| 1. |
- Su, Wenyan, et al.
(författare)
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Nonconjugated Terpolymer Acceptors with Two Different Fused-Ring Electron-Deficient Building Blocks for Efficient All-Polymer Solar Cells
- 2021
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 13:5, s. 6442-6449
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Tidskriftsartikel (refereegranskat)abstract
- The ternary polymerization strategy of incorporating different donor and acceptor units forming terpolymers as photovoltaic materials has been proven advantageous in improving power conversion efficiencies (PCEs) of polymer solar cells (PSCs). Herein, a series of low band gap nonconjugated terpolymer acceptors based on two different fused-ring electron-deficient building blocks (IDIC16 and ITIC) with adjustable photoelectric properties were developed. As the third component, ITIC building blocks with a larger pi-conjugation structure, shorter solubilizing side chains, and red-shifted absorption spectrum were incorporated into an IDIC16-based nonconjugated copolymer acceptor PF1-TS4, which built up the terpolymers with two conjugated building blocks linked by flexible thioalkyl chain-thiophene segments. With the increasing ITIC content, terpolymers show gradually broadened absorption spectra and slightly down-shifted lowest unoccupied molecular orbital levels. The active layer based on terpolymer PF1-TS4-60 with a 60% ITIC unit presents more balanced hole and electron mobilities, higher photoluminescence quenching efficiency, and improved morphology compared to those based on PF1-TS4. In all-polymer solar cells (all-PSCs), PF1-TS4-60, matched with a wide band gap polymer donor PM6, achieved a similar open-circuit voltage (V-oc) of 0.99 V, a dramatically increased short-circuit current density (J(sc)) of 15.30 mA cm(-2), and fill factor (FF) of 61.4% compared to PF1-TS4 = 0.99 V, J(sc) = 11.21 mA cm(-2), and FF = 55.6%). As a result, the PF1-TS4-60-based all-PSCs achieved a PCE of 9.31%, which is similar to 50% higher than the PF1-TS4-based ones (6.17%). The results demonstrate a promising approach to develop high-performance nonconjugated terpolymer acceptors for efficient all-PSCs by means of ternary polymerization using two different A-D-A-structured fused-ring electron-deficient building blocks.
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| 2. |
- Wang, Wei, et al.
(författare)
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Entropy Study on the Enhanced Heat Transfer Mechanism of the Coupling of Detached and Spiral Vortex Fields in Spirally Corrugated Tubes
- 2021
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Ingår i: Heat Transfer Engineering. - : Informa UK Limited. - 0145-7632 .- 1521-0537. ; 42:17, s. 1417-1431
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Tidskriftsartikel (refereegranskat)abstract
- The present work numerically studied the enhanced heat transfer mechanism of the coupled fields of detached and spiral vortices in symmetrical and asymmetrical spirally corrugated tubes. The heat transfer and viscous dissipation were analyzed by evaluating the entropy combined with the flow patterns, and the global entropy generation rate was analyzed by considering the local Nusselt number and friction factor. The results indicated that, both the leeside and windward corrugation angles had obvious effects on the strength of detached vortex and spiral flow, and also the location of the vortex. The maximum values of the heat transfer entropy were located at the boundary layers, and the heat transfer entropy of the secondary flow region was more distinguished than in other parts of the main flow region. The maximum values of friction entropy generation were located at both the boundary layers and the core of detached vortex. The performance evaluation criterion (PEC) presents nearly the same values for the four cases, when the Reynolds number (Re) is less than 6,300. In addition, the PEC of symmetrical spirally corrugated tube with corrugation angle equal to 25° showed the best performance, when Re is greater than 6,300. To keep the PEC above 1, Re should not exceed 33,000.
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| 3. |
- Wang, Wei, et al.
(författare)
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Parameter study of laminar flow and heat transfer in an interrupted microchannel heat sink with ribs
- 2021
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Ingår i: Heat Transfer Research. - 1064-2285. ; 52:2, s. 13-27
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Tidskriftsartikel (refereegranskat)abstract
- The enhanced heat transfer mechanism and parameter optimization of an interrupted microchannel heat sink with rectangular ribs (IMCHS-R) was numerically studied for Reynolds number ranging from 100 to 900, using ANSYS Fluent. Interrupted microchannel heat sinks with different kinds of rectangular ribs having different width, length, and locations were compared with a straight microchannel and microchannel interrupted chambers. The results indicated that the heat transfer and flow resistance were mainly strengthened at the sudden converging area and narrow channels, and the secondary flow area did not show a positive effect on heat transfer. The IMCHS-R with W2/W1 = 0.3 and L2/L1 = 0.7 presented the best behavior from both PEC and Stot-ave at Re = 500–700. The heat transfer performance can be improved 2.0 times compared to the straight microchannel heat sink and the PEC can reach a value larger than 1.5. However, the rib location has a little effect on the enhanced heat transfer performances.
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