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A novel synthesis method for fabricating large area, uniform bulk-heterojunction films with electron donor and acceptor materials homogeneously distributed among each other forming a bicontinuous network morphology is reported.

Perovskite solar cells (PSCs) have attracted significant research interest due to the rapid rise in efficiency. However, a large efficiency gap still exists between laboratory-based small devices and industrial-oriented large-scale modules. One of the main reasons for the efficiency losses is the degraded quality and morphology of the deposited large-area films, which is closely associated with crystallization processes. In this review, we discuss the nucleation and crystallization processes in solution and vapor-based up-scaling deposition methods for large-area perovskite films. We review recent scientific achievements and technical developments that have been made in the field of large-area cells. We present the existing problems that limit the performance of large devices and extensively discuss the key influencing parameters from the perspective of nucleation and crystallization over large areas. This review highlights the importance of crystallization control in up-scaling fabrications and presents promising strategies towards large-area perovskite-based optoelectronic devices.

Stereoregular fused thiophenes (SFTs: especially thieno[3,2-b]thiophene (TT) and dithieo[3,2-b:2′,3′-d]thiophene (DTT)), as stable conjugated structures deriving from thiophene ring enlarge...

The electrochemical behavior of organic conjugated semiconductors and their bulk materials is a considerable and irreplaceable parameter to maintain their diverse electronic or optoelectronic applications. In this paper, a series of n-type symmetrical perylene diimide derivatives (PTCDIs) with substituents (3,4-ethylenedioxythiophene (EDOT), cyclohexane, acetic acid, or propionic acid) at located the nitrogens imide position were synthesized, and their solubility, optical features, thermal stability, as well as solution-phase interfacial self-assembly into one-dimensional (1D) nanofibers and related morphology were discussed in detail. Moreover, a simple but effective method, in situ deposition following in situ self-assembly, was developed to construct uniform electrodes over a large area coated with networked PTCDI nanofibers. Then the electrochemical properties of the PTCDI nanofibers were researched in comparison with their molecules. The excellent variability at molecular or nanoscale morphological level will provide an interesting insight into the research of PTCDIs in a wide range applications of organic electronics.

Four 3,4-ethylenedoxythiophene (EDOT) end-capped oligomers employing single bond, EDOT, thieno[3,2-b]thiophene (TT) and dithieno[3,4-b;3′,4′-d]thiophene (DTT) units as bridge cores were synthesized and their polymers have been grown electrochemically. To reveal the relationship of structure-performance, the physicochemical properties, energy gaps, micromorphology, and photoelectrochemical behaviors of the oligomers or their polymers were systematically studied. These oligomers with planar rigid structures exhibit gradually narrowed molecular band gaps benefiting from their extended molecular conjugative degrees. These polymers present high electrochromic performances such as the higher optical contrast (59.61%) and coloring efficiency (288.37 cm2 C−1), excellent stability and color persistence. As a result, increasing cofacial conjugation degrees via integration of TT or DTT into polymer backbone is an efficient method to encourage the intermolecular π-interaction, which brings broad and strong absorption and promote the carriers rapidly transport in polymer backbones to enhance the photoelectric performances. This study will provide promising electrochromic polymers for display applications.

In recent years, polyselenophene and its derivatives have been paid more attention due to their unique properties such as lower band gaps and redox potentials. However, the poor solubility and molecular rigidity of polyselenophene and its derivatives limit them to use in flexible optoelectronic devices. Therefore, in order to enrich the structures and properties, fully understand the structure-property relationship and further improve the electrochromic performances of polyselenophene and its derivatives, we synthesized its propyl-analogues as precursors, to electrosynthesize three conducting polymers, poly(3,4‑propylenedioxyselenophene) (PProDOS) and its alkyl-modified derivatives, poly(3,3′‑dimethyl‑3,4‑dihydro‑2H‑selenopheno[3,4‑b][1,4]dioxepine) (PProDOS-C1) and poly(3,3′‑dibutyl‑3,4‑dihydro‑2H‑selenopheno[3,4‑b][1,4]dioxepine) (PProDOS-C4). The electrochemical and spectroelectrochemical behaviors of PProDOS and PProDOS-Cn (n = 1, 4) were investigated in detail in an ionic liquid, 1‑butyl‑3‑methylimidazolium hexafluorophosphate (BmimPF6). Results showed that PProDOS-C1 and PProDOS-C4 exhibited superior electrochromic performances such as high optical contrast (62%) and excellent coloration efficiency (573 cm2 C−1). In addition, as the alkyl chains increased, the onset oxidation potentials of monomers and the optical band gaps of polymer films decreased and the electrochemical activity of polymers increase. These polymers supply varied electrochromic colors and have prospect in display application.

A heterocyclic oligomer, thieno[3,2-b]thiophene (TT) end-capped famous 3,4-ethylenedioxythiophene (EDOT) unit and their electrosynthesized polymer P(TT-EDOT-TT) have been facilely achieved. To in-depth understand the effects of structural modification on physico-chemical properties and electrochromic performances of monomers and/or polymers, the absorption spectroscopy, electrochemistry, micromorphology, and spectroelectrochemistry were systematically studied. In contrast to TT and EDOT, TT-EDOT-TT possessed extended π-conjugation and narrowed band gap in molecular level. Through carefully comparison with PTT, it has been found that the electrochromic performances of P(TT-EDOT-TT) film exhibited much higher optical contrast (69%, while 3% for PTT in the near-infrared region) and superior coloring efficiency (255.3 cm2 C−1, while 36.8 cm2 C−1 for PTT), and switching times (within 1 s, while more than 9 s for PTT). Notably, P(TT-EDOT-TT) film can achieve the mutual conversion between RGB primary colors (red–green–blue) under variable voltages, which hold quite promising for display applications.

Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) is a hotspot among current researched conducting polymers and its conductivity could be significantly enhanced by post-treatment with dimethyl sulphoxide (DMSO). In this work, five S and Se analogues of 3,4-ethylenedioxythiophene (EDOT) were synthesized, and chemically oxidative polymerized (COP) to obtain corresponding free-standing films of Poly(3,4-ethylenedioxythiophene)s:poly(4-styrenesulfonate) (PEDOTs:PSS). The effect of chalcogen substitution on the physicochemical properties and conductive performances of PEDOT:PSS film have been demonstrated. In contrast to the conductivities about 10−2–10−1 S cm−1 for PEDOT:PSS and poly(3,4-ethylenedioxyselenophene):poly(4-styrenesulfonate) (PEDOS:PSS), other PEDOTs:PSS films had the conductivities about 10−4–10−5 S cm−1. The conductive enhancement effect of DMSO second-doping is suitable for PEDOTs:PSS films except the all-sulfur analogs of PEDOT:PSS (PEDTT:PSS and PEDTS:PSS), and the critical role of the presence of the O atoms in the ethylene bridges and the S atom in the thiophene ring has been illustrated. This work may help understand the structure-performance relationship of PEDOT family and the further development of PEDOTs in areas where the PEDOT seems monotonous and the high conductivity is not necessary, such as antistatic coating, anticorrosive coating, multi-colored electrochromics and so on.

In the era of miniaturization researchers are looking for electrochromic materials that combine cost-effective production technology, environmental stability and high performance. It has already been demonstrated that conducting polymers are ideal candidates for electrochromic applications. Herein, Electrosynthesis of poly(N-methyl-3,4-dihydrothieno[3,4-b][1,4]oxazine) (PMDTO) and poly(N-ethyl-3,4-dihydrothieno[3,4-b][1,4]oxazine) (PEDTO) were performed in green microemulsions (H2O, EtOH (ethanol) and Mix (H2O/EtOH)) containing LiClO4 and poly(styrenesulfonic acid) (PSSH). The onset oxidation potentials (Eonset) of monomers in these microemulsions were lower than those in common organic electrolytes, but the addition of PSSH brought increased Eonset (ca. 0.15 V) versus direct electropolymerization in H2O/LiClO4 electrolyte. SEM images show that PMDTO and PEDTO films obtained in H2O/PSSH/LiClO4 present smooth, tight morphology. Spectroelectrochemistry results indicate that their electrochromic performance comparable with that in organic solvents, and significantly improved optical kinetic stability in H2O electrolyte was observed, for which films under 1000s optical switching with little optical degradation. Based on these results, it is apparent that those polymers and systems have potential in electrochemical applications such as electrochromic devices and supercapacitors.

The morphology of electrode material is generally critical to affecting their electrochemical performance. Here, a porous poplar flower-like PEDOT-MeOH/PEG/WS2 hybrid material is successfully prepared using a simply co-electrodeposition method. With the assistance of poly(ethylene glycol) (PEG), the chemically exfoliated WS2 nanosheets are doped into poly(hydroxymethyl-3,4-ethylenedioxythiophene) (PEDOT-MeOH) film. The formation of a porous poplar flower-like PEDOT-MeOH/PEG/WS2 composite is proved by scanning electron microscopy, transmission electron microscopy, infrared spectra, energy-dispersive X-ray spectrometry and X-ray photoelectron spectroscopy. The maximum capacitance of the composite reaches 461.5 mF cm−2, which is 1.6 times greater than that of PEDOT-MeOH/PEG film. As-fabricated PEDOT-MeOH/PEG/WS2 composite can keep 85.8% of the initial areal capacitance after 5000 cycles. Additionally, PEDOT-MeOH/PEG/WS2-based symmetrical supercapacitor presents a capacitive capacity of 62.7 mF cm−2 at 0.5 mA cm−2, specific energy of 8.72 × 103 μWh cm−2 at 2.62 × 105 μW cm−2, and capacitive retention of 83.3% after 5000 cycles with a 100% coulombic efficiency. The capacitance improvement of PEDOT-MeOH/PEG/WS2 composite is closely related to porous poplar flower-like structure as well as the cooperation-enhancing effect between PEDOT-MeOH and WS2. These results imply that PEDOT-MeOH/PEG/WS2 composite will have great potential application in the field of the energy storage.

Conducting polymers (CPs), poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films, have shown excellent applications in the field of flexible electronics. In most cases, conductivity-enhancement reagents, such as popular dimethyl sulfoxide (DMSO), ethylene glycol (EG) and polyethylene glycol (PEG) have been demonstrated as necessary additives. However, their effects on the self-healing performances of such films were still unknown. Here, effects of these reagents as well as inorganic concentrated sulfuric acid (H2SO4) on the water-induced mechanical and electronic (conductive and thermoelectric) self-healing properties of PEDOT:PSS films were studied and corresponding mechanisms were illustrated. Meanwhile, analogous poly(3,4-ethylenedioxyselenophene):poly(styrene sulfonate) (PEDOS:PSS) film was investigated as a contrast. Treatment by EG showed 98 % recovery of conductivity and significantly reduced crack width after healing, while H2SO4 post-treatment only improved the self-healing of mechanical properties but significantly weakened the electrical properties. PEG or DMSO treatment showed negative influence on the self-healing of PEDOTs:PSS films. Since flexible electronic applications of PEDOTs:PSS films are highly inseparable from various additives or post-treatment, this initial research will help to clarify and optimize the synergy between electronic and self-healing behaviors.

Perylene tetracarboxylic diimide (PDI) and its derivatives exhibit excellent thermal, chemical and optical stability, strong electron affinity, strong visible-light absorption and unique fluorescence on/off features. The combination of these features makes PDIs ideal molecular frameworks for development in a broad range of sensors for detecting environmental pollutants such as heavy metal ions (e.g., Cu2+, Cd2+, Hg2+, Pd2+, etc.), inorganic anions (e.g., F−, ClO4−, PO4−, etc.), as well as poisonous organic compounds such as nitriles, amines, nitroaromatics, benzene homologues, etc. In this review, we provide a comprehensive overview of the recent advance in research and development of PDI-based fluorescent sensors, as well as related colorimetric and multi-mode sensor systems, for environmental detection in aqueous, organic or mixed solutions. The molecular design of PDIs and structural optimization of the sensor system (regarding both sensitivity and selectivity) in response to varying analytes are discussed in detail. At the end, a perspective summary is provided covering both the key challenges and potential solutions for the future development of PDI-based optical sensors.