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Selective emitter (SE) technology significantly influences the passivation and contact properties of n-TOPCon solar cells. In this study, three mask layers (SiOx, SiNx, and SiOxNy) were employed to fabricate n-TOPCon solar cells with phosphorus (P)-SE structures on the rear side using a three-step method. Additionally, phosphosilicon glass (PSG) was used to prepare n-TOPCon solar cells with P-SE structure on the rear side using four-step method, and the comparative analysis of electrical properties were studied. The SiOx mask with a laser power of 20 W (O2 group) achieved the highest solar cell efficiency (Eff, 24.85%), The open-circuit voltage (Voc) is 2.4 mV higher than that of the H1 group, and the fill factor (FF) is 1.88% higher than that of the L1 group. Furthermore, the final Eff of solar cell is 0.17% higher than that of the L1 group and 0.20% higher than that of the H1 group. In contrast, using the four-step method and a laser power of 20 W (P2 group), a maximum Eff of 24.82% was achieved. Moreover, it exhibited an Voc, which is elevated by 3.2 mV compared to the H1 group, and FF increased by 1.49% compared to the L1 group. Furthermore, the overall Eff of the P2 group outperforms both the L1 and H1 groups by approximately 0.14% and 0.17%, respectively. In the four-step groups, the Eff of each laser condition group was improved compared with the L1 group and H1 group, The stability observed within the four-step method surpassed that of the three-step groups. However, in terms of full-scale electrical properties, the three-step method can achieve comparable results as those obtained from the four-step method. This research holds significant guiding implications for upgrading the n-TOPCon solar cell rear-side technology during mass production. [ABSTRACT FROM AUTHOR]

With the development of Location-Based Social Networks, successive Point Of Interest (POI) recommendation systems have become a hot spot in the field of recommendation systems. Successive POI recommendation systems suggest to users new and interesting places to visit. However, in real-life POI recommendation, there are often a small number of users facing a huge number of POIs. Traditional successive POI recommendation methods are not capable to deal with the large sparse datasets, as they only consider the simple relationship between users and POIs. They do not use the context information of users and POIs, which can enable better recommendation results. To utilize the context information, this paper proposes a novel successive POI recommendation method, SQPMF, which integrates user personal preferences, user social relationships and POI transition relationships into the system for accurate recommendation of the next POI. Our experimental evaluation using three real-life datasets, Gowalla, Foursquare and Brightkite, shows that our method SQPMF consistently outperforms all state-of-the-art methods in recommendation of successive POIs. Compared with other methods, SQPMF improves Precision, Recall and F1-score by an average of at least 6.1 % , 5.8 % and 5.7 % respectively on three publicly available datasets. [ABSTRACT FROM AUTHOR]

Communication industry has developed relying on technological advancement in microelectronics and large-scale integrated circuits. Modified polyimide (MPI) materials with low dielectric loss, relatively simple fabrication process, and cost-effectiveness have significant social and economic benefits. In this work, 6FAPB and 6FDA were used to polymerize fluorinated PI films by thermal imidization, and SiO2 was used to modify PI films for further obtaining low dielectric constant (ε)/loss (tanδ) and enhance mechanical properties. The values of dielectric constant (ε) and tan δ were 2.75 and 0.00491, respectively, under 10 GHz. Meanwhile, the elastic modulus of MPI films was enhanced by the SiO2 adding process, with a maximum tensile modulus of 2.42 GPa. The results indicate that low polarity Si–O–Si bonds lead to a decrease in overall polarity of PI films and lead to tan decrease. This work provides a simple method to increase mechanical properties and reduce the dielectric constant/loss (at 10 GHz high frequency) of PI film by introducing trifluoromethyl and SiO2. [ABSTRACT FROM AUTHOR]

Supercapacitors (SCs) based on carbon nanofibers (CNFS) are being paid much attention due to their fast charge–discharge rate, high power density, and excellent cyclic stability. Herein, a kind of preferred hydroxyl‐containing poly(amic acid) solution is first synthesized by using 2,2‐bis(3‐amino‐4‐hydroxyphenyl)hexafluoropropane and pyromellitic dianhydride as monomers, and electrospun to prepare nanofiber membranes. Then, thermal imidization, thermally rearranged treatment, and carbonization are employed to successfully fabricate the corresponding hydroxyl‐containing polyimide (HPI)‐CNFs. Next, the activated CNFS are obtained through a simple activation treatment with KOH. After optimizing the concentration of KOH solution, the self‐standing and binder‐free CNF electrode A–HPI–CNFs–1/3 exhibits a maximum specific surface area of 2058 m2 g−1 and pore volume of 1.04 cm3 g−1, leading to a high specific capacitance of 387.7 F g−1 at 0.5 A g−1 and rate capability of 70% at 10 A g−1. In addition, the assembled symmetrical SC device shows outstanding cycle stability performance after 50000 runs of charge–discharge with a specific capacitance retention of 99.93% at 1 A g−1. Finally, the SC demonstrates a specific power of 12.7 Wh kg−1 at a specific energy of 250.0 W kg−1, suggesting potential application prospects in the field of SCs. [ABSTRACT FROM AUTHOR]

Herein, a kind of carbon/carbon composite electrode is prepared using polyimide (PI)/3D sphere‐like polyimide composite films as precursors, followed by carbonization. 2,2‐bis(3‐amino‐4‐hydroxyphenyl)hexafluoropropane and 4,4'‐(hexafluoroisopropylidene)diphthalic anhydride are polymerized and thermally imidized to form the matrix, and 3D sphere‐like PI particles synthesized by the solvothermal process are introduced via the in situ polymerization method. The electrochemical behaviors of C/C composites are examined in relation to the loading of the 3D sphere‐like PI crystals and carbonization temperatures. The C/C composite PI/5%3D‐PI‐800 demonstrates a specific capacitance maximum of 322.7 F g−1 at 0.5 A g−1 due to synergistic effects between different types of PIs. The specific capacitance decreases to 214 F g−1 with a retention rate of 66.3% as the current density increases to 10 A g−1. Moreover, the symmetrical supercapacitor (SC) assembled by PI/5%3D‐PI‐800 shows a specific capacitance of 244.4 F g−1 at 0.5 A g−1, with a high energy density of 33.94 Wh kg−1 and a power density of 500 W kg−1. In addition, after 6 months of storage, the button SC is retested and still shows fantastic capacitance retention rate of above 99.5%. Thus, this work proposes a facile method to fabricate the C/C composite electrodes with outstanding electrochemical properties. [ABSTRACT FROM AUTHOR]

The effect of Mg addition on the microstructure and sacrificial anode protection performance of a hot-dip Al-5Zn-4Si-xMg coating was studied by scanning electron microscopy (SEM-EDS), an X-ray diffractometer, and an electrochemical workstation. The results showed that Al-Zn-Si alloy was composed of an Al-rich phase and a Zn-rich phase. The MgZn2 phase appears after Mg addition. When the addition of Mg increased to 0.15 wt.%, the Mg2Si phase began to appear in the alloy. The hot-dip Al-5Zn-4Si-xMg coating consisted of Si particles, an Al-rich phase and a Zn-rich phase. When the Mg content increased to 0.15 wt.%, the Mg2Si phase and Al + Zn + MgZn2 eutectoid phase began to appear in the coating. In the full immersion corrosion test of the hot-dip Al-5Zn-4Si-xMg coating, the order of corrosion resistance was 0.15% Mg coating > 0.2% Mg coating > 0.05% Mg coating > 0 Mg coating. In the corrosion process of the hot-dip Al-5Zn-4Si-0.15Mg coating, with the increase in immersion, the self-corrosion current of the coating decreased, and the sacrificial protection performance was the best. [ABSTRACT FROM AUTHOR]