We successfully synthesized a series of novel symmetrical solution processable small molecules (APPM, AAPM and ATPM) consisting of the electron-accepting moiety (2-pyran-4-ylidenemalononitrile) (PM) and the electron-donating moiety (triphenylamine) linked by different electron-donating moieties (phenothiazine, triphenylamine and thiophene) through a Suzuki coupling reaction. Differential scanning calorimetry (DSC) measurement indicates that APPM and AAPM shows relatively high glass-transition temperature of ca. 137 °C and 163 °C, while the melting point of ATPM is at ca. 164 °C. UV-vis absorption spectra show that the combination of the PM moiety with moieties with a gradually increased electron-donating ability results in an enhanced intramolecular charge transfer (ICT) transition, which leads to an extension of the absorption spectral range and a reduction of the band gap of the molecules. Both cyclic voltammetry measurement and theoretical calculations displayed that the highest occupied molecular orbital (HOMO) energy levels of the molecules could be fine-tuned by changing the electron-donating ability of the electron-donating moieties. The bulk heterojunction (BHJ) photovoltaic devices with a structure of ITO/PEDOT/PSS/small molecules/PCBM/LiF/Al were fabricated by using the small molecules as donors and (6,6)-phenyl C 61-butyric acid methyl ester (PCBM) as acceptor. Power conversion efficiencies (PCE) of 0.65%, 0.94% and 1.31% were achieved for the photovoltaic devices based on APPM/PCBM, AAPM/PCBM and ATPM/PCBM under simulated AM 1.5 illumination (100 mW cm-2), respectively. The open circuit voltage of 1.0 V obtained from the device based on ATPM/PCBM is one of the highest values for organic solar cells based on solution processable small molecules
A series of solution processable small molecules (4TPM, 6TPM, and 8TPM) were synthesized with 2-pyran-4-ylidenemalononitrile (PM) as the electron-accepting unit and oligothiophene with different numbers as the electron-donating unit. Differential scanning calorimetry (DSC) measurement indicated that melting point and crystal temperature of molecules increased with the increase of thiophene number. UV-vis absorption demonstrated that the combination of PM with oligothiophene resulted in an enhanced intramolecular charge transfer (ICT) transition, which led to an extension of the absorption of the molecules. Cyclic voltammetry investigation displayed that the highest occupied molecular orbital (HOMO) energy levels of the three molecules were relatively low, which promised good air stability and high open circuit voltage (V oc ) for photovoltaic application. Theoretical calculations revealed that the variation laws of HOMO and the lowest unoccupied molecular orbital (LUMO) energy levels are well consistent with cyclic voltammetry measurement. The bulk heterojunction (BHJ) photovoltaic devices with the structure of ITO/PEDOT-PSS/small molecules-PCBM/ LiF/Al were fabricated, with the three molecules as donor and (6,6)-phenyl-C 61 -butyric acid methyl ester (PCBM) as the acceptor. The device based on 6TPM/PCBM (30:70 w/w) successfully achieved a maximum power conversion efficiency (PCE) of 1.15% under the illumination of AM 1.5, 100 mW/cm 2 .
Purpose The purpose of this paper is to determine the effect of flash fire exposure on the mechanical properties of single-layer thermal protective clothing. Design/methodology/approach The full-scale flame manikin tests were performed to simulate flash fire exposure. Two typical fire-resistant fabrics were investigated. The manikin was divided into seven body parts and the specimens meeting the requirements of tensile and tear strength standards were sampled. Fabric thickness, mass per unit area, tensile strength and tear strength were measured and analyzed. Findings The results revealed the significant influence of heat flux on both of tensile and tear strength. However, the regression analysis indicated the low R2 of the liner models. When the tensile and tear strength retention were reorganized based on the body parts, both of the multiple linear regression models for tensile and tear strength showed higher R2 than the one-variable linear regressions. Furthermore, the R2 of the multiple linear regression model for tear strength retention was remarkably higher than that of the tensile strength. Practical implications The findings suggested that greater attention should be paid to the local part of human body and more factors such as the air gap should be considered in the future thermal aging of firefighters’ clothing studies. Originality/value The outcomes provided useful information to evaluate the mechanical properties of thermal protective clothing and predict its service life.
Purpose -The purpose of this paper is to provide the details of developments to research works in the distribution characteristics of the air gaps within firefighters' clothing and research methods to evaluate the effect of air gaps on the thermal protective performance of firefighters' clothing. Design/methodology/approach -In this paper, the distribution of air gaps within firefighters' clothing was first analyzed, and the air gaps characteristics were summarized as thickness, location, heterogeneity, orientation and dynamics. Then, the evaluation of the air gap on the thermal protective performance of fighters' clothing was reviewed for both experimental and numerical studies. Findings -The air gaps within clothing layers and between clothing and skin play an important role in determining the thermal protective performance of firefighters' protective clothing. It is obvious that research works on the effects of actual air gaps entrapped in firefighters' clothing on thermal protection are comparatively few in number, primarily focusing on static and uniform air gaps at the fabric level. Further studies should be conducted to define the characteristic of air gap, deepen the understand of mechanism of heat transfer and numerically simulate the 3D dynamic heat transfer in clothing to improve the evaluation of thermal protective performance provided by the firefighters' clothing. Practical implications -Air gaps within thermal protective clothing play a crucial role in the protective performance of clothing and provide an efficient way to provide fire-fighting occupational safety. To accurately characterize the distribution of air gaps in firefighters' clothing under high heat exposure, the paper will provide guidelines for clothing engineers to design clothing for fighters and optimize the clothing performance. Originality/value -This paper is offered as a concise reference for researchers' further research in the area of the effect of air gaps within firefighters' clothing under thermal exposure.
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