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On–off-switchable, persistent, room-temperature phosphorescence (373 ms) is realized in organic solids based on bis(4-(9H-carbazol-9-yl)phenyl)methanone. The reversible on–off RTP switching can be controlled by repeatedly chloroform fuming and heating (or grinding). Multi­ple-color fluorescence is also feasible, and they reversibly convert to each other under the stimuli of heating, shearing, and fuming with varied solvents.

A series of novel star-shaped small molecules with triphenylamine as the core, oligothiophene as the spacer and 1,8-naphthalimide as the electron withdrawing end-group were synthesized and used as donor materials for solution-processed organic solar cells. Direct arylation and Suzuki cross-coupling were used to synthesize the key intermediates and star-shaped molecules. The star-shaped molecules showed good thermal stability, intense absorption in the range of 300–700 nm, and deep HOMO energy level. A bulk heterojunction organic solar cell with one of the star shaped molecules in combination with PC71BM as the active layer gave a power conversion efficiency of 2.32% with a high open-circuit voltage up to 0.94 V. The influence of the spacer between the triphenylamine core and the peripheral 1,8-naphthalimide function group on the optical and photovoltaic properties was also investigated. Our studies indicated that 1,8-naphthalimide can be used as a promising building block for the synthesis of novel donor materials for organic solar cells.

Two conjugated polymers HXS-1 and PDFCDTBT were prepared by direct C-H activation and Suzuki polycondensation and their chemical structures were characterized by 1H NMR spectroscopy. The molecular weight of conjugated polymer synthesized by direct C-H activation is lower than the corresponding polymers prepared by Suzuki polycondensation. Conjugated polymers synthesized by direct C-H activation have considerable solubility in common organic solvents and form amorphous film. The photovoltaic property of conjugated polymers synthesized by direct C-H activation is inferior to the corresponding polymers synthesized by Suzuki polycondensation.

Four planar conjugated polymers called CZ-BO8, CZ-BO12, CZ-BT8 and CZ-BT12 with carbazole as the donor unit and benzooxadiazole or benzothiadiazole as the acceptor unit have been synthesized and characterized. These four polymers have medium band gaps (1.95-1.97 eV), low lying highest occupied molecular orbital energy levels (below -5.5 eV), relatively high hole mobilities (in the range of 0.026-0.1 cm(2) V-1 s(-1)), and on/off current ratio of 10(6) without any post-treatment. Furthermore, high performance thin film phototransistors based on these four polymers have also been fabricated with high photocurrent/dark current ratios (5.7 x 10(3)-8.2 x 10(3)). Interestingly, phototransistors based on CZ-BO8 and CZ-BO12 show a faster photoresponse than that based on CZ-BT8 and CZ-BT12, providing valuable molecular design guidelines for high performance photoresponse polymers.

We investigated photovoltaic performances of polymer solar cells depending on three materials (P1/PC71BM, P2/PC71BM, P3/PC71BM) that embedded with a certain sized (35 nm) Ag nanoparticles (NPs) between indium tin oxide (ITO) and PEDOT : PSS anode buffer layer. The power conversion efficiency of the three solar cells enhanced by 13.6%, 21.1%, and 16.0%, respectively, and the increase mainly originated from Jsc. The other measurements and investigations demonstrated that both the optical and electrical properties made contributions to the development of device performances. The introduction of Ag NPs between ITO substrates and PEDOT : PSS layers is one of the most effective approaches to improve the polymer solar cell performance.

A novel small molecule NI-T-NI with a thiophene core and two 1,8-naphthalimide terminal groups was synthesized via direct C–H activation and used as the acceptor for polymer solar cells. NI-T-NI exhibits a good crystallinity and can form H-aggregates in the solid state. NI-T-NI has a rather high-lying LUMO level, which is beneficial for achieving a high Voc. In cooperation with a high-lying LUMO level polymer PCDTBT-C12, a PCE of 2.01% with a high Voc of 1.30 V has been achieved. As far as we know, a Voc of 1.30 V is the highest value reported for single junction organic solar cells. Our results have demonstrated that 1,8-naphthalimide could be a useful building block for the synthesis of promising acceptor materials for polymer solar cells.

A series of new conjugated polymers (P1–P3) with 3,6-difluorocarbazole as a donor unit and benzoxadiazole as an acceptor unit were synthesized and used as donor materials for polymer solar cells (PSCs). The morphology of blend films was regulated by controlling the drying process via tuning the solubility of polymers and using solvent additives. Enhancing the solubility of polymers via increasing the volume of side chains can decrease the domain size of polymers and using 1,8-diiodooctane (DIO) as a solvent additive can give an even better vertical phase separation, leading to a significant enhancement of the power conversion efficiency (PCE) of up to 5.71% for P3 based PSCs. The improving of the interface between polymers and PC71BM phases as well as the formation of vertical phase separation after using DIO as an additive are probably responsible for the high open circuit voltage (Voc) of devices.

Three novel copolymers P1–3 with alkylthiophenyl substituted benzodithiophene as the donor unit, thiophene as the spacer, and benzothiadiazole as the acceptor unit have been designed, synthesized, and used as donor materials for polymer solar cells. Polymer solar cells with P3:PC71BM blends as the active layer exhibited a high power conversion efficiency (PCE) of 7.7% and a good tolerance to the change of film thickness. PCE higher than 7.3% can be obtained with the thickness of the active layer ranging from 90 to 380 nm, indicating that P3 is a very promising donor material for practical application.

Two conjugated polymers with benzodithiophene derivatives as the donor unit and planar difluoro-substituted dibenzo[a,c]phenazine as the acceptor unit P1, P2-L and P2-H were designed, synthesized, and used as the donor material in polymer solar cells. P2-H exhibits the highest hole mobility of 1.54 × 10−2 cm2 V−1 s−1. Polymer solar cells (PSCs) with a blend of P1:PC71BM (1 : 1.5, by weight) as the active layer show the highest power conversion efficiency (PCE) of 6.0% with an open circuit voltage (Voc) of 0.74 V, a short circuit current (Jsc) of 12.50 mA cm−2, and a fill factor (FF) of 0.65.

To develop novel hole-transport materials (HTMs) with less synthetic steps is still a great challenge. Here, a small molecule hexakis[4-(N,N-di-p-methoxyphenylamino)phenyl]benzene (F-1) was successfully synthesized by a relatively simple scenario. F-1 exhibits a deep highest occupied molecular orbital energy level of −5.31 eV. Notably, F-1 also features 2 times higher hole mobility of 4.98 × 10–4 cm2 V–1 s–1 than that of the mostly used 2,2′,7,7′-tetrakis(N,N-bis(4-methoxyphenyl)amino)-9,9′-spirobifluorene (spiro-OMeTAD). Consequently, F-1-based perovskite solar cells (PSCs) show markedly improved performance compared with spiro-OMeTAD-based ones. These results indicate such a material can be a promising HTM candidate to boost the overall performance of the PSC.

A series of conjugated polymers P0, P5, and P7 containing 0, 5, and 7 mol % 2,5-difluorobenzene units, respectively, were prepared and utilized as electron donors in polymer solar cells. Incorporation of a small amount of 2,5-difluorobenzene unit into the backbone of donor polymers can significantly increase their planarity and crystallinity as well as decrease their solubility. The improved molecular conformation can markedly affect the morphology of polymer:PC71BM blend films. After incorporation of 5 mol % 2,5-difluorobenzene unit into the backbone of donor polymers, the domain size of blend films became smaller and the hole mobility increased. Increasing the content of 2,5-difluorobenzene to 7 mol % can further decrease the solubility of resulting polymers and resulted in poor solution processability. As a result, P5-based devices achieved a power conversion efficiency (PCE) of 8.5%, whereas P0 based devices gave a PCE of 7.8%.

A kind of new fused-ring electron acceptor, IDT-OB, bearing asymmetric side chains, is synthesized for high-efficiency thick-film organic solar cells. The introduction of asymmetric side chains can increase the solubility of acceptor molecules, enable the acceptor molecules to pack closely in a dislocated way, and form favorable phase separation when blended with PBDB-T. As expected, PBDB-T:IDT-OB-based devices exhibit high and balanced hole and electron mobility and give a high power conversion efficiency (PCE) of 10.12%. More importantly, the IDT-OB-based devices are not very sensitive to the film thickness, a PCE of 9.17% can still be obtained even the thickness of active layer is up to 210 nm.

We have developed a kind of novel fused-ring small molecular acceptor, whose planar conformation can be locked by intramolecular noncovalent interaction. The formation of planar supramolecular fused-ring structure by conformation locking can effectively broaden its absorption spectrum, enhance the electron mobility, and reduce the nonradiative energy loss. Polymer solar cells (PSCs) based on this acceptor afforded a power conversion efficiency (PCE) of 9.6%. In contrast, PSCs based on similar acceptor, which cannot form a flat conformation, only gave a PCE of 2.3%. Such design strategy, which can make the synthesis of small molecular acceptor much easier, will be promising in developing a new acceptor for high efficiency polymer solar cells.

Fluorine is one of the human body's required trace elements. Imbalanced fluoride levels severely affect the normal functioning of living organisms. In this article, an anion-regulated synthetic nanochannel is described. A fluoride-driven ionic gate was developed by immobilizing a fluoride-responsive functional molecule, 4-aminophenylboronic acid, onto a single conical polyimide nanochannel. When the ionic gate was in the presence of fluoride, the boron bound F-, and the hybridization of the boron center changed from sp2 to sp3. Thus, negatively charged monofluoride adduct (RB(OH)2F-), difluoride adduct (RB(OH)F2-), and trifluoride adduct (RBF3-) modified surfaces with different wettability would be formed successively by increasing the concentration of F-. On the basis of the variation of surface charge and wettability, the nanochannel can actualize reversible switching between the "off" state and the "on" state in the absence and presence of F-, respectively. As an anion-regulated synthetic nanochannel, this fluoride-driven ionic gate was characterized by measuring ionic current, which possesses high sensitivity, fine selectivity, and strong stability. Thus, this gate may show great promise for use in biosensors, water quality monitoring, and drug delivery.

A new donor-acceptor-acceptor (D-A-A) type of conjugated molecule, N-(4-(N',N'-diphenyl)phenylamine)-4-(4'-(2,2-dicyanovinyl)phenyl) naphthalene-1,8-dicarboxylic monoimide (TPA-NI-DCN), consisting of triphenylamine (TPA) donors and naphthalimide (NI)/dicyanovinylene (DCN) acceptors was synthesized and characterized. In conjunction with previously reported D-A based materials, the additional DCN moiety attached as end group in the D-A-A configuration can result in a stable charge transfer (CT) and charge-separated state to maintain the ON state current. The vacuum-deposited TPA-NI-DCN device fabricated as an active memory layer was demonstrated to exhibit write-once-read-many (WORM) switching characteristics of organic nonvolatile memory due to the strong polarity of the TPA-NI-DCN moiety.

Three donor–acceptor (D–A) alternating conjugated polymers with silafluorene as the donor unit, 5-alkyloxy-6-fluorobenzothiadiazole as the acceptor unit, and thiophene as the spacer has been synthesized and used as donor materials for polymer solar cells (PSCs). The introduction of a fluorine atom on the benzothiadiazole unit can lower the HOMO and LUMO energy level of the resulted polymers to afford higher open circuit voltage (Voc); whereas the introduction of a flexible alkyloxy chain on benzothiadiazole unit can increase the solubility of the resulted polymers without interfering the close packing of polymer chains in the solid state. High molecular weight polymers P-1a, P-1b, and P-1c, which are fully soluble in 1,2-dichorobenzene (DCB) at elevated temperature, have been prepared by Suzuki polycondensation. Among these polymers, P-1c exhibited the highest hole mobility up to 1.36 × 10–2 cm2 V–1 s–1. PSCs based P-1b:PC71BM demonstrated the highest Voc up to 0.98 V. P-1a:PC71BM based PSCs gave the high...

Four novel conjugated polymers (P1-4) with 9,10-disubstituted phenanthrene (PhA) as the donor unit and 5,6-bis(octyloxy)benzothiadiazole as the acceptor unit are synthesized and characterized. These polymers are of medium bandgaps (2.0 eV), low-lying HOMO energy levels (below -5.3 eV), and high hole mobilities (in the range of 3.6 × 10(-3) to 0.02 cm(2) V(-1) s(-1) ). Bulk heterojunction (BHJ) polymer solar cells (PSCs) with P1-4:PC71 BM blends as the active layer and an alcohol-soluble fullerene derivative (FN-C60) as the interfacial layer between the active layer and cathode give the best power conversion efficiency (PCE) of 4.24%, indicating that 9,10-disubstituted PhA are potential donor materials for high-efficiency BHJ PSCs.

9-Arylidene-9H-fluorene containing donor-acceptor (D-A) alternating polymers P1 and P2 were synthsized and used for the fabrication of polymer solar cells (PSCs). High and low molecular weight P1 (HMW-P1 and LMW-P1) and high molecular weight P2 were prepared to study the influence of molecular weight and the position of alkoxy chains on the photovoltaic performance of PSCs. HMW-P1:PC71BM-based PSCs fabricated from 1,2-dichlorobenzene (DCB) solutions showed a power conversion efficiency (PCE) of 6.26%, while LMW-P1:PC71BM-based PSCs showed poor photovoltaic performance with a PCE of only 2.75%. PCE of HMW-P1:PC71BM-based PSCs was further increased to 6.52% with the addition of 1,8-diiodooctane (DIO) as the additive. Meanwhile, PCE of only 2.51% was obtained for P2:PC71BM-based PSCs. The results indicated that the position of alkoxy substituents on the 9-arylidene-9H-fluorene unit and the molecular weight of polymers are very crucial to the photovoltaic performance of PSCs.

Three novel isoindigo based donor–acceptor (D–A) conjugated polymers P1–3 have been synthesized by Suzuki polycondensation and utilized as donor materials for polymer solar cells (PSCs). These three polymers are of the same backbone, but have different substituents. All these polymers exhibit high thermal stability and broad absorption in the range of 300 to 770 nm. Hole mobilities of polymer films spin coated from 1,2-dichlorobenzene (DCB) solutions are 7.00 × 10−4, 2.37 × 10−3 and 2.90 × 10−4 cm2 V−1 s−1 for P1, P2 and P3, respectively. PSCs based on P2:PC71BM (1 : 2 by weight) with a 2% DIO additive displayed a power conversion efficiency (PCE) of 3.41% with a short-circuit current density (Jsc) of 7.57 mA cm−2, an open-circuit voltage (Voc) of 0.85 V, and a fill factor (FF) of 53%, under the illumination of AM 1.5G (100 mW cm−2). XRD diffraction measurements have shown that these polymers have a short π–π stacking distance in the solid state. The results demonstrate that these conjugated polymers could be promising donor materials in the application of polymer solar cells.

To achieve 5,6-difluorobenzothiadiazole and 2,7-linked silafluorene based soluble conjugated polymers, flexible side chains were attached at different positions of the conjugated polymers. Three soluble polymers PSiF-D(OT)DFBT, PSiF-TTDFBT, and PDOSiF-DTDFBT were prepared and used as donor materials for polymer solar cells. PSiF-D(OT)DFBT exhibits a band gap of 2.06 eV with a deep HOMO of −5.64 eV. PSiF-TTDFBT shows a band gap of 1.75 eV with the HOMO of −5.23 eV. PDOSiF-DTDFBT is of a band gap of 1.86 eV with the HOMO level of −5.37 eV. Among these three polymers, PDOSiF-DTDFBT shows the highest field effect transistor (FET) hole mobility up to 3.31 × 10−2 cm2 V−1 s−1, PDOSiF-DTDFBT:PC71BM blend films show the highest SCLC mobility up to 5.10 × 10−4 cm2 V−1 s−1, and polymer solar cells (PSCs) with the blend of PDOSiF-DTDFBT:PC71BM (1 : 1, by weight) as the active layer gave a power conversion efficiency (PCE) of 4.03% with an open circuit voltage (Voc) of 0.73 V, a short circuit current (Jsc) of 8.55 mA cm−2, and a fill factor (FF) of 0.65. Our studies also reveal the structure–property relationship of 2,7-linked silafluorene and 5,6-difluorobenzothiadiazole based conjugated polymers.

A round robin study across 15 laboratories in China was carried out using single junction devices with an active area of 1 cm(2) and differently sized small module with an active area of 20 and 24 cm(2) respectively. The devices represented the state of the art in terms of processing as they did not employ indium or vacuum and were prepared using only printing and coating techniques on flexible substrates. The devices were studied in their flexible form and thus approach the vision of what the polymer solar cell is. The main purpose of the work was to establish and chart geographic and cultural differences in what constitutes a competent IV-characterization procedure and also to establish the spread in measured data across the globe. The main finding is that efficiency data deviated up to 30% from the mean while an overall relative standard deviation of 12% was observed. Collating this spread with previous findings points toward a seemingly region-independent i.e. global observation of the uncertainty in the /Vcharacterization of a polymer solar cell. Finally, we highlight what might be done to improve the accuracy of the reported data. (C) 2013 Elsevier B.V. All rights reserved.

Alcohol soluble fullerene derivative (FN-C60) has been synthesized and used as a cathode interfacial layer for high-efficiency polymer solar cells (PSCs). To examine the function of the FN-C60 interfacial layer, polymer solar cells were fabricated with blends of P3:PC71BM, HXS-1:PC71BM, PDFCDTBT:PC71BM, and PDPQTBT:PC71BM as the active layer. In comparison to the bare Al electrode, power conversion efficiencies (PCEs) of P3:PC71BM, HXS-1:PC71BM, PDFCDTBT:PC71BM, and PDPQTBT:PC71BM based PSCs were increased from 3.50 to 4.64%, 4.69 to 5.25%, 2.70 to 4.60%, and 1.52 to 2.29%, respectively, when FN-C60/Al was used as the electrode. Moreover, the overall photovoltaic performances of PSCs with the FN-C60/Al electrode were better than those of cells with LiF/Al electrode, indicating that FN-C60 is a potential interfacial layer material to replace LiF.

The synthesis, characterization, and photophysical and photovoltaic properties of two anthracene-containing wide-band-gap donor and acceptor (D-A) alternating conjugated polymers (P1 and P2) are described. These two polymers absorb in the range of 300-600 nm with a band gap of about 2.12 eV. Polymer solar cells with P1:PC71 BM as the active layer demonstrate a power conversion efficiency (PCE) of 2.23% with a high Voc of 0.96 V, a Jsc of 4.4 mA cm(-2) , and a comparable fill factor (FF) of 0.53 under simulated solar illumination of AM 1.5 G (100 mW cm(-2) ). In addition, P2:PC71 BM blend-based solar cells exhibit a PCE of 1.42% with a comparable Voc of 0.89 V, a Jsc of 3.0 mA cm(-2) , and an FF of 0.53.

6,7-Dialkoxy-2,3-diphenylquinoxaline based narrow band gap conjugated polymers, poly[2,7-(9-octyl-9H-carbazole)-alt-5,5-(5,8-di-2-thinenyl-(6,7-dialkoxy-2,3-diphenylquinoxaline))] (PCDTQ) and poly[2,7-(9,9-dioctylfluorene)-alt-5,5-(5,8-di-2-thinenyl-(6,7-dialkoxy-2,3-diphenylquinoxaline))] (PFDTQ), have been synthesized by Suzuki polycondensation. Their optical, electrochemical, transport and photovoltaic properties have been investigated in detail. Hole mobilities of PCDTQ and PFDTQ films spin coated from 1,2-dichlorobenzene (DCB) solutions are 1.0 × 10−4 and 4.1 × 10−4 cm2V−1 s−1, respectively. Polymer solar cells were fabricated with the as-synthesized polymers as the donor and PC61BM and PC71BM as the acceptor. Devices based on PCDTQ:PC71BM (1:3) and PFDTQ:PC71BM (1:3) fabricated from DCB solutions demonstrated a power conversion efficiency (PCE) of 2.5% with a Voc of 0.95 V and a PCE of 2.5% with a Voc of 0.98 V, respectively, indicating they are promising donor materials.

With the efficient synthesis of the crucial dibenzopyran building block, a series of PDBPTBT polymers containing different alkyl side chains and/or fluorine substitution were designed and synthesized via the microwave-assisted Suzuki polycondensation. Quantum chemistry calculations based on density functional theory indicated that different substitutions have significant impacts on the planarity and rigidity of the polymer backbones. Interestingly, the alkyloxy chains of PDBPTBT-4 tend to stay in the same plane with the benzothiadiazole unit, but the others appear to be out of plane. With the S···O and F···H/F···S supramolecular interactions, the conformations of the four polymers will be locked in different ways as predicted by the quantum chemistry calculation. Such structural variation resulted in varied solid stacking and photophysical properties as well as the final photovoltaic performances. Conventional devices based on these four polymers were fabricated, and PDBPTBT-5 displayed the best PCE of 5.32%. After optimization of the additive types, ratios, and the interlayers at the cathode, a high PCE of 7.06% (V

Five polymer donors with distinct chemical structures and different electronic properties are surveyed in a planar and narrow-bandgap fused-ring electron acceptor (IDIC)-based organic solar cells, which exhibit power conversion efficiencies of up to 11%.

A ternary-blend strategy is presented to surmount the shortcomings of both fullerene derivatives and nonfullerene small molecules as acceptors for the first time. The optimal ternary device shows a high power conversion efficiency (PCE) of 10.4%. Moreover, a significant enhancement in PCE (≈35%) relative to both of the binary reference devices, which has never been achieved before in high-efficiency ternary devices, is demonstrated.

Lettuce-like CuxS micron particles were successfully prepared by a colloidal hot-injection method, and the preliminary evaluation of the light-gating artificial ionic nanochannels designed using these particles was also demonstrated. A likely underlying mechanism behind the formation of the lettuce architecture was tentatively proposed via monitoring the evolution process. These particles are hydrophobic and possess a high surface area that can readily absorb the light-responsive 1,3,3-trimethylindolino-6′-nitrobenzopyrylospiran (Spiro) molecules. Finally, the heterogeneous nanochannels were constructed by spin-coating the preprepared CuxS particles loaded with Spiro onto the commercially available anodic alumina (AAO) substrate. The AAO-CuxS/Spiro heterogeneous nanochannels “close” under illumination of ultraviolet light (365 nm) and then “open” by visible light irradiation, which exhibits a regulated ionic transport property with good responsive switchability and stability.

Four small molecular acceptors (SM1-4) comprising a central benzene core, two thiophene bridges and two 1,8-naphthalimide (NI) terminal groups were designed and synthesized by direct C-H activation. SM1 has a planar chemical structure and forms H-aggregation as films. By attachment of different substituents on the central benzene ring, the dihedral angles between the two NI end groups of SM1-4 gradually increased, leading to a gradual decrease of planarity. SM1-4 all possess a high-lying LUMO level, matching with wide band gap (WBG) polymer donors which usually have a high-lying LUMO level. When used in OSCs, devices based on SM1 and WBG donor PCDTBT-C12 gave higher electron mobility, superior film morphology and better photovoltaic performance. After optimization, a PCE of 2.78% with a V(oc) of 1.04 V was achieved for SM1 based devices, which is among the highest PCEs with a V(oc) higher than 1 V. Our results have demonstrated that NI based planar small molecules are potential acceptors for WBG polymer based OSCs.

Four ethynylene-containing donor-acceptor alternating conjugated polymers P1–P4 with 2,5-bis(dodecyloxy) substituted phenylene or carbazole as the donor unit and benzothiadiazole (BTZ) as the acceptor unit were synthesized and used as donor polymers in bulk heterojunction polymer solar cells. The optical, electrochemical, and photovoltaic properties of these four polymers with the ethylene unit located at different positions of the polymer chains were systematically investigated. Our results demonstrated that absorption spectra and the HOMO and LUMO energy levels of polymers could be tuned by varying the position of the ethynylene unit in the polymer chains. Photovoltaic devices based on polymer/PC71BM blend films spin coated from chloroform and dichlorobenzene solutions were investigated. For all four polymers, open circuit voltages (Voc) higher than 0.8 V were obtained. P4, with ethynylene unit between BTZ and thiophene, shows the best performance among these four polymers, with a Voc of 0.94 V, a Jsc of 4.2 mA/cm2, an FF of 0.40, and a PCE of 1.6%. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Luminogens exhibiting reversible multicolored emission switching in the solid state have been seldom reported, though they are of theoretical and practical importance. Through introduction of weak interaction to the propeller-like molecules, we obtained two tetraphenylethene derivatives exhibiting morphology dependent multicolored emissions. The emissions of the two compounds could be switched reversibly among three colors in the solid state by reversible transformation among three different aggregation states of the luminogens when treated with different stimuli. Hence a possible strategy to construct luminogen exhibiting reversible multicolored emission swithching is disclosed.

Three D–A alternating copolymers P1–3 with 3,7-linked 2,8-bis(alkoxy)dibenzothiophene as the donor unit and benzothiadiazole (P1 and P2) or 3,4-bis(octyloxy)benzothiadiazole (P3) as the acceptor unit have been designed and synthesized. P1–3 show two broad absorption peaks in the visible region, and the internal charge transfer (ICT) absorptions at about 530 nm in solutions and 560 nm in films of P3 are much stronger than that of P1 and P2. All the polymers show narrow band gaps below 2.0 eV and the low-lying HOMO energy levels of approximately −5.30 eV. The hole mobilities of polymer films spin-cast from 1,2-dichlorobenzene (DCB) solutions are 3.0 × 10–4, 2.7 × 10–4, and 2.3 × 10–3 cm2 V–1 s–1 for P1, P2, and P3, respectively. Under simulated solar illumination of AM 1.5G (100 mW/cm2), a PCE of 4.48% with a Voc of 0.83 V, a Jsc of 9.30 mA/cm2, and an FF of 0.58 has been achieved for PSCs with the P3:PC71BM blend (1:3, by weight) as the active layer in simply processed devices, whereas after the optimizati...

A new alternating copolymer (PSFDTBT) based on spirobifluorene, thiophene, and benzothiadiazole units has been synthesized. PSFDTBT has an optical band gap of 1.97 eV with the low-lying HOMO energy level at −5.4 eV. The hole mobility of the pristine PSFDTBT film spin-cast from o-dichlorobenzene (DCB) solution is 7.26 × 10–3 cm2 V–1 s–1 with on/off ratios in the order of 105. Polymer solar cell devices based on the blend films of PSFDTBT and PC71BM show a high open-circuit voltage of 0.94 V and a power conversion efficiency of 4.6% without any post-treatment. All the device measurements were performed in air without encapsulation. This is the first report on spirobifluorene-based conjugated polymers used for polymer solar cells, demonstrating the great potential of spirobifluorene moiety as an electron-donating unit for the construction of main chain donor–acceptor alternating conjugated polymers for high performance polymer solar cells.

Two kinds of polyfluorenes bearing two lateral pyrene terminated alkyl chains and two alkyl chains per repeating unit were synthesized by Suzuki polycondensation and used to disperse single-walled carbon nanotubes (SWCNT) in organic solvents. Stable polymer-SWCNT complex can be formed via the multivalent π-π stacking interaction of the lateral pyrene functional groups and the polyfluorene backbone with the outer surface of carbon nanotubes; meanwhile the lateral alkyl chains can impart good solubility to the complex. As expected, polyfluorenes bearing lateral pyrene functional groups and octyl chains exhibited much higher carbon nanotube solubility in common organic solvents than the corresponding polyfluorenes bearing only octyl chains. Photophysical studies indicated that the formation of polymer-SWCNT complex can effectively quench the fluorescence of polyfluorenes.

Fluorene-based polymers containing perfluorooctyl moieties were designed and synthesized. The high electronegativity and F…H-C interactions are present in the fluorinated polymers, which slightly induce blue-shift of UV-Vis absorption in film. The fluoropolymer films prepared from fluorinated solvents show lager contact angles than those prepared in non-fluorinated solvents.

A series of donor-acceptor (D-A) alternating copolymers (P1, P2 and P3) with thiophene -benzothiadiazole-thiophene-triphenylamine main chain have been synthesized by Suzuki poly-condensation. P1, P ...

A set of monodisperse 2,7-linked carbazole oligomers (3-mer, 5-mer, 7-mer, and 9-mer) was synthesized, and their photophysical, electrochemical, and thermal properties were investigated. In solutions, these oligomers exhibited bright blue emission with almost quantitative fluorescence quantum yield. The emission spectra of these oligomers in films are quite different. 3-Mer and 5-mer exhibited featureless emission spectra, whereas 7-mer and 9-mer showed well-resolved emission spectra.

A novel donor-acceptor copolymer containing 9-alkylidene-9H-fluorene unit in the main chain, poly[9-(1-hexylheptylidene)-2,7-fluorene-alt-5, 5-(4,7-di-2-thienyl-5,6-dialkoxy-2,1,3-benzothiadiazole) ...

Silole-containing conjugated polymers (P1 and P2) carrying methyl and octyl substituents, respectively, on the silicon atom were synthesized by Suzuki polycondensation. They show strong absorption in the region of 300–700 nm with a band gap of about 1.9 eV. The two silole-containing conjugated polymers were used to fabricate polymer solar cells by blending with PC61BM and PC71BM as the active layer. The best performance of photovoltaic devices based on P1/PC71BM active layer exhibited power conversion efficiency (PCE) of 2.72%, whereas that of the photovoltaic cells fabricated with P2/PC71BM exhibited PCE of 5.08%. 1,8-Diiodooctane was used as an additive to adjust the morphology of the active layer during the device optimization. PCE of devices based on P2/PC71BM was further improved to 6.05% when a TiOx layer was used as a hole-blocking layer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

A planar conjugated copolymer named HXS-1 was applied in thin film phototransistors. Similar to organic field-effect transistors using V(G) to control the source-drain current, in phototransistors, the light is used to substitute V(G) as an independent variable to control the output of the transistors to realize light detection and signal magnification in a single organic device. All devices exhibited high performance with an on/off ratio up to 4.6 × 10(4) (the highest on/off ratio of organic or polymer phototransistors), which could be assigned to i) the wide absorption features of HXS-1 in the whole UV-vis range, ii) the ideal HOMO energy level of HXS-1 (5.21 eV) to align with Au electrodes (5.2 eV) and iii) the high mobility of the polymer thin films (∼0.06 cm(2) /Vs). Moreover, the devices, both under continuous operation conditions and long term measurement conditions, exhibited excellent stability, indicating potential applications of the devices in polymer-based optoelectronics.

Herein, the relationship between the supramolecularly self-assembled nanostructures and the chemical structures of coil-rod-coil molecules is discussed. A series of nonamphiphilic coil-rod-coil molecules with different alkyl chains, central mesogenic groups, and chemical linkers were designed and synthesized. The solvent-mediated supramolecular self-assembling of these coil-rod-coil molecules resulted in rolled-up nanotubes, nanofibers, submicron sized belts, needle-like microcrystals, and amorphous structures. The self-assembling behaviors of these coil-rod-coil molecules have been systematically investigated to reveal the relationship between the supramolecularly self-assembled nanostructures and their chemical structures. With respect to the formation of rolled-up nanotubes by self-assembly of coil-rod-coil molecules, we have systematically investigated the following three influencing structural factors: 1) the alkyl chain length; 2) the central mesogenic group; (3) the linker type. These studies disclosed the key structural features of coil-rod-coil molecules for the formation of rolled-up nanotubes.

In this feature article, we present a short review on the recent development in the construction of structurally perfect red and blue light-emitting materials and highlight such research in our group. We focus mainly on the three-dimensional conjugated structures such as dendrimers, hyperbranched polymers, star polymers, spirobifluorene-based polymers, and spiro-bridged ladder-type oligomers and polymers. Results indicated three-dimensional conjugated structures can efficiently decrease the aggregation of materials, resulting in the improving of the light-emitting efficiency.