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Developing a new strategy to obtain n-type organic semiconductors is crucial for the advance of organic electronics. We herein report the synthesis and investigation of a series of donor–acceptor-t...

The use of chalcogenophenes runs through the whole history of developing high performance π-conjugated materials toward organic electronics devices. In this work, we report three A–D–A′–D type (3E,7E)-3,7-bis(2-oxo-1H-pyrrolo[2,3-b]pyridin-3(2H)-ylidene)benzo[1,2-b:4,5-b′]difuran-2,6(3H,7H)-dione- (NBDO-) based π-conjugated copolymers containing different chalcogenophenes, i.e., 4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (TTT), 4,7-di(selenophen-2-yl)benzo[c][1,2,5]thiadiazole (STS), or 4,7-di(selenophen-2-yl)benzo[c][1,2,5]selenadiazole (SSS). The effects of chalcogen atom on their optoelectronic properties were explored by a range of techniques, including thermal, optical, electrochemical, computational, molecular aggregation, and carrier transport properties. Interestingly, both PNBDO-TTT and PNBDO-STS formed highly ordered, crystalline, and lamellar packing thin films with uniform intertwined fibrillar morphologies, whereas PNBDO-SSS only gave random molecular packing thin film with amorphous mor...

We report the synthesis and characterization of two novel difluorothienylethylene-bridged methyleneoxindole (FVTI) and methyleneazaoxindole (FVTAI) acceptor units and six FVTI- or FVTAI-based donor–acceptor (D–A) copolymers P1–P3F. On the basis of the optimized conjugated backbone conformations, we put forward the intramolecular noncovalent interactions existing in these copolymers and suggested that the fluorine and pyridine-nitrogen atoms could improve the polymeric backbone planarity by forming multiple conformation locks such as N···H, F···H, and F···S interactions, etc. Thin film microstructure investigations indicate the copolymers with more fluorine or pyridine-nitrogen atoms in their respective single D–A pair generally formed more orderly thin films. All the six copolymers exhibited p-type charge transport characteristics with increasing mobilities from P1 to P1F and P2 to P2F. On the contrary, P3F showed relatively lower mobility than that of P3, which was attributed to the higher hole injection...

Herein, we report the synthesis and characterization of a series of ambipolar cyanostyrylthiophene (CST)-based conjugated polymers without or with fluorine substituents, namely PD-CST, PD-3F-CST, PD-23F-CST, and PD-25F-CST. With the change of the number or incorporating position of fluorine substitutes on the novel CST unit, the electron mobilities of field-effect transistors based on these polymers dramatically increased from 0.0015 cm2 V–1 s–1 for PD-CST, 0.13 cm2 V–1 s–1 for PD-3F-CST, and 0.25 cm2 V–1 s–1 for PD-23F-CST to 0.53 cm2 V–1 s–1 for PD-25F-CST. AFM and GIXRD investigation indicated that the annealed PD-25F-CST thin film possesses stronger crystallization tendency and highly ordered lamellar packing than those of the other polymers. Further theoretical calculations and single-crystal X-ray diffraction analysis deeply revealed the remarkable influences of the number and incorporating position of fluorine substitutes on the frontier orbital energy levels, backbone conformation, and charge tran...

We develop two donor–acceptor copolymers based on a fluorinated dithienylethene building block, namely PNFDTE1 and PNFDTE2, in which naphthalenediimide (NDI) acts as an acceptor unit. Thermogravimetric analysis displayed both copolymers having good thermal stability with high decomposition temperatures over 400 °C. Broad absorption spectra were observed in the UV–vis–NIR region, with the absorption maxima being 720 and 724 nm for PNFDTE1 and PNFDTE2, respectively. Cyclic voltammetry tests exhibited deep-lying lowest unoccupied molecular orbital energy levels of ca. −4.0 eV. Two-dimensional grazing incidence X-ray diffraction patterns showed that different packing modes for two polymers result in the variation in charge transport properties. Backbone fluorination effectively decreases electron injection barrier, thereby facilitating electron mobility. An impressive electron mobility of 3.20 cm2 V–1 s–1 was achieved in air for PNFDTE1-based polymer field-effect transistors fabricated on the poly(ethylene te...

Constructing planar π-conjugated backbone is of critical importance for polymeric semiconductors to obtain high charge carrier mobility. In this regard, suitable introduction of noncovalent interactions is one of useful approaches. Herein, we report a series of donor–acceptor copolymers based on diethoxydithiophenethene (EDTE), namely PEDTEn (n = 1, 2, and 3), containing multiple O···H–C and S···O conformational locks, where the latter ones are supplied by the EDTE units. PEDTEn owns planar conjugated backbones with suitable HOMO energy levels (ca. – 5.20 eV) and strong absorption behaviors along with enhanced solution processability. High-performance field-effect transistors based on the copolymers exhibited a high hole mobility of up to 5.37 cm2 V–1 s–1, which is among the highest values of semiconducting polymers based on the concept of conformational locks. AFM and GIXRD experiments reveal that PEDTEn could form crystalline and close packing thin films with a π–π stacking distance of down to 3.78 A.

The diphenylethene moiety is a versatile building block that offers several chemically functionalizable sites, allowing easy modulation of electronic properties of the resulting polymers and providing numerous opportunities for discovering related structure–property relationships. In this study, we report a series of difluorodiphenylethene-based copolymers with noncovalent conformational locks for applications in polymer field-effect transistors. Different fluorination positions lead to different type of intra- and intermolecular interactions, backbone conformations, and eventually different device performances. 2,2′-Difluorodiphenylethene-based copolymers P2DFPE-n containing F···H–C conformation locks exhibit obviously enhanced hole mobilities of 1.3–1.5 cm2 V–1 s–1, whereas 3,3′-difluorodiphenylethene-based copolymers P3DFPE-n containing F···H–C and F···S conformation locks show lower mobilities of 0.2–0.4 cm2 V–1 s–1. AFM and 2D-GRXD investigations indicate that P2DFPE-n takes predominantly edge-on ori...

A nonplanar but conjugated heteroacene, biindeno[2,1-b]thiophenylidene (BTP), is employed to design and synthesize solution-processable polymer semiconductors for organic field-effect transistors (OFETs) applications first. By copolymerizing with isoindigo (IDG), diketopyrrolopyrrole (DPP), and naphthalenediimide (NDI) derivatives, three novel BTP-based copolymers (PBTP-IDG, PBTP-DPP, and PBTP-NDI) have been synthesized and characterized successfully. The results indicate that three BTP-based polymers exhibit broad absorption spectra and good solubility in most common solvents. Because of the dominantly electron-deficient contributions to the whole polymer backbones, the energy levels of the lowest unoccupied molecular orbitals are decreased to ca. −4.0 eV for all these polymers, thus exhibiting good electron affinities. Moreover, the deep-lying energy levels of the highest occupied molecular orbitals (HOMO) have been demonstrated for three BTP-based polymers, with the HOMO values ranging from −5.48 to −5...

We reported the synthesis, characterization, and field-effect transistor properties of two diketopyrrolopyrrole (DPP)-based π-conjugated copolymers PNDF3-T-DPP and PNDF3-BT-DPP by introducing napht...

Thieno[3,2-b]thiophene-bridged polymer semiconductor, P(BDT-TT-BO), featuring benzoxadiazole (BO) acceptor unit was designed and synthesized. P(BDT-TT-BO) showed broad absorption, in the wavelength range of 350–700 nm, and low highest occupied molecular orbital (HOMO) energy level (−5.31 eV). The benzoxadiazole-based polymer semiconductor exhibited very promising optoelectronic performance. Power conversion efficiency of the polymer solar cell with P(BDT-TT-BO) as donor reached 7.05%, which is the champion efficiency in benzoxadiazole containing conjugated polymers and comparable to that of the most efficient benzothiadiazole-based donor polymers. The sensitive dependence of carrier mobility on the annealing temperature of the polymer semiconductors was systematic studied. After annealing at 200 °C, P(BDT-TT-BO)-based polymer field effect transistor showed a mobility of more than 12 times that of unannealed devices, reached 0.023 cm2 V–1 s–1, with a high on/off current ratio of 2.7 × 105.

Two donor–acceptor (D–A) copolymers, PzNDTDTBT and PzNDTDTBO, using 4,9-bis(2-ethylhexyloxy)naphtho[1,2-b:5,6-b′]dithiophene as an electron-rich unit and benzodiathiazole (BT) or benzoxadiazole(BO) as an electron-deficient one, were designed and synthesized via a Pd-catalyzed Stille-coupling method. The acceptor units were varied from BT to BO for adjusting the energy levels and optimizing the structures of polymers. Both copolymers possess good solubility, high thermal stability, broad absorption, and low bandgap and exhibit not only high field-effect mobilities but also high photovoltaic properties. The hole mobilities reach 0.43 and 0.34 cm2 V–1 s–1 for PzNDTDTBT and PzNDTDTBO film, respectively. Bulk heterojunction solar cells fabricated by using PzNDTDTBT or PzNDTDTBO as electron donor and PC71BM as acceptor show a power conversion efficiency of 3.22% and 5.07%, respectively, under illumination of AM1.5G, 100 mW cm–2. Both the hole mobilities and PCEs are among the highest values in the current repor...

Two new dendronized nonlinear optical (NLO) polyfluorenes were synthesized with high azo-chromophore loading density by the introduction of high generation chromophore dendrons on the side chains. Thanks to the advantages of Sharpless’ click chemistry reaction, the dendrons were conveniently bonded to the backbone of polyfluorene with the conversion of 100%, although they were really very bulky. The new-formed triazole rings in the dendrons acted as suitable isolation groups to minimize the strong dipole−dipole interactions among the polar chromophore moieties to improve NLO effects, according to the results obtained from UV−vis spectra and order parameters. All the polymers were well characterized and exhibited good solubility, high thermal ability, wide optical window, and large NLO effects (up to 106.0 pm/V). In addition, the tested NLO results of these dendronzied polymers demonstrated a deviation from the dipolar frustration that typically limits the NLO effect in conventional chromophore/polymer com...

By modifying the synthetic procedure, the previous reported impossible approach was successfully utilized to construct new azo-chromophore-containing hyperbranched polymers (HP1 and HP2) from AB2 m...

A new series of polyquinoline copolymers (P1−P5) containing 9,9‘-spirobifluorene in the main chain were synthesized via Friedlander reactions. The emission colors of the polymers were readily tuned from blue to yellow by changing the conjugated counits. Excellent EL performances were obtained for P5, probably because the proper donor/acceptor pairs were rightly matched, and the charge transport was significantly balanced. The devices based on P5 showed a maximum external quantum efficiency of 0.63% and a maximum photometric efficiency of 1.85 cd/A (at a brightness of 140 cd/m2). Yellow-green EL with narrow full width at the half-maximum (fwhm < 70 nm) and the highest maximum luminance (1768 cd/m2) among the currently reported polyquinolines was obtained for P5.