Synthesis and Characterization of Solution-Processible Donor-Acceptor Electrochromic Conjugated Copolymers Based on Quinoxalino[2',3':9,10]phenanthro[4,5-abc]phenazine as the Acceptor Unit.

Donor-acceptor (D-A) type conjugated polymers are of high interest in the field of electrochromism. In this study, three novel conjugated copolymers (PBPE-1, PBPE-2 and PBPE-3) based on quinoxalino[2',3':9,10]phenanthro[4,5-abc]phenazine (A) as the acceptor unit and 4,8-bis((2-octyldodecyl)oxy)benzo[1,2-b:4,5-b']dithiophene (D1) and 3,3-didecyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (ProDOT-decyl2, D2) as the donor units with different donor-to-acceptor ratios were successfully synthesized through Stille coupling polymerization. The polymers were then characterized by cyclic voltammetry (CV), fourier transform infrared (FT-IR) spectoscopy, X-ray photoelectron spectroscopy (XPS), spectroelectrochemistry, thermogravimetry (TG), electrochromic switching and colorimetry. Optical band gap values were calculated as 1.99 eV, 2.02 eV and 2.03 eV, respectively. The three copolymers have good solubility, distinct redox peaks, wide absorption spectra, good thermal stabilities, bright color changes and significant electrochromic switching properties. Compared to the other two copolymers, the PBPE-3 film exhibited high coloration efficiency values of 513 cm2·C-1 at 504 nm and 475 cm2·C-1 at 1500 nm. The films have the advantage of exhibiting cathodic and anodic coloration.

Triazine-Based Conjugated Microporous Polymers With Different Linkage Units for Visible Light-Driven Hydrogen Evolution.

Conjugated microporous polymers (CMPs), as a kind of two-dimensional material, have attracted extensive attention due to their advantages in visible light-driven photocatalytic splitting of water for hydrogen evolution. However, improving the microstructure and electronic structure of the material to enhance their photocatalytic performance for hydrogen evolution remains a challenge. We designed and reported two analogous CMPs including CMP-1 and CMP-2 that contain triazine and dibenzothiophene-S,S-dioxide units, which were prepared by Pd-catalyzed Suzuki-Miyaura coupling reaction. The main difference of two CMPs is that the triazine units are connected to benzene unit (CMP-1) or thiophene unit (CMP-2). Both of the CMPs exhibit excellent light capture capability, and compared with CMP-2, CMP-1 has faster separation rates and lower recombination rates for the charge carriers (electron/hole), and then, a higher hydrogen evolution rate was obtained from water decomposition reaction. We find the H2 production rate of CMP-1 can be up to 9,698.53 µmol g-1h -1, which is about twice of that of CMP-2. This work suggests that molecular design is a potent method to optimize the photocatalytic performance toward hydrogen evolution of the CMPs.

Linear hybrid siloxane-based side chains for highly soluble isoindigo-based conjugated polymers.

Three isoindigo-based conjugated polymers modified with linear hybrid siloxane-based side chains were synthesized (PIID-Cm-Si7, m = 5-7). All polymers showed good solubilities in halogenated hydrocarbons, aromatic hydrocarbons, ethers, alkanes, and esters. The polymer films of PIID-C5-Si7, PIID-C6-Si7, and PIID-C7-Si7 achieved mobilities of 0.32, 0.82, and 1.58 cm2 V-1 s-1, respectively.

Flexible, Low-Voltage, and n-Type Infrared Organic Phototransistors with Enhanced Photosensitivity via Interface Trapping Effect.

Flexible and low-voltage near-infrared organic phototransistors (NIR OPTs) were prepared with a low-band gap donor-acceptor conjugated polymer as the semiconductor layer and n-octadecyl phosphonic acid modified anodic alumina (AlO x/ODPA) as the insulating layer. The phototransistors exhibit the typical n-type transistor characteristics at a voltage below 5 V. The photosensitivity of phototransistors can be enhanced by regulating the packing densities of the ODPA self-assembled monolayers and forming different trap states. The enhanced OPTs exhibit good photosensitivity to 808-980 nm NIR with the photocurrent/dark current ratio and photoresponsivity as high as 5 × 103 and 20 mA W-1, respectively, benefiting from the charge-trapping effect at the AlO x/ODPA interface. The OPTs also present a fast optical switching speed of 20/30 ms and an excellent mechanical flexibility. The outstanding performance of the NIR OPTs indicates that the development of wearable electronics is, indeed, possible.

Theoretical screening of novel alkyne bridged zinc porphyrins as sensitizer candidates for dye-sensitized solar cells.

Alkyne bridged porphyrin sensitizers have attracted great attention in the field of dye-sensitized solar cells (DSSCs) because of their excellent photo-to-electric conversion efficiencies, among which YD2 has reached 11% while YD2-o-C8 has reached 11.9% solely and 12.3% co-sensitized with other sensitizers. Design and screening of porphyrin sensitizer candidates with wider electronic absorption spectra to further improve the photo-to-electric conversion efficiencies of corresponding solar cells is still very important. Twenty novel alkyne bridged zinc porphyrin sensitizer candidates composed of the donors diarylamino-, tri-4-methylphenyl-, tri-hydroxyl- and tri-amino-substituted zinc porphyrins as well as the selected acceptors E, M, Q, R and S have been designed and calculated at the density functional B3LYP level. YD2 and YD2-o-C8 are also calculated at the same level for comparison. The result shows that the sensitizer candidates all have smaller HOMO-LUMO gaps as well as wider and red-shifted absorption bands than those of YD2 and YD2-o-C8. Most of the sensitizer candidates have appropriate HOMO and LUMO energy levels relative to the redox potential of the mediator and the TiO2 conduction band, showing that they are promising to provide comparable or even higher photo-to-electric conversion efficiencies than 11% of YD-2 or 11.9% of YD2-o-C8.