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All polymer solar cells (APSCs) have attracted considerable attention due to their unique advantages such as flexibility and mechanical stability. However, their poor charge mobility and difficulty in accurately optimizing phase separation structures have limited their performance improvement. Here, we achieved a multilength scale morphology control of the molecular local orientation and component distribution of the J51:N2200 blend by adding a volatilizable solid additive Bipy to the blend. Since Bipy was more compatible with J51 than N2200, J51 could be enriched on the bottom surface. During thermal annealing, with evaporation of Bipy across the thin thickness direction, Bipy has more chance to contact N2200. The repulsive force between Bipy and NDI2OD units of N2200 enhanced the chain planarity of N2200 and the connectivity between crystalline lamellae. This dual role of Bipy in J51:N2200 contributes to increases of the charge mobility and more balanced charge transfer simultaneously. Meanwhile, the rate of charge recombination decreases and charge extraction increases which result in an efficient PCE of 8.73%.

The active layer morphology with a domain size of 10–20 nm and large interfacial area plays a significant role in governing the device power conversion efficiency (PCE) of semitransparent polymer solar cells (ST-PSCs). However, the unbalanced aggregation rate of a polymer donor and a near infrared non-fullerene acceptor led to a large phase separation domain. In order to inhibit the intense aggregation of a non-fullerene acceptor, a third component which increases the nucleation and growth barrier of the non-fullerene acceptor can be added to balance aggregation leading to a suitable domain size of donors and acceptors. In order to verify our idea, PTB7-Th and non-fullerene acceptor IEICO-4F were selected as a model system. IEICO-4F tends to form strong aggregation due to its planar conformation. In order to suppress the intense aggregation, an amorphous molecule NCBDT-4Cl which has good miscibility with IEICO-4F is added to increase the nucleation barrier of IEICO-4F because NCBDT-4Cl can be dispersed evenly in the IEICO-4F phase. In situ UV-vis absorption spectra were recorded to monitor the nucleation and growth process of IEICO-4F during the drying process. The results show that the growth time of IEICO-4F is reduced to 45 s from 122 s by incorporating 20 wt% NCBDT-4Cl, resulting in reduced aggregation of IEICO-4F. The small IEICO-4F aggregates disperse in the PTB7-Th matrix and form refined bicontinuous pathways. The optimized ternary ST-PSCs achieve a PCE of 10.31% with an average visible transmittance (AVT) of 20.6%.

A high performance near-infrared organic phototransistor is achieved via introducing a small molecule acceptor as an electron trapping site into the narrow-bandgap conjugated polymer films. With only 10% (wt) addition of the acceptor molecule, the photoresponse to light of 850 nm has been significantly improved with a best photoresponsivity up to 2000 A W-1, high detectivity of 1016 Jones and fairly good photosensitivity in the order of 106.

Understanding the key factors influencing the mechanical and electrical properties of semiconducting polymers is crucial to the development of stretchable electronics. In this work, a high-mobility...

The influences of combined torsion-tension deformation on the microstructural evolution and corrosion resistance of 316L stainless steel were investigated. The microstructure and corrosion behavior of the deformation samples were studied in detail. The results showed that the grains were more significantly refined under combined deformation than under tensile deformation. However, further increase in pre-torsion led to little change in grain size. The results of transmission electron microscopy and corrosion tests results indicated that high-density dislocations were detrimental, whereas the corrosion resistance, grain refinement and deformation twins were beneficial to corrosion resistance. Furthermore, the effect of deformation twins on corrosion resistance was greater than that of dislocation density, which, in turn, was greater than the influence of grain size.

Commercial applications of skin-like electronic devices for healthcare, intelligent robotics and electronic communication require large-scale high-density transistor arrays with high mechanical deformability and robustness that can be provided by intrinsically stretchable transistors. However, the contradictory crystallinity-dominated mobility and stretchability in the currently reported polymer semiconductors result in extremely limited high-mobility intrinsically stretchable transistors. Herein, based on a polymer with strong intrachain transport, we pioneer the use of molecular weight modulation to synchronously achieve increased mobility from 0.56 to 1.95 cm2 V−1 s−1 and increased crack-onset strain from 26 to 97% in the PIDTBT film. Based on the molecular weight modulation, a high-performance intrinsically stretchable transistor array with stretchability up to 100 percent strain and mobility up to 1.84 cm2 V−1 s−1, was demonstrated. Moreover, the stretchable transistor array presents a device density as high as 375 devices per square centimeter and good electrical performance at the static and dynamic stretching strain. Our results provide a new strategy for creating intrinsically stretchable transistors with high mobility and present unprecedented opportunities for large-scale high-density production of next-generation stretchable electronics.

Four wide bandgap donor-acceptor (D-A) conjugated polymers, i.e. P-diF2T, P-TT, P-BDT and P-NDT, with bis(5-(2-decyltetradecyl)-[2,3′-bithiophen]-2′-yl)arylenes as D-units and 2-propyl-5,6-difluorobenzo[d][1,2,3]triazole (ffTAZ) as A unit were synthesized for photovoltaic applications. In P-diF2T, P-TT, P-BDT and P-NDT, 3,3′-difluoro-2,2′-bithiophene (diF2T), thieno[3,2-b]thiophene (TT), benzo[1,2-b:4,5-b']dithiophene (BDT) and naphtho[1,2-b:5,6-b']dithiophene (NDT) were used as aryl central units, respectively, to adjust the properties of the polymers. The optical bandgap is 1.83 eV for P-diF2T, 1.85 eV for P-TT, 1.90 eV for P-BDT and 2.04 eV for P-NDT. All four polymers show temperature-dependent aggregation behavior in solution, and their absorption spectra are complementary with that of non-fullerene acceptor (NFA) 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(5-hexylthiophen-2-yl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC-Th). Polymer solar cells (PSCs) based on these polymers and ITIC-Th were fabricated and characterized. Power conversion efficiencies (PCEs) higher than 7% were demonstrated for all polymers. The devices based on P-diF2T exhibited the highest PCE up to 10.08% with a high fill factor (FF) of 0.741. The good photovoltaic performance of P-diF2T is attributed to the synergies of the low-lying highest occupied molecular orbital (HOMO) energy level of the polymer and the favorable microstructures and morphology and thereby high and balanced charge carrier mobilities of the blend films. This study suggested that adjusting aromatic D units together with using alkylthiophene as side chains is an effective approach to design donor polymers for high performance PSCs based on NFA.

Two isomeric 2-hexyl substituted five-ring-fused asymmetric thienoacenes, i.e., thieno[1]benzothieno[3,2-b][1]benzothiophene (BTBTT6), in which the S atom in the terminal thiophene ring is located at different positions relative to the BTBT core, were synthesized and characterized. The syn-isomer forms bilayer “head-to-head” structures with herringbone packing modes within the layers in crystals, while the anti-isomer shows “head-to-tail” single-layer structures and sandwich-herringbone packing within the layers. The difference in packing structures involved the fact that the syn-isomer has stronger intermolecular interactions than the anti-isomer. Importantly, organic thin-film transistors (OTFTs) with near-ideal transfer and output characteristics were fabricated. Mobilities in the saturation and the linear regime (μsat and μlin) of up to 11.7 and 10.6 cm2 V−1 s−1, respectively, were achieved for the syn-isomer. This is the first report on OTFTs with both μsat and μlin above 10 cm2 V−1 s−1.

Four bisisoindigo (bis-IID) derivatives containing different numbers of electron withdrawing fluorine (F) or nitrogen (N) atoms and eight alternating copolymers of them with 2,2′-bithophene (BT) or 3,3′,4,4′-tetrafluoro-2,2′-bithiophene (4FBT) were synthesized. Depending on the numbers of F and N atoms incorporated, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of the polymers were feasibly tuned in the ranges of −5.51 to −6.06 eV and −3.64 to −4.01 eV, respectively. Top gate and bottom contact (TGBC) organic thin-film transistors (OTFTs) were fabricated to study the semiconducting properties of the polymers. Five polymers, i.e., P0F-BT, P2F-BT, P4F-BT, P2N2F-BT, and P0F-4FBT that contain 0–4 F and N atoms in the repeating unit, with HOMO and LUMO energy levels above −5.90 and −3.80 eV, respectively, all showed ambipolar OTFT characteristics. Three other polymers P2F-4FBT, P4F-4FBT, and P2N2F-4FBT that contain 6 or 8 F and N atoms with HOMO ...

A series of naphthalene carbohydrazone based fluorescent chemosensors L1-L4 were developed for the detection of Zn2+ by significant fluorescence enhancement. The binding ratio of the L1-Zn2+ complex was determined by a Job’s plot to be 1:1 and confirmed by ESI–MS studies. The corresponding of the L1-Zn2+ ensemble was elucidated through X-ray crystallography along with spectroscopic studies. Furthermore, the LX-Zn2+ (X = 1–2) complexes can specifically detect pyrophosphate (PPi) in HEPES buffer solution through fluorescence quenching. The detection limit of LX-Zn2+ (X = 1–2) for PPi sensing were calculated to be as low as 2.54 ppb and 0.94 ppb, respectively. In addition, due to their good cell membrane permeability and low cytotoxicity, L1-L4 have been applied to sequentially detect Zn2+ and PPi in living cells. More importantly, the electronic effect of substitute groups on fluorescence signaling have been studied by substituent properties ranging from electron-donating to electron-withdrawing, which sets up a promising strategy for the rational design of fluorescent sensors.

We herein report the synthesis and characterization of four asymmetric conjugated oligomers based on polycyclic aromatics, i.e. , 2-(5-hexylselenophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene (BTBT-S6), 2-(5-hexylfuryl-2-yl)[1]benzothieno[3,2-b][1]benzothiophene (BTBT-F6), 2-(5-hexylselenophen-2-yl)[1]benzoselenopheno[3,2-b][1]benzoselenophene (BSBS-S6) and 2-(5-hexylfuryl-2-yl)[1]benzofuro[3,2-b][1]benzofuran (BFBF-F6), for elucidating the influence of chalcogens on molecular geometries, electronic structures, thin film microstructures and the performance of organic thin-film transistors (OTFTs). Compared to the previously reported analogue 2-(5-hexylthiophen-2-yl)[1]benzothieno[3,2-b][1]benzothiophene (BTBT-T6), all four molecules have higher-lying highest occupied molecular orbital (HOMO) energy levels. BTBT-S6 and BSBS-S6 (S replaced by Se atoms) display similar mesomorphic behavior and packing motif in solid state. However, BSBS-S6 shows much poorer crystallinity. Only crystal phase was observed for BTBT-F6 and BFBF-F6 (S replaced by O atoms). These two molecules also adopt the molecular arrangements, film growth modes and film morphology distinct from BTBT-S6 and BSBS-S6. Thus, the four molecules exhibited very different OTFT performance. BTBT-S6 showed the highest mobility of 4.68 cm 2 V −1 s −1 and all other three compounds exhibited mobilites lower than 1 cm 2 V −1 s −1 .

Hydrazine has been identified as an environmental contaminant and a probable human carcinogen for its high toxicity. Thus, the development of detection methods for mapping hydrazine in solution and biosystems, particularly in vivo, is of great significance. Here, through firstly exploited 2-thiophenecarbonyl moiety as a recognition unit for hydrazine, a novel near-infrared (NIR) fluorescent probe CyOS is obtained based on hemicyanine. The probe shows high selectivity towards hydrazine over various amino acids and common ions with a significant fluorescence enhancement at 701 nm in the presence of hydrazine. Further, it has a sufficiently low detection limit (0.78 ppb). And most importantly, due to its good cell membrane permeability and low cytotoxicity, CyOS has been applied to monitor and image hydrazine in living cells, tissues and mice. To the best of our knowledge, it is the first time to visualize hydrazine in deep living tissues (∼90 μm).

The phase separation structure evolution process, i.e. confinement and broke out phenomenon in crystallization/crystallization poly (3-hexylthiophene) (P3HT) and poly [[N,N-bis(2-octyldodecyl)-napthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]- alt-5, 5′-(2,2′-bithiophene)] (N2200) blends were controlled by the polymer solution aggregation behavior and relative crystallization degree of each component. In this study, two different molecular weight of P3HT, Mw = 6 kDa and Mw = 55 kDa were selected and blend with N2200 as the model systems. Different molecular weight of P3HT had different crystalline ability in blend films. A similar phase separation of both two polymer blends could form in good solvent chloroform (CF). Marginal solvents and thermal annealing were employed to change the polymer solution aggregation behavior and relative crystallization degree of the two components. On one hand, when p-xylene (pX) was added as the co-solvent to increase the aggregation of P3HT molecules, for P3HT (Mw = 6 kDa)/N2200, the P3HT phase broke the restriction of N2200 phase while there was almost unchanged in P3HT (Mw = 55 kDa)/N2200. On the other hand, during thermal annealing, the P3HT molecule had a stronger molecular moving ability in P3HT (Mw = 6 kDa)/N2200 than that in P3HT (Mw = 55 kDa)/N2200 (the relative crystallization degree of these two polymers in P3HT (Mw = 6 kDa)/N2200 and P3HT (Mw = 55 kDa)/N2200 are 142 and 3, respectively). The pristine phase separation of P3HT (Mw = 6 kDa)/N2200 was destroyed effectively due to the unmatched crystallization degree of the two components and large sized fibrous phase separation was formed during thermal annealing. However, the pristine phase separation was almost unchanged in P3HT (Mw = 55 kDa)/N2200, and the P3HT molecule could partly ordered arrangement, which probably come from the almost matched crystallization degree of these two polymers. The results indicate that it is the Gibbs free energy that controls the phase separation in different relative crystallization degree. And different chain entanglements behavior was likely to be the main source of the morphological stability.

Three new alternating copolymers containing 3,3′-dicyano-2,2′-bithiophene (BT2CN), i.e., DPPTh-BT2CN, DPPPy-BT2CN and 2FIID-BT2CN based on diketopyrrolopyrrole (DPP) and isoindigo (IID) derivatives, were synthesized. The properties of these three polymers were compared with those of the reference polymer without a cyano (CN) group, DPPTh-BT. The introduction of CN groups dramatically lowered both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of the polymers. DPPTh-BT2CN exhibited HOMO and LUMO energy levels of −5.41 and −3.67 eV, respectively, which are much lower than those of the analogue polymer DPPTh-BT comprising a biothiophene (BT) segment. DPPPy-BT2CN and 2FIID-BT2CN showed even lower HOMO and LUMO levels, which are −5.83 and −3.75 eV for DPPPy-BT2CN and −6.15 and −3.92 eV for 2FIID-BT2CN. Organic thin-film transistors (OTFTs) were fabricated to evaluate the semiconducting properties of the polymers. DPPTh-BT2CN-based OTFTs exhibited electron-dominant transport characteristics, similar to the devices based on the benchmark n-type conjugated polymer N2200. By contrast, DPPPy-BT2CN and 2FIID-BT2CN-based devices displayed pure n-channel characteristics due to their lower HOMO and LUMO levels. All three polymers displayed an electron mobility (μe) of ca. 0.3 cm2 V−1 s−1, which is comparable to that of N2200 when the same device structure and measurement conditions were adopted.

We investigated the variations in solution-processed thin films containing pure diketopyrrolopyrrole-containing oligothiophene (SMDPPEH) or SMDPPEH blended with [6,6]-phenyl C61 butyric acid methyl ester (PCBM) under the different annealing temperatures. The optical properties, microstructures, and surface morphologies of the two types of thin films were characterized with UV–vis absorption spectra, grazing incidence X-ray diffraction (GIXRD), and atomic force microscopy (AFM). SMDPPEH thin film annealed at 100 °C exhibited a blue-shift of absorption maximum (λmax) peaks. GIXRD results of two types of films showed that (100) diffraction peak intensities were enhanced by increasing annealing temperatures and their shapes were changed from dot to arc when annealing temperatures were beyond 100 °C. AFM results showed that the films grain sizes increased as annealing temperature increased. AFM results also showed obvious large-size phase segregation in the films as annealing temperature increased to 125 °C. These results indicated that the crystallinity improved with increasing annealing temperature and a phase transition occurred in SMDPPEH films at the annealing temperature of 100 °C. This phase transition may lead to maximum device performance.

Polyamic acid (PAA) fiber derived from 3,3′,4,4′-biphenyltetra-carboxylic dianhydride and p -phenylenediamine is prepared via dry-jet wet-spinning method. Polyimide (PI) fibers are obtained by applying two kinds of thermal treatment procedures on the PAA fibers. The evolution of fiber structure during thermal treatments is traced. And the influence of fiber structure on the mechanical properties is also studied. In Procedure I, the PAA fibers are heated from room temperature to 400 °C at 5 °C/min. As temperature increases from room temperature to 125 °C, relaxation behavior of PAA chains happens at first. Then, from 125 to 300 °C, imidization reaction occurs. Meanwhile, before the temperature reaches 250 °C, a significant degradation of PAA chains exists and makes the fibers too weak to measure. Crystals in fiber begin to form as temperature exceeds 250 °C and totally complete at 350 °C. The fracture strength and initial modulus of fiber are significantly improved with the formation of crystals and finally reach 0.83 GPa and 48.4 GPa at 400 °C, respectively. In Procedure II, the PAA fibers are isothermally treated at 250, 300, 350 and 400 °C for different times. When treated at 400 and 350 °C, both imidization and crystallization in fiber can happen simultaneously and complete in tens of seconds because of the high mobility of the polymer chains. While as treated at 300 and 250 °C, both these two processes are slowed down and the formation of crystals lags behind the imidization process. High crystallinity can be obtained under higher treatment temperature in a very short time. The mechanical properties of fiber highly depend on the treatment temperature rather than the treatment time. The fibers treated at 400 °C for 60 s show the highest fracture strength and initial modulus of 1.4 GPa and 70.0 GPa, respectively.

Growth of rubrene thin films at room temperature on bare SiO 2 substrates and on top of a α-quaterthiophene (α-4T) inducing layer on SiO 2 substrates was investigated. The rubrene thin films and α-4T inducing layers were prepared by vacuum deposition method and were characterized by atomic force microscopy and X-ray diffraction. Rubrene thin films directly deposited on SiO 2 substrates had a number of holes on their surface, while the ones grown on top of a α-4T inducing layer on SiO 2 substrates exhibited highly ordered morphology and structure. It was found that large-area and ordered rubrene thin films could properly match with the α-4T inducing layers in the prepared heterostructures. Two different rubrene film growth mechanisms were observed from results obtained for films with different thicknesses. We conclude that rubrene thin films prepared at low temperature using α-4T inducing layer on SiO 2 substrates hold a great promise of application in large-area and flexible displays.

Two new wide-bandgap polythiophenes, i.e., poly[5,5′-bis(2-hexyldecyl)-(2,2′-bithiophene)-4,4′-dicarboxylate-alt-5,5′-3-chloro-2,2′-bithiophene] (PDCBT-Cl) and poly[5,5′-bis(2-hexyldecyl)-(2,2′-bithiophene)-4,4′-dicarboxylate-alt-5,5′-3,3′-dichloro-2,2′-bithiophene] (PDCBT-2Cl) comprising 3-chloro-2,2′-bithiophene and 3,3′-dichloro-2,2′-bithiophene moieties, respectively, were synthesized for fullerene-free polymer solar cells (PSCs). For comparison, three other polymers based on [2,2′-bithiophene]-4,4′-dicarboxylate (DCBT), i.e., PDCBT, PDCBT-F, and PDCBT-2F with 2,2′-bithiophene, 3-fluoro-2,2′-bithiophene, and 3,3′-difluoro-2,2′-bithiophene as comonomers, respectively, were also prepared. PSC devices were fabricated with these polymers as donor materials and ITIC-Th1 as acceptor. The incorporation of chlorine (Cl) or fluorine (F) atoms into polymers both efficiently downshifted the highest occupied molecular orbital (HOMO) energy levels, leading to higher open-circuit voltage (Voc) in the PSCs. Owing to the proper phase-separated morphology with favorable molecular packing and miscibility, the device based on PDCBT-Cl:ITIC-Th1 exhibited efficient exciton dissociation and charge collection as well as weak charge recombination and thereby displayed the best power conversion efficiency (PCE) up to 12.38%. The devices based on other polymers showed inferior PCEs (8.14% for PDCBT, 10.85% for PDCBT-F, 8.48% for PDCBT-2F, and 6.94% for PDCBT-2Cl). The monomers that are used to make PDCBT-Cl can be synthesized in relatively large scale from commercial available chemicals. All these indicate that PDCBT-Cl is a promising donor material for the large area fabrication of high-performance fullerene-free PSCs.

Organic field-effect transistors (OFETs) based on organic semiconductor material 2,7-dioctyl[1]benzothieno[3,2- b ] benzothiophene (C8BTBT) as the active layer were fabricated by using organic molecular beam deposition (OMBD) and solution-processed methods, in which the C8BTBT thin-film morphology could be well controlled. In OMBD method, C8BTBT thin-film morphology could be controlled by the thickness of organic semiconductor layer and the deposition rate, of which the high-quality C8BTBT thin film was obtained at a thickness of about 20 nm and at a deposition rate of 1.2 nm/min, resulting in an obvious mobility improvement from 2.8 × 10 −3 cm 2 V −1 s −1 to 1.20 cm 2 V −1 s −1 . While in the solution-processing, C8BTBT thin-film morphology and thickness are related to the spin-coating speed and the substrate position in spin coater, i.e. , in-centre and off-centre position. The off-centre spin-coating with an optimized speed produced large-size domain C8BTBT thin film and accordingly resulted in a mobility of 1.47 cm 2 V −1 s −1 . Furthermore, an additive polystyrene (PS) was added into C8BTBT solution could further improve the thin-film morphology with more metal-stable phase as well as improve the interface contact with the substrate SiO 2 , resulting in the highest mobility up to 3.56 cm 2 V −1 s −1 . The research suggested that C8BTBT-based OFETs with the mobility over 1.20 cm 2 V −1 s −1 could be fabricated by using both OMBD and solution-processed methods through the thin-film morphology and structure optimization, which shows the potential applications in high-performance flexible and printed electronics.

We demonstrated the crystallization assisted microphase separation of all-conjugated diblock copolymers poly (2,5-dihexyloxy- p -phenylene)-block-(3-hexylthiophene) (PPP-b-P3HT, denoted as BmTn). The crystallization and microphase separation are summarized in terms of the difference of aggregation in solvent and the crystallization temperatures of two blocks, respectively. B39T18 and B41T44 were selected, and crystalline nanowires were formed for B39T18 cast from non-selective solvent via the crystallization of PPP block overwhelming P3HT block. However, both microphase separation and crystallization occurred from selective solvent for PPP block, due to the enhanced aggregation of P3HT block governed by solvophobic interactions. The morphological evolution of B41T44 with equivalent crystallization capacity displayed an opposite result. The lamellar nanostructures formed in films were cast from non-selective solvent and the crystallization breakout microphase separation was formed from selective solvent. Besides, the evolution and phase transition in the thermal annealing process indicated that the PPP crystallized confined from the molten in the P3HT crystalline region, and then the P3HT breakout crystallized primarily and microphase separation with the molten PPP occurred.

A new metastable solvent-induced clathrate liquid crystalline phase of beta phase (named beta' here) in crystalline poly(9,9-dioctylfluorene) (PFO) thin film induced by solvent annealing is found by a combination of in situ ultraviolet and visible spectrophotometry (UV-vis), photoluminescence spectroscopy (PL), and grazing incidence wide-angle X-ray scattering (GIWAXS). The solvent annealing process consists of three processes: diffusion of solvent molecules into the film; saturation of solvent in the film; and drying of the film under nitrogen. The formation of beta' phase with ordered packing of side chains and disordered packing of backbones occurs during the diffusion process of solvent molecules into the film. When the solvent molecules penetrate the film, the disordered side chains start to align themselves to form an ordered structure, and the ordering would gradually in the saturation-process. Furthermore, the ordering of side chains drives an ordered rearrangement of the backbones during the drying process; however, the crystallinity of the side chains decreases with the orderly rearrangement of backbones due to the helical conformation of PFO.

The selection of sensitizer and its existence in the blend films are important to the performance of all-polymer ternary solar cells. Herein, all-polymer ternary solar cell devices, which used poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′] dithiophene-alt-3-fluorothieno[3,4-b]thiophene-2-carboxy-late] (PTB7-Th) as donor, poly[[N,N-bis(2-octyldodecyl)-napthalene-1,4,5,8-bis(dicarboximide)−2,6-diyl]-alt-5, 5′-(2,2′-bithiophene)] (N2200) as acceptor and poly[N−900-hepta-decanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole) (PCDTBT) as sensitizer, are successfully demonstrated. The intermolecular interaction between donor PTB7-Th and sensitizer PCDTBT may lead to aggregation of PTB7-Th which decreases domain sizes and enlarges D/A effective interface area. In addition, the PCDTBT molecules also extend light absorption and cascaded energy levels of the ternary blend system. As a result, with 15% PCDTBT we get a power conversion efficiency of 5.11%, almost 20% higher than control device due to more favored exciton dissociation and higher charge transport efficiency. This study reveals a promising way to achieve high efficiency all-polymer solar cells using a low-band gap polymer PCDTBT. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1811–1819

A polycyclic aromatic unit comprising six rings, i.e., 5,11-bis(2-octyldodecyl)dithieno[3,2-b:3′,2′-b′]naphtho[1,2-b:5,6-b′]dithiophene (DTNDT), was developed. Four donor–acceptor (D–A) conjugated polymers, which are named P-BT, P-2FBT, P-IID, and P-DPP, were synthesized with DTNDT as the D-unit and 2,1,3-benzothiadiazole (BT), 5,6-difluorobenzo[c][1,2,5]thiadiazole (2FBT), isoindigo (IID), and diketopyrrolopyrrole (DPP) as the A-unit, respectively. All four polymers are thermally stable with decomposition temperature above 390 °C and show pseudo-straight-shaped backbones. Their ordered thin films were prepared via solution spin-casting, in which conjugated backbones mainly adopted edge-on alignment on the substrate. The semiconducting properties of the polymers were characterized with bottom gate and top contact (BGTC) organic thin film transistors (OTFTs). All four polymers showed p-type transport behavior, and the hole mobilities were 0.023, 0.078, 0.50, and 1.80 cm2/(V s) for P-BT, P-2FBT, P-IID, and ...

Inverted organic solar cells (OSCs) have been fabricated using MoO3 doped N,N'-bis-(1-naphthyl)-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB:MoO3), MoO3 doped 4,4′-N,N'-dicarbazole-biphenyl (CBP:MoO3), and combined CBP:MoO3/NPB:MoO3 as anode modifying layers (AMLs), respectively. The CBP:MoO3/NPB:MoO3/anode increases fill factor of device than the NPB:MoO3/anode and CBP:MoO3/anode, mostly because the former enhances hole injection into photoactive layer than the latter two. The CBP:MoO3/NPB:MoO3/anode and CBP:MoO3/anode increase open-circuit voltage of device than the NPB:MoO3/anode, due to the larger work function of CBP:MoO3 than that of NPB:MoO3. It is also found that combined CBP:MoO3/NPB:MoO3 enhances short-circuit current density of device than single NPB:MoO3 and CBP:MoO3, mainly ascribed to the fact that the former improves absorptance of device than the latter two. As a result, the CBP:MoO3/NPB:MoO3/anode improves power conversion efficiency of device than the NPB:MoO3/anode and CBP:MoO3/anode. We present a useful concept to develop high-performance AMLs for inverted OSCs.

The orientation transition and self-epitaxial crystallization of all-conjugated diblock copolymers poly(p-phenylene)-block-(3-hexylthiophene) (PPP-b-P3HT) were systematically investigated by in situ temperature-resolved two-dimensional grazing incidence X-ray diffraction (2D GIXD) in step-by-step heating and cooling process. B39T18 was selected; the results of 2D GIXD showed that the PPP block crystal adopted a face-on orientation while the crystallization of P3HT block was hindered in as-casted films. Three different molecular orientations transition were obtained in self-epitaxial crystallization circles. First, P3HT crystallize with edge-on during the heating process and induced the PPP blocks crystallized with edge-on during the cooling process. Then, the as-casted film was heated in the melting temperature region of PPP blocks and isothermally crystallized. The partial melting of PPP blocks promoted the P3HT blocks crystallize in a face-on due to the steric limitation effect; PPP blocks crystallized ...

A series of weak donor-strong acceptor polymers containing two different electron-deficient units (diketopyrrolopyrrole and thienoisoindigo) are synthesized and used in broad-response and high-detectivity polymer photodetectors. By adjusting the composition ratio of the two acceptors, the absorption spectra, energy levels, molecular stacking, and film morphology are affected, which in turn influence the photodetector performance. With increased thienoisoindigo component, the HOMO energy levels shift from -5.41 to -4.76 eV, and the LUMO energy levels are nearly unchanged, corresponding to reduced bandgaps and red-shifted absorption spectra. 1,8-Diiodooctane additive shows greatly impact on the film morphology, which affects the photodetector performance significantly. Going from P1 to P5, the detectivity decreases, but the response range increases. The photodetector based on P4 exhibits detectivity of greater than 10(11) Jones in a broad spectral region of 300-1200 nm, which is really promising for UV-vis-NIR light detection.

We report the formation of β-phase nanofibers of poly(9,9-dioctylfluorene) (PF8) in aged toluene solution at low temperature and link their photophysical properties and rheological behaviors with the solution structures. By cooling the PF8 toluene solution and subsequently aging, the PF8 chains develop into nanofiber morphology and the effects of aging time, temperature, and solution concentration on the nanofiber formation are investigated. The formation and development process of PF8 β-phase in aged solution captured by TEM has not been reported in previous studies. Further increasing the solution concentration leads to the gelation of PF8 after aging at low temperature. It is interesting to show that a scaling law correlating specific viscosity with the polymer concentration and intrinsic viscosity originally proposed for flexible polymer solutions also exists for this semiflexible PF8 polymer solution. This study may offer an effective way to improve the understanding of the formation mechanism of PF8 β-phase and facilitate the ongoing exploration of using such nanofiber networks in electronic devices. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 633–639

Oligo(2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene)s Tn and Tn-2CN (n = 4, 8, 12, 20, n represents the number of thiophene rings), which have H and CN end-groups, respectively, were synthesized, and the effect of chain-length and end-groups on their properties was studied. For both Tn and Tn-2CN, a red-shift of absorption spectra was observed as the chain length increased. Introduction of electron-withdrawing CN end-groups resulted in a remarkable red-shift of absorption spectra in both solution and film states for shorter oligomers (n = 4 and 8). However, for oligomers with n = 12 and 20, obvious red-shift of absorption spectra was only observed in the film state. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels were both lowered by introducing CN end-groups, and the level of reduction decreased with an increase of the chain length. Both the chain length and end-groups influenced the thin film microstructures of the oligomers as revealed by two-dimensional grazing incidence X-ray diffraction (2D-GIXD) and atomic force microscopy (AFM) studies. The oligomers with n = 4 and 8 stood on the substrates with a tilt angle, and the films of T4-2CN and T8-2CN were characterized with 3D crystal structures. In contrast, the oligomers with n = 12 and 20 adopted an edge-on arrangement with the long axes of the molecules parallel to the substrates, like polymeric counterparts. Compared to the films of T12 and T20, those of T12-2CN and T20-2CN comprised larger and more oriented crystal-domains to the substrates along with shorter lamellar distances. Charge-transport properties of the oligomers were influenced by both the chain length and end-groups due to their remarkable effect on the film morphology and packing structures. The film of T8-2CN combined three features: large domain sizes, low surface-roughness and diminished grain boundaries, and therefore exhibited the highest field-effect mobility.

Polymorphs of vanadyl-phthalocyanine (VOPc) films were realized on the polymer-modified substrates. Balanced ambipolar transport was observed in the Phase II of VOPc film on the PMMA modified substrate, while only electron transport was obtained on PVA layer. The different transport behavior is believed to be original from their crystalline structures, which may lead to their different energy-band structures.

Hydrozirconation on vinyl-terminated substrates (silicon wafer and nanosilica sphere) is employed as an efficient way for immobilization of zirconocene catalyst through Zr-C bonds, which is applied in surface coordination ethylene polymerization producing surface-tethered polyethylene (PE). The formation of Zr-C σ bond induced by hydrozirconation provides an initiator precursor for growing a layer of PE covalently linked onto substrates. The results from SEM, AFM, and TEM show that the surface polymerization is controlled by hydrozirconation. Surface pattern or core-shell structure with crystalline PE coating can be formed, when silicon wafer is selectively functionalized with vinyl-groups or vinyl-modified nanosilica is applied. It is believed that hydrozirconation for the synthesis of zirconocene initiator can be a versatile route to prepare polyolefin hybrid materials.

The effect of thermal treatment on the transition of molecular packing and orientation of the semiconducting poly(2,5-dihexyloxy-p-phenylene) (PPP) film is probed by the combination of in situ 2D grazing incidence X-ray diffraction (2D GIXD) and selected area electron diffraction (SAED). The structure analysis indicates that PPP crystallizes in an orthorhombic unit cell with a = 21.20 angstrom, b = 3.78 angstrom, and c = 4.24 angstrom. A variation of the annealing temperature from 80 degrees C to 100 degrees C demonstrates that the worm-like morphology in the pristine film melts and develops into nanowires. Furthermore, the molecular orientation transforms from face-on to edge-on via thermal annealing. Remarkably, a previously unknown metastable state of slope edge-on with a tilt angle of 51.1 degrees is observed. This orientation change arises from the heterogeneous nucleation and growth of edge-on PPP crystal during crystallization from the melt.

The P3HT thin films were made by novel solvent vapor assisted spin-coating method that adds several opened bottles of solvent into spin-coater and seals it with a lid. Such thin films directly had broader absorption and higher crystallinity. The corresponding thin film transistor had higher mobility of 0.041 cm(2) V-1 s(-1) contrasting to 0.007 cm(2) V-1 s(-1) of device based on P3HT thin film made by normal spin-coating. Compared with the solvent vapor annealed P3HT thin film made by normal spin-coating, the thin film made by solvent vapor assisted spin-coating has similar absorption spectrum, X-ray diffraction and device performance, which demonstrates that such novel method is equivalent to the combination of normal spin-coating and solvent vapor annealing. However the fabrication is more simple and the process time is reduced from several hours to several tens of seconds, which is more beneficial for actual mass production. (C) 2013 Elsevier B.V. All rights reserved.

Polyoctylfluorene thin films were made using novel solvent vapor assisted spin-coating method, which adds solvent into spin-coater and seal it for several minutes before spin-coating to form a solvent vapor atmosphere. The absorption, photoluminescence spectra, electroluminescence spectra and X-ray diffraction patterns demonstrate that β phase directly generate in such thin film while the thin film made by using normal method is amorphous, which means such method combines normal spin-coating and solvent vapor annealing together into one simply and fast process. The brightness and efficiency of related electroluminescence device are also enhanced due to the self-dopant effect.

Although polycationic surfaces have high antimicrobial efficacies, they suffer from high toxicity to mammalian cells and severe surface accumulation of dead bacteria. For the first time, we propose a surface-initiated photoiniferter-mediated polymerization (SI-PIMP) strategy of constructing a "cleaning" zwitterionic outer layer on a polycationic bactericidal background layer to physically hinder the availability of polycationic moieties for mammalian cells in aqueous service. In dry conditions, the polycationic layer exerts the contact-active bactericidal property toward the adherent bacteria, as the zwitterionic layer collapses. In aqueous environment, the zwitterionic layer forms a hydration layer to significantly inhibit the attachment of planktonic bacteria and the accumulation of dead bacteria, while the polycationic layer kills bacteria occasionally deposited on the surface, thus preserving the antibacterial capability for a long period. More importantly, the zwitterionic hydrated layer protects the mammalian cells from toxicity induced by the bactericidal background layer, and therefore hierarchical antibacterial surfaces present much better biocompatibility than that of the naked cationic references. The dominant antibacterial mechanism of the hierarchical surfaces can switch from the bactericidal efficacy in dry storage to the bacteria repellent capability in aqueous service, showing great advantages in the infection-resistant applications.

The film morphology, structure, and electrical properties of lead phthalocyanine (PbPc) epitaxially grown on 5,5 ''-bis(3'-fluoro-biphenyl-4-yl)-2,2':5',2 ''-terthiophene (m-F2BP3T) inducing layer substrates were systematic investigated. The morphologies of PbPc films sensitively depend on the thickness of the inducing layer and substrate temperature. All the epitaxial PbPc films with high quality presented the triclinic form with a variation of the out-of-plane orientation. The field-effect mobility of the epitaxial PbPc films was 0.05-0.31 cm(2)/V s, which was significantly improved by 1-2 orders of magnitude compared to the traditional films. The evolution of the device performance is the synergistic effect of the morphology and out-of-plane orientation of the triclinic form of PbPc. The higher quality of the films and the smaller ratio of (100)/(001), the higher device performance is. A clear relationship between the morphology, structure, and the performance of epitaxial PbPc-based organic field-effect transistors was reported. (C) 2012 Elsevier B.V. All rights reserved.

New large-size poly(3-butylthiophene) (P3BT) spherulites are obtained by solution aging. These P3BT spherulites are composed of nanoribbons, and the P3BT molecules arrange into Form II structure with a backbone pi-stacking distance of 0.47 nm. P3BT lamellae adopt "flat-on" orientation at the edge of the spherulite, and the spherulite preferentially grows along the pi pi stacking direction. These spherulites could be obtained in bulk solution or at the top or bottom of the solution, depending on the competition of gravity and Brownian motion. Temperature-dependent photoluminescence spectra demonstrate that the polymer chains are arranged in H-aggregation model. The 00 transition in UVvisible absorption spectra blue shifts from 2.03 eV (610 nm, Form I) to 2.11 eV (589 nm, Form II). These results provide a further understanding of the crystallization and photophysical properties of poly(3-alkylthiophene) (P3AT), and the preparation method of large size and pure P3AT spherulites shows potential in applications of organic electronics.

As spin-coating polyoctylfluorene (PFO) thin films were thermally annealed at various temperatures and their photoluminescence, electroluminescence and crystalline nanostructure was characterized. α phase PFO generate when annealing temperature reaches 80 °C and the performance of corresponding electroluminescence device was dramatically enhanced due to the self-doping effect. As the annealing temperature increases, the photoluminescence and electroluminescence decrease. Both in out-of-plane and in-plane grazing incident X-ray diffraction pattern the PFO thin film annealed at higher temperature has stronger diffraction peaks, indicating higher degree of crystallinity. The formation of vacancy defects and increase of interface roughness in crystalline process is considered as the reason for the reduction of luminescence. These results show that the electro-optical properties of PFO can be enhanced through controlling annealing temperature to form α phase PFO in low degree of crystallinity.

We report the manageable formation of the gradient-layered poly(3-hexylthiophene) and [6,6]-phenyl C61-butyric acid methyl ester (P3HT/PCBM) blend film by spin coating via introducing bathocuproine (BCP) into the mixed P3HT/PCBM solution. The BCP can improve the aggregation and thereby the preferential precipitation of PCBM during the spin-coating process, leading to the gradient-layered phase separation of P3HT and PCBM. The regular solar cells using the gradient-layered ternary blend films gave poor photovoltaic performance, due to the mismatch between the polarity of the regular-device structure and the vertical composition profile of the ternary blend film. By contrast, in the inverted solar cell, the gradient-layered ternary blend film could provide the increased device performance over the conventional bulk heterojunction binary blend films.

PFO thin films made of toluene solution dissolved for 12, 30 and 80 min at 55 °C were prepared and then treated by solvent vapor annealing or thermal annealing. Their absorption, photoluminescence, electroluminescence and morphology were characterized. The results show that the thin film made of solution dissolved for short time contains trace β phase PFO that lead to unusual emission. After solvent vapor annealing or thermal annealing, luminescence of such thin film is lower than that made of solution dissolved for long time. The surface morphology shows that such thin film contains large aggregations with size of 120 × 80 nm, which is in line with the light scattering results of 120 nm large particles in the solution, indicating the difference of luminescence originate from the residue aggregations. Such aggregations will lead to stronger diffraction peak in the in-plane GIXRD and weaker diffraction peak in the out-of-plane GIXRD, which indicates they have more ordered structure in main chain direction that will hinder the formation of ordered packing of PFO molecular chains in out-of-plane direction. These results demonstrate that the PFO solution needs to be dissolved for enough time to realize repeatment of high quality light-emitting device for actual massive application.

Weak epitaxy growth (WEG) is an effective method in the preparation of high-mobility thin films of disk-like organic semiconductors. The growth behavior and quality of the epitaxial thin film are closely related to the inducing layers. Here, a series of fluorinated molecules, 5,5"-bis(3'-fluoro-biphenyl-4-yl)-2,2':5',2"-terthiophene (m-F2BP3T), 5,5"-bis(3',5'-difluoro-biphenyl-4-yl)-2,2':5',2"-terthiophene (F4BP3T), and 5,5"-bis(4'-fluoro-biphenyl-4-yl)-2,2':5',2"-terthiophene (p-F2BP3T) as well as a referenced molecule 5,5"-bis(biphenyl-4-yl)-2,2':5',2"-terthiophene (BP3T), are introduced to serve as inducing layers for the epitaxy growth of phthalocyanine. Compared to the nonfluorinated inducing layer, the interactions between the fluorinated inducing layer and phthalocyanine might be relatively strong due to the potential existence of C-H···F weak hydrogen bonds. The growth behavior and mechanism of phthalocyanine on the fluorinated inducing layers are investigated by atomic force microscopy (AFM), grazing incidence X-ray diffraction (GIXD), selected area electron diffraction (SAED). According to the AFM and SAED, H(2)Pc presents a selective epitaxy growth depending on the position of fluorine: epitaxy growth on m-F2BP3T and F4BP4T, and nonepitaxy growth on p-F2BP3T. Comparison of CuPc with F(16)CuPc on monolayer p-F2BP3T further revealed that the uncommon nonepitaxy growth behavior of H(2)Pc (CuPc) on p-F2BP3T mainly originates from the enhanced interactions between the two types of molecules. As a consequence, the capability of molecules orienting themselves along the surface channel is decreased; meanwhile, the demand of the upper limit of the lattice mismatch is more rigorous for commensurate epitaxy. Finally, the oriented nucleation of H(2)Pc (CuPc) on monolayer p-F2BP3T is affected, and netlike crystals are formed. The sudden change of H(2)Pc (CuPc) from multiorientation on monolayer to just one orientation on double-layer p-F2BP3T suggests that there is a critical lattice mismatch value for commensurate epitaxy in WEG when the molecule-substrate interactions are enhanced.

Inverted bottom-emission organic light emitting diodes (IBOLEDs) employing the electron injection structure of indium tin oxide (ITO)/1,4,5,8-naphthalene-tetracarboxylic-dianhydride (NTCDA)/Li2CO3 doped bathocuproine (BCP) (1: 4 Li2CO3: BCP) were fabricated, where NTCDA and BCP stand for NTCDA and BCP, respectively. The NTCDA on ITO was characterized crystalline and n-doped as a result of the interaction between ITO and NTCDA. Compared to the IBOLED using the electron injection structure of ITO/10 nm 1: 4 Li2CO3: BCP, the one utilizing the electron injection structure of ITO/3 nm NTCDA/7 nm 1: 4 Li2CO3: BCP showed the remarkable increases in both current density and efficiency, mainly due to the higher electron conductivity of n-doped NTCDA than that of n- doped BCP. The dependence of the current conduction in IBOLED on the thickness of NTCDA was investigated. We provide a simple method to significantly enhance the performance of IBOLEDs.

Evolution of BP2T films grown at the early stage was investigated using atomic force microscopy (AFM) and X-ray diffraction (XRD). The AFM results demonstrate that the BP2T grown on the SiO2 substrate transformed from a layer by layer growth to island growth when the coverage is higher than 3 ML. The out-of-plane and in-plane X-ray diffraction measurements reveal a phase transition from the thin film phase to the bulk phase suddenly occurs as the growth mode changes. A careful analysis of the structure evolution implies that not only the strain but also the soft matter property of the organic thin films are responsible for the thickness dependent evolution. Moreover, the thickness dependent structure and phase of BP2T films result in different morphologies of ZnPc grown on different layers of BP2T. The ZnPc crystals gradually changed from stripe-like to nanofiber-like, concomitantly with the epitaxy relationships from incommensurate epitaxy to commensurate epitaxy. Conversely, the diversity of ZnPc films also reflects different properties of the BP2T films with different numbers of layer, which cannot be obtained from the AFM or XRD. This study supplies a deeper insight into the thickness evolution of organic thin films and to the weak epitaxy growth.

Birefringent ring-banded spherulites with radial periodic variation of thicknesses were grown from poly(epsilon-caprolactone) (PCL) solutions under conditions for which the Solution concentration was held constant during the whole development of the morphology. The as-grown ring-banded spherulites were investigated by optical (OM) and atomic force (AFM) microscopies, by transmission electron microscopy (TEM) of samples sectioned parallel to the plane of film, and also by electron diffraction (ED) and grazing incidence X-ray diffraction (GIXD) techniques. The results indicate that the concentric rings in the birefringent ring-banded spherulites. as well as those in the nonbirefringent ring-banded spherulites, are a manifestation of periodic variation of thicknesses along the radius. The development of the ring-banded spherulites with radial periodic variation of thicknesses is due to periodic diffusion-induced rhythmic growth associated with periodical change in the concentration gradient in polymer solution with constant concentration. The morphological features reflect the competition between the diffusion flux of polymer chains in solution, J, and spherulitic growth with radial growth velocity. V, which call be characterized by the parameter delta = J/V. The effects of crystallization conditions, including polymer molecular weight, initial solution concentration, and solvent evaporation rate, oil the formation of ring-banded spherulites with radial periodic variation of thicknesses were studied.