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New small molecules having modified acceptor strength and π-conjugation length and containing dicyanovinylene (DCV) and tricyanovinylene (TCV) as a strongly electron-accepting unit with indacenodithiophene, IDT(DCV)2, IDT(TCV)2, and IDTT(TCV)2, were synthesized and studied in terms of their applicability to polymer solar cells with PTB7-Th as an electron-donating polymer. Intriguingly, the blended films containing IDT(TCV)2 and IDTT(TCV)2 exhibited superior shelf life stabilities of more than 1000 h without any reduction in the initial power conversion efficiency. The low-lying lowest unoccupied molecular orbital energy levels and robust internal morphologies of small TCV-containing molecules could afford excellent shelf life stability.

An oscillating multi-mold simulator with embedded thermocouples was used to study the initial solidification of medium carbon steels and crystallization characteristics of the mold flux. Casting speed variations in the simulator from 0.7 m/min to 1.4 m/min at fixed oscillation frequency and stroke resulted in higher copper mold temperatures. Frequency modifications from 2.5 Hz to 5.0 Hz and stroke changes from 8.1 mm to 5.4 mm at fixed casting speeds also resulted in higher copper mold temperatures. Surface profile analysis of as-cast steel strips showed characteristic oscillation marks comparable to the narrow faces of the industrial cast slabs. The apparent effect of casting variables on the temperature and surface profiles during the solidification of the medium carbon steels could be correlated to the variations in the negative strip time and subsequent changes in the extent of mold flux infiltration. Back scattered scanning electron microscope analysis of the full length of the retrieved flux film after casting showed cuspidine crystallization ratio that increased from the upper to lower portion of the flux film. This dynamic crystallization and growth of the cuspidine phase increases as the flux is sustained at high temperatures for longer periods. Additional experiments with industrial fluxes designed for soft cooling of medium carbon steel grades showed comparable infiltration thickness of the flux, but the crystallization characteristics were significantly different, which could have a significant impact on the heat transfer rate and mechanism through the flux film.

An inverted water-cooled multi-mold continuous casting simulator was used to investigate initial solidification of low-carbon steels and crystallization of mold flux. Embedded mold thermocouples showed characteristic temperature profiles dependent on parameters including casting speed, oscillation frequency, and stroke. Higher maximum temperatures for thermocouples at higher casting speeds, higher frequencies, and lower stroke lengths were observed. The surface of the as-cast steel strips showed oscillation marks similar to those of industrially cast slabs and higher casting speeds resulted in shallower oscillation marks. The measured pitch agreed well with the theoretical pitch suggesting the multi-mold simulator to be a cost-effective alternative to pursue fundamental studies on initial solidification in the mold. Analysis of the mold flux taken between the copper mold and solidified steel shell showed highly dendritic uni-directional crystallization occurring within the flux film suggesting that the heat transfer direction is dominantly horizontal towards the water-cooled copper mold. In addition, the solidified flux located at the upper to lower part of the mold suggested morphological differences in the size and shape of the crystalline phases indicating that crystallization ratio can increase depending upon the retention in the mold and subsequently decrease radiative heat transfer as the flux traverses down the mold.

In this study, we establish a 3-D numerical analysis model to analyze the thermal behavior and to obtain the detailed heat transfer coefficient of a copper mold in a continuous casting system. This heat transfer coefficient changes according to variations in the mold geometry or cooling system. For increased flow speeds of the cooling water, the heat transfer coefficient also increases, but the rate of increase for the coefficient diminishes at higher flow speeds. As the thickness of the mold between the melt and the cooling water slots increases, the mold’s heat transfer coefficient decreases. However, the uniformity of the heat transfer coefficient improves with greater thickness. The effect of distance between cooling water slots on the mold’s heat transfer coefficient is also observed. Calculations show that greater distances between cooling water slots decrease the heat transfer coefficient.

New regular and random diketopyrrolopyrrole (DPP)-based terpolymers (i.e., Reg-PBDPPT and Ran-PBDPPT, respectively) bearing DPP as an electron deficient unit and 2,2'-bithiophene and (E)-1,2-di(thiophen-2-yl)ethene as electron donating units were designed and synthesized, and their performance in photovoltaic cells was investigated precisely. The absorption properties and highest occupied molecular orbital (HOMO) of Reg-PBDPPT were found to be different from those of Ran-PBDPPT. The results of grazing incidence X-ray diffraction experiments revealed that Ran-PBDPPT typically had a predominantly edge-on chain orientation on the substrate, whereas Reg-PBDPPT showed mixed chain orientation both in pristine and thermally annealed films. Although Reg-PBDPPT exhibited a lower degree of edge-on chain orientation on the substrate, the corresponding TFTs showed a high hole mobility of 0.42-0.96 cm(2) V(-1) s(-1) and maintained a high current on/off ratio (10(6)). A polymer solar cell (PSC) composed of Reg-PBDPPT and PC71BM exhibited power conversion efficiencies (PCE) of 5.24-5.45%, which were higher than those of the Ran-PBDPPT-based PSCs. The enhanced efficiency was supported by an increase in the short circuit current, which is strongly related to the unique internal crystalline morphology and pronounced nanophase segregation behavior in the blend films. These results obviously manifested that this synthetic strategy for regular conjugated terpolymers could be employed to control morphological properties to obtain high-performance PSCs.

Of all the processing stages for wafers, interior temperature distribution in thermal treatment furnaces has a great influence on wafer properties. Therefore, internal temperature distribution is a key factor for operating a furnace. However, it is practically impossible to directly measure temperatures within the furnace, and consequently the need for a reliable numerical model to analyze temperature distribution is becoming increasingly urgent. Exact modeling of the processing is very difficult because the structure of the furnace used for thermal treatment is very complex, with large numbers of Si wafers stacked within. Therefore, simplified modeling is necessary. The modeling strategy of the present study is to reduce the radiation calculation domain and simplify the model by replacing the wafer stack region with a single block. It is necessary to determine the vertical and horizontal effective thermal conductivities of the block to reflect radiation heat transfer between wafers. In this study, calculations were performed through numerical experimentation, using r k as the heat transfer coefficient in the direction of the radius, and v k for the vertical direction. Using these calculated property values, the temperature distribution within a 300mm thermal treatment furnace can be obtained.

In the continuous casting process, molten flux film locates between mold and solidified shell. The film has two important roles. One is lubrication of two solids. The other role is controlling heat transfer from the shell to the mold. The shape of the liquid flux film is one of the most important factors for the film to execute both roles properly. However, the number of the studies about the shape of the film has been rare and results are quite different from each other. In the present study, a new approach is applied to determine the shape of the film. This approach is based on the force valence between static pressure of molten steel and internal pressure of liquid flux film and solving heat and momentum equations in the flux film. The results of the present study well explained the experimental results of laboratory and field operations.