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A simple strategy is developed to simultaneously release tensile strain and passivate defects in an FA-based perovskite using CsPbI3 QDs, achieving a PCE of 23.3%.

A self-assembled nanofibrillar conjugated polymer film is used to optimize the CsPbIBr2/hole-transporting layer interface. The obtained CsPbIBr2 solar cell demonstrates an efficiency of 11.05% with excellent long-term stability.

Polarized light sources play a significant role in a growing number of applications: from general illumination to highly efficient displays. Solution-processed polarized light-emitting diodes (pol-LEDs) have attracted remarkable interest because of the wide choice of emissive materials, capability to be solution-processed and easy fabrication. We first classify organic pol-LEDs into two categories according to their aligning techniques, including (1) alignment without an oriented substrate and (2) alignment on an oriented substrate. Recent progress in aligning techniques, emissive materials, substrate materials, device performances and polarizing properties is summarized. We also discuss pol-LEDs based on emissive materials of one-dimensional (1D) II–VI and lead halide perovskite nanomaterials. Finally, an outlook is provided on research trends in the development of solution-processed pol-LEDs.

Two acceptor–donor–acceptor small molecules based on a fused ring indacenodithieno[3,2-b]thiophene (IDTT) as a donor, and hemi-isoindigo units, methyleneoxindole (IDTT-MI) and thienylmethyleneoxindole (IDTT-T-MI) as acceptors were synthesized and characterized for application in solution-processed organic field-effect transistors. The incorporation of a thiophene bridge which extended the conjugation of the backbone maintained highly co-planar structures, and also endowed the small molecule with ordered crystalline structures and interconnected morphology. Consequently, IDTT-T-MI-based organic field-effect transistors exhibited a highest hole mobility of 0.80 cm2 V−1 s−1, which was the highest mobility for solution-processed hemi-isoindigo-based organic semiconductor materials.

Non-chlorinated solvents, especially polar non-chlorinated solvents, are highly desirable for the fabrication of organic field-effect transistors (OFETs) because they do not create environmental and health issues. In this paper, four polar non-chlorinated solvents, namely, tetrahydrofuran (THF), ethyl acetate (EtAc), acetone (AT), and 2-methyltetrahydrofuran (2-MTHF) were used to fabricate high-performance acceptor-donor–acceptor small molecules (IDTT–IDD-N) for OFETs. The effects of polar non-chlorinated solvents regarding optical properties, device performances, and microstructures were investigated in detail. High-performance OFETs were demonstrated with the hole mobilities of up to 1.01, 1.49, 2.40, and 0.81 cm2 V−1 s−1 for the THF, EtAc, AT, and 2-MTHF-processed devices, respectively. This work indicates that the IDTT–IDD-N-based OFETs fabricated from polar non-chlorinated solvents have potential applications in high-performance and environmentally friendly organic electronics.

Six donor–acceptor (D–A) conjugated polymers, P1–P6, based on the novel electron acceptors bis-isoindigo (BIID) and bis-azaisoindigo (BAID), were designed and synthesized for solution-processed organic field-effect transistors with high-performance optical and electrical properties. Energy level regulation was achieved by incorporation of nitrogen and fluorine heteroatoms and side chain optimization to reduce side chain density and extend branching point positions. Both the hole (μh) and electron mobilities (μe) significantly increased from P1 to P6, and there was an obvious transition from hole-dominated ambipolar charge transport behavior to highly-balanced ambipolar behavior. Since aza-substitution strengthened the electron-deficient property of the acceptor units, the entire molecular skeleton of BAID-based polymers has a high electron affinity and a low-lying lowest unoccupied molecular orbital (LUMO) level according to ultraviolet photoelectron spectroscopy (UPS) and cyclic voltammetry (CV) measurements. The μe of BAID-based polymers is an order of magnitude higher than that of BIID-based polymers. In addition, side chain optimization was shown to significantly influence intermolecular interactions and supramolecular self-assembly. The stepwise reduction of the π–π stacking distances of P1–P6 calculated by GIXRD curves supports this conclusion. Finally, in P6 (PBAID3-2FBT), a maximum absorption wavelength (λmax) was observed at 797 nm, a low optical band gap (Eg) of 1.27 eV, a low LUMO level of −3.90 eV, and an average μh and μe of 1.31 cm2 V−1 s−1. This paper offers an available molecular design strategy to achieve highly-balanced and high-performance ambipolar charge carrier transport D–A conjugated polymers.

A conjugated polymer based on naphthalene-diimide and dithiophene units was synthesized by continuous flow synthesis. Due to the large specific surface area and excellent heat transfer, the polymerization was completed within ∼35 min at 110 °C. Compared to flask synthesis, the continuous flow technology exhibited a high synthesis efficiency and significant reduction in reaction times. The polymer using flow synthesis exhibited higher molecular weight (17.28/35.27 vs. 4.86/13.21 kg mol−1), lower polydispersity indexes (2.0 vs. 2.7), and a more ordered crystalline structure. Consequently, much higher electron mobilities (0.74 vs. 0.11 cm2 V−1 s−1) with Ion/Ioff ratios of 106 were obtained for the polymer using flow synthesis. This study demonstrates that continuous flow synthesis will be promising in the preparation of conjugated polymers with high efficiency.

Photovoltaic power generation, as a rapidly growing new energy source, is a technology that uses a semiconductor to convert light energy into electrical energy. Sb2S3 solar cells possess the advantages of simple binary components, abundant resources, nontoxicity, and excellent stability; they have recently attracted extensive investigation interest. Various strategies, such as solution and vacuum deposition, have been used to fabricate functional layers, including Sb2S3 photoactive layers, electron transport layers and hole transport layers. Here, we briefly review the preparation methodologies, morphologies, structures, optoelectronic properties and the corresponding solar cell performance of functional layers for both planar heterojunction solar cells and mesoporous sensitized solar cells. Some viewpoints of further improvement of Sb2S3 solar cell conversion efficiency from the aspect of material fabrication and modification are given.

Achieving good electrical properties and ductility of polymer semiconductors has always been challenging. In this work, a series of isoindigo derivative-based conjugated polymers was studied in an effort to gain a better understanding of the influence of polymer main and side chain structures on their electrical and mechanical properties. The results suggested that the introduction of alkyl side chains onto the donors can significantly enhance the mechanical properties of isoindigo-based polymers; however, the electrical properties of the films greatly deteriorated due to the large steric hindrance by the chain. The insertion of strong electron-withdrawing units, such as benzodifurandione, into the isoindigo chain during the synthesis of a bis(2-oxoindolin-3-ylidene)-benzodifuran-dione (BIBDF)-based polymer (PBIBDF-BT) significantly boosted the electrical properties of the films without decreasing their mechanical properties. The crack onset in PBIBDF-BT thin films was observed at 50% tensile strain. In addition, PBIBDF-BT thin films exhibited bipolar transport properties with both electron and hole mobilities greater than 0.1 cm2 V−1 s−1 at 100% strain. It is found that the improvement of PBIBDF-BT performance is attributed to its proper molecular structure. The long alkyl side chains significantly increase the ductility of PBIBDF-BT thin films, and the strong electron-withdrawing BIBDF unit in the main chains enhances the local aggregation, resulting in a significant increase in mobility. These results indicate that the mechanical and electrical properties of conjugated polymers could simultaneously be improved through reasonable molecular design.

In this paper, a liquid crystal (LC) based tunable metamaterial absorber with dual-band absorption is presented. The proposed absorber is analysed both numerically and experimentally. The analysis shows that the two absorption peaks, originating from the new resonant structure, are experimentally detected at 269.8 GHz and 301.4 GHz when no bias voltage is applied to the LC layer. In order to understand the absorption mechanisms, simulation results for the surface current and power loss distributions are presented. Since liquid crystals are used as the dielectric layer to realize the electrically tunable absorber, a frequency tunability of 2.45% and 3.65% for the two absorption peaks is experimentally demonstrated by changing the bias voltage of the LC layer from 0 V to 12 V. Furthermore, the absorber is polarization independent and a high absorption for a wide range of oblique incidence is achieved. The designed absorber provides a way forward for the realization of tunable metamaterial devices that can be applied in multi-band detection and imaging.

A series of P3HT-b-PHA-b-P3HT tri-block and P3HT-b-PHA di-block copolymers were facilely synthesized in one pot. The influence of the block ratio on the optical, microstructural and electrical properties has been investigated. OFETs based on these block copolymers have been fabricated with an improved mobility of 0.052 cm2 V−1 s−1via a blending method.

A stripping procedure was demonstrated for the preparation of an ultra-smooth aluminum electrode. After potentiostatic anodization and treatment with a self-assembled monolayer (SAM) of n-octadecyl phosphonic acid, AlOx–SAM hybrid dielectrics were grown onto flexible, stripped aluminum combining low cost manufacture under ambient conditions with excellent dielectric characteristics (negligible leakage, 114.3 nF cm−2 capacitance). Field effect transistors using dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) as an organic semiconductor can be operated below −5 V with a high mobility of 0.53 cm2 V−1 s−1, high on/off current ratio of 1.7 × 105, low subthreshold slope of 210 mV dec−1, and good threshold of −1.51 V. Moreover, the DNTT transistor showed a good photoresponse to blue light with a wavelength of 450 nm, with photoresponsivity (R) of 50 A W−1 and a photocurrent/dark current ratio (P) of 5 at a light intensity of 5 μW cm−2.

The aldol reaction is a facile green synthetic method and has been widely used in the synthesis of small molecules. In this study, we attempted to prepare conjugated polymers using aldol polymerization for the first time. Two isoindigo-based conjugated polymers (PIID-DT and PBIBDF-DT) were synthesized successfully in excellent yields and with high molecular weights (MGPCn up to 53.9 kDa) using toluene as the solvent and an acid as the catalyst. The entire synthesis route is economical and environmentally friendly, and the traditional drawbacks such as the use of organometallic reagents, toxic tin monomers, and other environmentally harmful compounds often encountered in Stille and Suzuki cross-coupling reactions could be avoided. Moreover, the isoindigo-based polymers prepared by the newly established aldol polymerization were also evaluated as organic field-effect transistors with bottom-gate/top-contact devices and exhibited excellent mobilities as high as 0.16 and 0.26 cm2 V−1 s−1 with a high Ion/Ioff ratio of 105 for PIID-DT and PBIBDF-DT, respectively. Therefore, aldol polycondensation has environmentally friendly characteristics that can be applied in the green synthesis of isoindigo-based conjugated polymers.

Three donor–acceptor polymers based on (3E,7E)-3,7-bis(2-oxoindolin-3-ylidene)benzo-[1,2-b:4,5-b]-difuran-2,6(3H,7H)-dione (BIBDF) and three kinds of dialkylated bithiophenes with head-to-head (HH), head-to-tail (HT), and tail-to-tail (TT) connectivity were synthesized by the Stille coupling reaction. Their photophysical and electrochemical properties, electronic device performance, and microstructure were investigated. We found that the alkyl chains substituted near the thiophene–thiophene connection cause less steric hindrance than those near the BIBDF–thiophene connection. Therefore PBIBDF-HH exhibited the preferred planarity, crystallinity, and molecular orientation, yielding the highest field-effect mobility. A maximum electron mobility of 1.23 cm2 V−1 s−1 and a maximum hole mobility of 0.37 cm2 V−1 s−1 were obtained for PBIBDF-HH-based devices. These results show that the substitution sites on the bithiophene units play an important role in the determination of molecular organization and the resulting device performance.

The development of organic solid-state luminescent materials with continuously tunable emission is a topic of interest for both fundamental research and practical applications. A luminescent liquid crystal, (2Z,2′Z)-2,2′-(1,4-phenylenae)bis(3-(4-(dodecyloxy)phenyl)acrylonitrile) (PDPA) is reported, which exhibits a continuously tunable emission color from green to orange at room temperature when cooled from an isotropic liquid at different cooling rates. PDPA self-assembles to a layer structure and/or a helical structure with different pitch length depending on the stacking rate, which influences the conformation coplanarity. The conjugation lengths shorten and the π–π interactions weaken, inducing a photoluminescence spectrum blue-shift from 600 nm to 506 nm; a considerable luminescent shift. Therefore, this material has potential uses in novel optical devices, as its emission profile can be tuned by controlling the molecular aggregation.

Conjugated polymers based on a bis(2-oxoindolin-3-ylidene)-benzodifuran-dione (BIBDF) unit displayed promising performances for their application in organic thin-film transistors (OTFTs). Herein, three new BIBDF-based donor–acceptor (D–A) polymers, containing thieno[3,2-b]thiophene (TT), (E)-2-(2-(thiophen-2-yl)vinyl)thiophene (TVT) and (2-(thiophene-2-yl)alkynyl)thiophene (TAT) as donors, were synthesized and characterized. The results indicated that the donor unit plays important roles in affecting the absorption bands, HOMO levels, lamellar packing and π–π stacking distances of the BIBDF-based polymers. The OTFT devices based on the three polymers were fabricated, and their field-effect performance and environmental stability were also characterized. All three BIBDF based polymers showed good n-type field-effect characteristics. The PBIBDF-TT showed the highest electron mobility of 0.65 cm2 V−1 s−1 and the best environmental stability, while the PBIBDF-TAT showed the lowest electron mobility of 0.13 cm2 V−1 s−1. The corresponding crystalline structures and morphologies revealed that the PBIBDF-TT and PBIBDF-TVT showed close π–π distances and long-range ordered, lamellar crystalline structures both of which contributed to the high charge carrier mobility. The PBIBDF-TAT with close π–π distances but poor crystalline structures showed miserable performance. Overall, this work showed the correlation of the microstructures and properties of BIBDF-based polymers, and the field-effect performances can be effectively optimized by introducing different donor units.

A novel semiconductor–rubber–semiconductor (P3HT–PMA–P3HT) triblock copolymer has been designed and prepared according to the principle of thermoplastic elastomers. It behaves as a thermoplastic elastomer with a Young's modulus (E) of 6 MPa for an elongation at break of 140% and exhibits good electrical properties with a carrier mobility of 9 × 10−4 cm2 V−1 s−1. This novel semiconductor may play an important role in low-cost and large-area stretchable electronics.

An acceptor–π–acceptor (A1–π–A2) type polymer based on phthalimide and diketopyrrolopyrrole units has been designed and synthesized by Stille cross-coupling reaction. The photo-physical, electrochemical and transistor properties have been also investigated. The polymer exhibited broad absorption in the near infrared region and low LUMO/HOMO energy levels. Organic thin-film transistors (OTFTs) devices with common architectures were fabricated to evaluate the device properties. Polymer-based OTFTs devices exhibited n-type charge transfer under vacuum and yielded an electron mobility as high as 0.52 cm2 V−1 s−1. This is a record value for n-type polymers based on phthalimide structure. The OTFTs devices were also investigated in air and displayed p-type transporting behavior with a hole mobility of up to 0.13 cm2 V−1 s−1. The corresponding thin film morphology and polymer packing were also investigated in detail by atomic force microscopy (AFM) and X-ray diffraction (XRD) to correlate with the mobility. The results showed that the polymer film possessed highly uniform polymer nanofibers, a long-range-ordered lamellar structure and a small π–π stacking distance.

A photoresponsive polymer thin-film transistor based on a donor–acceptor conjugated polymer ambipolar semiconductor (PBIBDF-BT) is proposed in this report. The device exhibited both hole- and electron-carrier transport response to incident light with photoswitching speeds below 14 ms. In addition, the photocurrent/dark-current ratio and the photoresponsivity were 4552 and 108.43 mA W−1 for the p-type channel, and 1044 and 38.72 mA W−1 for the n-type channel, respectively. The PBIBDF-BT films exhibit more pronounced sensitivity to red light than previous polymer semiconductors, and the drain current gradually increased with an increase in the illumination intensity, resulting in typical output field-effect transistor characteristics. The influence of mobility of PBIBDF-BT thin films, which were formed via spin coating at different spinning speeds on the OTS/SiO2/Si substrate, on the phototransistor response to light illumination was further investigated.

A new thieno-isoindigo derivative, bis(5-oxothieno[3,2-b]pyrrole-6-ylidene)benzodifurandione (BTPBF) was synthesized by replacing the outer benzene ring of the isoindigo derivative (BIBDF) with thiophene. This was used for the first time as an acceptor to construct a donor–acceptor polymer (PBTPBF-BT) for organic thin-film transistors. The thermal stability, photophysical-, and electrochemical properties, microstructure, and transistor characteristics were also investigated. Compared to the isoindigo derivative-based polymer PBIBDF-BT, the thieno-isoindigo derivative-based polymer PBTPBF-BT had a much smaller bandgap (0.71 eV), a similar deep LUMO level, (−3.94 eV) and a higher HOMO level (−5.18 eV). Therefore, when Au metal was used as the electrode and the devices were tested under similar vacuum conditions, PBIBDF-BT exhibited n-type transport, whereas PBTPBF-BT exhibited ambipolar transport due to the deep LUMO and suitable HOMO levels. Highest mobilities of 0.45 and 0.22 cm2 V−1 s−1 were obtained for hole and electron, respectively. Under the air condition, the hole mobility of PBTPBF-BT significantly increased to 0.61 cm2 V−1 s−1 and electron mobility was maintained at 0.07 cm2 V−1 s−1. Overall, this study demonstrates that replacing the outer benzene with thiophene can effectively vary the polymer properties such as bandgap, energy levels and, as a result, tune the transport behavior.

The reflection bandwidth of cholesteric liquid crystals is typically on the order of 50–100 nm in the visible region. Static bandwidths greater than 100 nm can be observed in polymer stabilized cholesteric liquid crystals (PSCLCs) that possess a pitch gradient throughout the thickness of the cell. This work presents PSCLCs based on ionic polymer networks and chiral ions, which exhibit large reflection bandwidth tunability under a small applied direct current (DC) electric field. The reflection colors dynamically switch between white, orange, red and transparent. The underlying mechanism of the electrically controllable bandwidth in PSCLCs is the redistribution of the chiral ions under DC electric fields resulting in a pitch gradient variation along the optical axis. Removal of the electric field returns the PSCLC to its original optical properties due to the strong electronic attraction between the ionic polymer network and chiral ions. Moreover, the reflection bandwidth is also sensitive to the temperature.

A novel luminescent liquid crystal, (2Z,2′Z)-2,2′-(1,4-phenylene)bis(3-(4-(dodecyloxy)phenyl)acrylonitrile) (PDPA), is reported, which shows green, yellow and orange colors depending on the self-assembled structure. The luminescence of PDPA can vary between those three different colors invoked by mechanical shearing and thermal annealing. Moreover, an excellent liquid crystal phase transition of PDPA is observed using polarized optical microscopy (POM) and differential scanning calorimetry (DSC) analysis. Finally, a prototype device is fabricated that demonstrates rewritable fluorescence optical recording with multistimuli luminescence tuning.

A novel α-cyanostilbenic derivative, (Z)-2-(4-aminophenyl)-3-(4-(dodecyloxy)phenyl) acrylonitrile, is reported, wherein a Z–E isomerization process is accompanied by a remarkable decrease in compatibility with liquid crystals. Accordingly, fluorescent-molecule-dispersed liquid crystals have been prepared through a photoisomerization-induced phase separation method. The photoluminescence can be repeatedly switched by an electric field. Modulating the excitation light offers a new technique to explore electrically controllable photoluminescence.

A novel cyanostilbene derivative (I) is synthesized and sufficiently characterized, which is also utilized as the initiator to prepare poly(e-caprolactone) (I-PCL) and poly(D,L-lactide) (I-PLA) via ring-opening polymerization (ROP). Notably, molecule I exhibits superior aggregation-induced enhanced emission (AIEE) behavior in the mixed solvent of THF and water. The bulky cyano groups are linked to vinylene moieties in molecule (I) generating intramolecular coplanarity and preventing π–π stacking, which leads to enhanced emission in the aggregated state. Crystallographic data of I confirm that the existence of multiple intermolecular interactions among adjacent molecules restricts intramolecular vibration and rotation. In addition, molecule I can self-organize into ordered microtubes in appropriate THF/water mixtures exhibiting significant optical waveguide properties. Furthermore, the polymers, I-PCL and I-PLA, also show AIEE behaviors since the single chromophore I is anchored on the polymer chains. As compared with the corresponding small molecule I, the target polymers possess not only preferable thermostabilities but also the property of easy fabrication. The luminogen aggregation of the initiator is well-realized and even enlarged after polymerization, due to the linkage of polymer chains. In the end, the polymer I-PLA has a great prospect in white light-emitting diode (LED) application, which emits daylight white light.

A bis(2-oxoindolin-3-ylidene)-benzodifuran-dione (BIBDF)-based low band gap polymer (PBIBDF-BT), containing a solubilizing alkyl chain bithiophene unit as a donor, has been synthesized. The polymer with a low-lying LUMO/HOMO energy level (-4.03/-5.55 eV) exhibits efficient ambipolar charge transport. The electron and hole mobilities are as high as 1.08 and 0.30 cm(2) V(-1) s(-1), respectively.

Semiconducting/insulating polymer blends are promising materials for use in organic thin film transistor (OTFT) applications. Here, vertically phase-separated poly(3-hexylthiophene) (P3HT)-top and poly(methyl methacrylate) (PMMA)-bottom blend films were developed for the facile fabrication of OTFTs with excellent electrical properties. The microstructures of the blend films could be adjusted simply by altering the film processing conditions, which impacted the electrical properties of the OTFTs based on the blend films. A decrease in the P3HT content of the blend film significantly reduced the interface roughness between the semiconductor (P3HT) and dielectric (PMMA) layers, which reduced charge trapping or scattering, thereby increasing the field-effect mobility. A higher solution concentration tended to increase the drying time during film deposition, which allowed the P3HT molecules to self-organize over a long period of time. This led to an increase in the ordering of the phase-separated P3HT film, which significantly improved the device performance. TFTs based on a P3HT/PMMA (1/39 w/w) film prepared from a 4 wt% blend solution showed the best field-effect performance with a saturated field-effect mobility of 0.022 cm2 V−1 s−1 and an Ion/Ioff current ratio of 2 × 105. The vertically stratified P3HT/PMMA films were also suitable for the fabrication of all-polymer TFT devices on flexible substrates.

Two new conjugated polymers based on benzodithiophene (BDT) and alkyl-benzotrithiophene (alkyl-BTT, P1), or acyl-benzotrithiophene (acyl-BTT, P2) were synthesized by a Stille cross-coupling reaction. The polymers were characterized by gel permeation chromatography (GPC), ultraviolet-visible (UV-vis) absorption as well as electrochemical cyclic voltammetry (CV) tests. Compared to the alkyl-BTT-based polymer (P1), the acyl-BTT-based polymer (P2) displayed a lower optical bandgap and a lower HOMO energy level. Polymer solar cells (PSCs) also confirmed that P2-based devices possessed better photovoltaic properties than those of P1-based devices. The optimized photovoltaic devices were fabricated with an active layer of a blend P2 and PC71BM using 2 vol% 1,8-diiodooctane (DIO) as a solvent additive, and a PCE of 4.20% was obtained, with a Voc as high as 0.96 V under AM 1.5G illumination at 100 mW cm−2 with a solar simulator.