Showing papers by "Shanlin Qiao published in 2019"

Pore Surface Engineering of Covalent Triazine Frameworks@MoS2 Electrocatalyst for the Hydrogen Evolution Reaction

Abstract: Electrochemical water splitting is an important strategy for the mass production of hydrogen. Development of synthesizable catalysts has always been one of the biggest obstacles to replace platinum-group catalysts. In this work, a high quality crystal polymer covalent triazine framework [CTF; Brunauer-Emmett-Teller (BET) surface area of 1562.6 m2 g-1 ] is synthesized and MoS2 nanoparticles are grown in situ into/onto the 1 D channel arrays or the external surface for electrocatalysis [hydrogen evolution reaction (HER)] . The state-of-the-art CTFs@MoS2 structure exhibits superior catalytic kinetics with an overpotential of 93 mV and Tafel slope of 43 mV dec-1 , which is improved over most other reported analogous catalysts. The inherent π-conjugated crystal channels in CTFs provides a multifunctional support for electron transmission and mass diffusion during the hydrogen evolution process. Catalytic kinetics analysis shows that the HER performance is closely correlated to the hierarchical pore parameters and aggregated thickness of MoS2 nanoparticles. This work provides an attractive and durable alternative to synthesize high activity and stable catalysts for HER.

Structural engineering of pyrrolo[3,4-: F] benzotriazole-5,7(2 H,6 H)-dione-based polymers for non-fullerene organic solar cells with an efficiency over 12%

Abstract: In this work, we have synthesized two wide band gap donor polymers based on benzo[1,2-b:4,5-b′]dithiophene (BDT) and pyrrolo[3,4-f]benzotriazole-5,7(2H,6H)-dione (TzBI), namely, PBDT-TzBI and PBDT-F-TzBI and studied their photovoltaic properties by blending them with ITIC as an acceptor. Polymer solar cell devices made from PBDT-TzBI:ITIC and PBDT-F-TzBI:ITIC exhibited power conversion efficiencies (PCEs) of 9.22% and 11.02% and while annealing at 160 °C, improved the device performances to 10.24% and 11.98%, respectively. Upon solvent annealing with diphenyl ether (DPE) (0.5%) and chlorobenzene (CB), the PCE of the PBDT-F-TzBI-based device increased to 12.12%. The introduction of the fluorinated benzodithiophene (BDT-F) moiety on the backbone of PBDT-F-TzBI improved the open circuit voltage, short circuit current and fill factor simultaneously. The high PCEs of the PBDT-F-TzBI:ITIC-based devices were supported by comparison and analysis of the optical and electronic properties, the charge carrier mobilities, exciton dissociation probabilities, and charge recombination behaviors of the devices.

Novel benzodithiophene unit with an alkylthiobiphenyl side chain for constructing high-efficiency polymer solar cells

Abstract: A novel BDT monomer with an alkylthiobiphenyl side chain named 4,8-bis(4′-((2-hexyldecyl)thio)-[1,1′-biphenyl]-4-yl)benzo[1,2-b:4,5-b′]dithiophene (BDTBPS) was designed and synthesized. The polymer named PBDTBPS–BDD was synthesized with BDTBPS and benzo[1,2-b:4,5-b′]dithiophene-4,8-dione (BDD). Solar cells were studied by blending the polymer PBDTBPS–BDD with both fullerene and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC). The optimized polymer solar cells showed a PCE of 8.40% and 9.76% for the PC71BM-based and ITIC-based solar cells, respectively. This research indicates that the novel monomer is a promising unit for constructing high-efficiency polymer solar cells.

Rational Design of Low Band Gap Polymers for Efficient Solar Cells with High Open-Circuit Voltage: The Profound Effect of Me and Cl Substituents with a Similar van Der Waals Radius.

Abstract: Generally, low band gap material-based photovoltaic devices have reduced open circuit voltage (VOC), and realizing the trade-off between the low band gap (Eg 0.9 V) could be critical to give efficient polymer solar cells, especially for high-performance semitransparent PSCs and tandem solar cells. Although lots of efforts have been made to address the issue, most results have not been gratifying. In this work, the polymer PTBTz-Cl based on the chlorination method and efficient thiazole-induced strategy was designed and synthesized, aiming at the deep HOMO energy level, and the enhanced backbone planarity caused by the weak noncovalent Cl···S interaction. In addition, the methyl-substituted polymer PTBTz-Me was constructed as the reference due to the similar van der Waals radius of the side chain (CH3: 0.20 nm vs Cl: 0.18 nm). Encouragingly, in comparison with that of PTBTz-2, the newly synthesized polymers exhibit the red-shifted absorption spectra ranging from 300 to 770 nm, with an obviously reduced Eg of ∼1.6 eV. However, the function of Cl and Me substituents is different. Compared to the polymer PTBTz-Me, PTBTz-Cl exhibits a lower HOMO value, stronger crystallinity, and more compact intramolecular interactions. Consequently, the polymer PTBTz-Cl exhibits excellent photovoltaic performance with a notable VOC of 0.94 V and a power conversion efficiency of 10.35%, which is ∼11% higher than the 9.12% efficiency based on PTBTz-Me, and is also one of the highest values among polymer/fullerene solar cells. Moreover, a smaller photo energy loss (Eloss) of 0.64 eV is achieved, which is rare among the current high-performance polymer systems.