7.66 (3H, d), 7.58 (1H, d), 7.54 (1H, s), 7.50-7.45 (4H, m), 7.37 (1H, t), 3.15 (1H, s), 2.00-1.96 (4H, m), 1.20-1.05 (20H, m), 0.81 (6H, t), 0.64 (4H, m). 13 C NMR (100 MHz, CDCl3): δ 152.4, 151.6, 142.2, 141.4, 140.2, 131.9, 129.5, 127.9, 127.2, 126.8, 122.2, 121.0, 120.8, 120.3, 85.4, 55.9, 41.0, 32.4, 30.6, 29.9, 24.4, 23.3, 14.7. Anal. Calcd for C37H46: C, 90.55; H, 9.45. Found: C, 90.40; H, 9.56. A1. A mixture of 1b (290 mg, 0.49 mmol), 1d (200 mg, 0.4 mmol), CuI (2 mg, 0.008 mmol), Pd(PPh3)2Cl2 (3 mg, 0.004 mmol), THF (6 mL) and diisopropylamine (4 mL) in a Schlenk tube was carefully degassed and charged with nitrogen. The tube was sealed and the reaction mixture was stirred at

The growth behavior of the rod-like α-form crystals from both the liquid crystal and the isotropic melt state was studied in situ and in real time using a hot-stage atomic force microscopy. The growth rate and direction of the poly(9,9-dioctylfluorene) (PFO) α-form crystals are greatly affected by the orientation of the polymer chains in the liquid crystal matrix. The pre-existence of chain alignment in the liquid crystal matrix serves as a precursor for crystallization, which greatly reduces the growth energy barrier and promotes the overall growth rate of PFO α-form crystals. Our results provide some valuable information for understanding the relationship between morphology and photoexcited emission behaviors.

The morphology and photoelectronic properties of blend films of poly(9,9′-dioctylfluorine) (PF) and ethyl–cyanoethyl cellulose [(E-CE)C] were investigated. It was found that the morphology of the blends was changed with the blend composition. The lateral phase separation was observed in submicron scale, and a nanoscale vertical phase separation occurred with enrichment of the (E-CE)C at the surface of the blend films. The photoluminescent spectra of the blend films are blue-shifted with the increase of the (E-CE)C. The photoelectronic properties of the blends varied with the morphology of the blends. In the electroluminescent device, the turn-on voltage was almost identical for the device with 50% or above 50 wt % PF in blend films and markedly improved for the device with only 25 wt % PF. The external quantum efficiency of the device fabricated with 75% PF is the highest among the device fabricated with the PF/(E-CE)C blend films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

A series of conjugated triblock copolymers containing hole-transporting polycarbazole segments, electron-transporting polyoxadiazole segments, and blue-light-emitting polyfluorene segments were prepared with a two-step palladium-catalyzed Suzuki polycondensation (SPC). First dibromo-terminated polymer precursors (polyfluorenes and polyoxadiazoles) were synthesized as the central buildingblocks. Then, the dibromo-terminated polymer precursors were further polymerized with AB-type monomers [2-bromo-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9-octylcarbazole, 3-bromo-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9-octylcarbazole, and 2-bromo-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-dioctylfluorene] to achieve the target triblock copolymers under SPC conditions. The formation of the triblock copolymers was confirmed by gel permeation chromatography and NMR spectroscopy. The triblock copolymers exhibited good thermal stability. An investigation of the photophysical properties indicated that efficient, photoinduced through-bond energy transfer occurred in such triblock copolymer systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2410–2424, 2007

C60-cored star polyfluorenes were synthesized and fully characterized. A high yield (81%) hexakisaddition of C60 was developed by using Prato reaction and bulky fluorene addends. Suzuki polycondensation of the hexakisadducts of C60 carrying six 2-bromofluorene addends and AB-type monomer (2-bromo-9,9-dioctylfluorenyl-4,4,5,5-tetramethyl- [1,3,2]-dioxaborane) with Pd(PPh 3 ) 4 as the catalyst precursor afforded the desired C60-cored star polyfluorenes. Their three-dimensional structure can effectively reduce the aggregation of the polyfluorene chains. Annealing studies indicated that the C60-cored star polyfluorenes are of good color stability.

A set of AB2 type monodisperse conjugated oligomers carrying two bromo functional groups and one boronic ester functional group were prepared by iterative deprotection and Sonogashira cross-coupling reactions. Suzuki polycondensation of these AB2 type monodisperse oligomers afforded hyperbranched polymers. The hyperbranched conjugated polymers we prepared possess not only precisely controlled conjugation length like monodisperse conjugated oligomers but also the structural feature of hyperbranched polymers. Optical property investigation demonstrated that the maximum absorption and emission wavelength red-shifted along with the increasing of the conjugation length between the two branching points and the hyperbranched structure could effectively reduce the aggregation of the conjugated polymer chains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1084–1092, 2007

A new 1,8-naphthalimide based planar small molecular acceptor and two benzothiadiazole based wide band gap (WBG) polymer donors P1 and P2 were synthesized for nonfullerene organic photovoltaic cells (OPVs). Devices based on fluorinated polymer P2 achieved a highly improved PCE of 3.71% with an open circuit voltage (V(oc)) of 1.07 V, which is beyond the currently known levels for nonfullerene OPVs with the V(oc) higher than 1 V.

The use of a commercially available nucleating agent as the additive for the fabrication of polymer:PC71BM-based active layers by solution-processing can greatly enhance the power conversion efficiency (PCE) of bulk heterojunction polymer solar cells (BHJ PSCs). The enhancement of device performance is mainly due to the addition of nucleating agent, which is able to regulate the drying process of the active layer and decrease the oversized domain size of conjugated polymers. Via this effective strategy to optimize the film morphology, the designed device exhibits an enhancement as great as 30.8%.

Solution processable star-shaped donor–acceptor (D–A) conjugated molecules (TPA-T-NI and TPA-3T-NI) with an electron-donating triphenylamine (TPA) core, three thienylene or terthienylene spacers, and three 1.8-naphthalimide (NI) electron-withdrawing end-groups are explored for the first time as charge storage materials for resistor-type memory devices owing to the efficient electric charge transfer and trapping.

An anthracene derivative, 2,6-diphenyl anthracene (DPA), was successfully synthesized with three simple steps and a high yield. The compound was determined to be a durable high performing semiconductor with thin film device mobility over 10 cm(2) V(-1) s(-1). The efficient synthesis and high performance indicates its great potential in organic electronics.

Three conjugated polymers (P1-P3) with benzodithiophene derivatives as the donor unit, 5-fluoro-6-(2-hexyldecyloxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5] thiadiazole as the acceptor unit and thiophene as the spacer were designed, synthesized, and used as donor materials for polymer solar cells (PSCs). The influence of side chains at the benzodithiophene unit on the performance of PSCs was investigated. PSCs with the blend of P2:PC71BM (1:2, by weight) as the active layer show the highest power conversion efficiency (PCE) of 6.88%, with an open circuit voltage (Voc) of 0.76 V, a short circuit current (Jsc) of 14.67 mA/cm(2), and a fill factor (FF) of 0.62. Our research revealed that the variation of side chains had a great influence on the morphology of blend films, which is crucial to the performance of PSCs. As indicated by transmission electron microscopy, the blends of P1:PC71BM (1:2) and P2:PC71BM (1:2) formed nanofibers, whereas the blends of P3:PC71BM (1:2) formed spherical domains. Therefore, we concluded that formation of a more interpenetrating phase-separated donor-acceptor network with a larger interfacial area and proper percolation in the blends from P1 to P2 is mainly responsible for better performance in the corresponding devices.

Performance enhancement of polymer solar cells (PSCs) is achieved by expanding the absorption of the active layer of devices. To better match the spectrum of solar radiation, two polymers with different band gaps are used as the donor material to fabricate ternary polymer cells. Ternary blend PSCs exhibit an enhanced short-circuit current density and open-circuit voltage in comparison with the corresponding HD-PDFC-DTBT (HD)- and DT-PDPPTPT (DPP)-based binary polymer solar cells, respectively. Ternary PSCs show a power conversion efficiency (PCE) of 6.71%, surpassing the corresponding binary PSCs. This work demonstrates that the fabrication of ternary PSCs by using two polymers with complementary absorption is an effective way to improve the device performance.

Organic semiconducting materials have been become the cornerstone of organic electronics, including photovoltaic cells, light-emitting diodes, field effect transistors, and electrochromic devices. The synthesis of new organic semiconducting materials and the development of new synthetic methods for preparing semiconducting organic materials are two important issues which are currently attracting great attention. This chapter mainly focuses on the new developments in the synthesis of conjugated polymers used for organic photovoltaics.

A novel kind of dendronized porphyrin polymers was synthesized by Sonogashira coupling of diethynyl-functionalized porphyrin monomers and diiodo-functionalized macromonomers bearing Frechet-type dendrons. The encapsulation of red-light-emitting porphyrin-containin g conjugated backbones into dendronized polymers can not only reduce the aggregation of polymer backbones and the self-quenching of their fluorescence but also endow the porphyrin polymers with good solubility. We also report the optical and electrochemical properties of the porphyrin-containing dendronized polymers.

Porphyrin-containing conjugated polymers with fluorene or carbazole as spacer groups were prepared by Sonogashira cross-coupling reactions. The polymers were of high molecular weight and the flexible alkyl chains on fluorene or carbazole units made the conjugated polymers soluble in common organic solvents, such as THF and methylene chloride. The polymers could form high quality durable films from solution casting. Their optical and photocurrent responsive properties were investigated. It was found that the photocurrent response was directly proportional to the content of porphyrin. The incorporation of carbazole units into the polymer chains also gave positive contribution to the photocurrent generation in some extent.

Summary: Properties of a series of hyperbranched polyfluorenes were investigated. Increasing the benzene “crosspoint” density blue-shifts the absorption and PL since the crosspoints interrupt π-electron conjugation, decreasing conjugation length, and thus increasing chromophore band gap. The relative intensity of S10 → S00 transition in PL increases with crosspoint density increase, indicating that the energy and the energy distribution of vibronic transitions were controlled by hyperbranch structure. When the polymer solution is cooled down, the lattice vibration is reduced and the effective conjugation length (coherence length for electron wavefunction) is increased, thus causing bathochromic shift in absorption and PL. These polymers do not favor excimer formation in solution due to their remarkable rigidity and extra-large molecular size. With increase in crosspoint density, LED color changed from green to violet. In double-layer LEDs, PPV not only improves hole injection/transport but also contributes to device emission through its bulk emission and interfacial emission as a result of interfacial energy transfer. Higher electrical field favors interfacial energy transfer probably by facilitating hole–electron recombination and by encouraging the excitons formed in polyfluorene layer to migrate to the interface and to further diffuse into PPV layer. The polymer with more crosspoints shows higher EL efficiency. The crosspoints interrupt π-electron conjugation, isolate excitons and inhibit intrachain exciton annihilation. They can also increase rigidity of the macromolecular backbone, and the large spatial hindrance of these macromolecules makes the molecular packing very difficult, thus decreasing interchain exciton annihilation. All these structural features help to increase exciton lifetime and improve LED performance. Synthesis of the hyperbranched polyfluorenes.

Dye-capped, hyperbranched, conjugated polymers were prepared by the modification of the peripheral bromo end groups of the hyperbranched polymer core with a palladium-catalyzed Suzuki–Miyaura cross-coupling reaction. The dye-modified, hyperbranched polymers had high molecular weights and displayed good solubility in common organic solvents such as tetrahydrofuran, toluene, and chloroform. The structure of the dye-modified, hyperbranched polymers was characterized by 1H and 13C NMR and elemental analysis. The thermal properties of five kinds of hyperbranched polymers were investigated with thermogravimetric analysis and differential scanning calorimetry. The optical properties of the dye-capped, hyperbranched polymers were investigated with ultraviolet-absorption and fluorescence spectroscopy. The hyperbranched structure could effectively reduce the aggregation of the peripheral dyes. The emission colors of the hyperbranched polymers could be easily tuned by end-group modification. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 111–124, 2007

A set of monodisperse oligo(9,9-dioctylfuorene)s, each containing only one fluorenone unit, was synthesized by using iterative Suzuki cross-coupling and iododesilylation reactions. Their optical properties were also investigated.

A kind of novel dibromocarbazole monomer bearing three alkyl chains was prepared. Two strategies were developed to improve the solubility and molecular weight of carbazole polymers. One was the polymerization of N-octyl-2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)carbazole with the alkylated dibromocarbazole. Another one was the polymerization of N-octyl-2,7-bis(4,4,5,5-tetramethyl-l,3,2-dioxaborolan-2-yl)carbazole with N-octyl-3,6-dibromocarbazole. All the polymerizations were carried out under palladium-catalyzed Suzuki polycondensation (SPC) conditions. Through using carbazole monomer bearing three alkyl chains to polymerize, we have successfully boosted the number-average molecular weight of 2,7-linked carbazole polymers from not more than 5 to 67 kDa. The high-molecular-weight polymers were obtained in high yields and displayed good solubility in common organic solvents. Their optical, electrochemical, and thermal properties were also reported.

Conjugated three- and four-arm star polymers were successfully prepared by palladium catalyzed one-pot Suzuki polycondensation of the multifunctional cores and an AB-type monomer. The molecular weight of the star polymers could be controlled by the feed ratios of the monomers. The bromo end groups could be completely modified by fluorene mono boronic acid or triphenylamine mono boronic ester. The investigation of the optical, electrochemical, and thermal properties of the star polymers was also reported. All polymers exhibited good thermal stabilities and all the TPA-capped polymers showed good hole-transport abilities.

Monodisperse asymmetrical oligo(phenylene‐ethynylene)s were synthesized iteratively by combining the selective deprotection and the Sonogashira coupling. Trimethylsilylethyl ester (TSE) and trimethylsilyl (TMS) were used as protecting groups for carboxyl and acetylene, respectively. The acetylenic TMS protecting group could be removed selectively by the treatment with TBAF in methylene chloride, whereas both TSE and TMS protecting groups were cleaved in THF.

Two kinds of triphenylamine-containing AB2 monomers carrying or not carrying flexible alkyl chains were synthesized and fully characterized. One-pot Suzuki polycondensation (SPC) was applied to polymerize these monomers to prepare hyperbranched polymers. Hyperbranched polymers from AB2 monomer not carrying alkyl chains exhibited poor solubility in common organic solvents such as THF, chloroform, toluene, etc. The poor solubility of the hyperbranched polymers hampered their applications and the further modification of the end groups. The introduction of difunctional core molecules, such as 9,9-dioctylfluorene and 9,9-dioctylfluorene trimer, in the polymerization process controlled the molecular weight and forced the hyperbranched copolymers soluble in common organic solvents mentioned above, but high molecular weight polymers could not be obtained. SPC of the AB2 monomers carrying flexible alkyl chains afforded high molecular weight fluorene−triphenylamine (F−TPA) alternating hyperbranched copolymers, whic...

Single-chain manipulation of two second-generation dendronized polymers, hydrophobic and amphiphilic poly(p-phenylene), was performed by using single-molecule force spectroscopy on the basis of atomic force microscopy. In tetrahydrofuran (THF) buffer, the individual amphiphilic dendronized polymer chain exhibits larger elasticity than the corresponding hydrophobic dendronized polymer chain does. The larger elasticity of the single amphiphilic polymer chain is probably from the collapse of oligoethyleneoxy chains in THF, which is a poor solvent for them. While using CH 2 Cl 2 as a buffer, all the side groups can be expanded; the elasticity of the amphiphilic polymer chain is therefore smaller than that in THF. The individual hydrophobic polymer exhibits the same elasticity in THF and CH 2 Cl 2 because of the similar polymer chain conformation in the two buffers. Moreover, the adhesion-force measurements in a poor solvent at the interface reveal that the poor solubility of the polymer side groups as well as the hydrophobic interaction between the surface and the polymer side groups enhances the adhesion force.