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Various copper-related defects in the absorption layer have been a key factor impeding the enhancement of the efficiency of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. Alkali metal doping is considered to be a good strategy to ameliorate this problem. In this article, Rb-doped CZTSSe (RCZTSSe) thin films were synthesized using the sol–gel technique. The results show that the Rb atom could successfully enter into the CZTSSe lattice and replace the Cu atom. According to SEM results, a moderate amount of Rb doping aided in enhancing the growth of grains in CZTSSe thin films. It was proven that the RCZTSSe thin film had the densest surface morphology and the fewest holes when the doping content of Rb was 2%. In addition, Rb doping successfully inhibited the formation of CuZn defects and correlative defect clusters and promoted the electrical properties of RCZTSSe thin films. Finally, a remarkable power conversion efficiency of 7.32% was attained by the champion RCZTSSe device with a Rb content of 2%. Compared with that of un-doped CZTSSe, the efficiency improved by over 30%. This study offers new insights into the influence of alkali metal doping on suppressing copper-related defects and also presents a viable approach for improving the efficiency of CZTSSe devices. [ABSTRACT FROM AUTHOR] more...

Despite the rapid development of urban rail transit in China, there are still some problems in train operation, such as low efficiency and poor punctuality. To realize a proper allocation of passenger flows and increase train frequency, this paper has proposed an improved urban rail transit scheduling model and solved the model with an adaptive fruit fly optimization algorithm (AFOA). For the benefits of both passengers and operators, the shortest average waiting time of passengers and the least train frequency are chosen as the optimization objective, and train headway is taken as the decision variable in the proposed model. To obtain higher computational efficiency and accuracy, an adaptive dynamic step size is built in the conventional FOA. Moreover, the data of urban rail transit in Zhengzhou was simulated for case study. The comparison results reveal that the proposed AFOA exhibits faster convergence speed and preferable accuracy than the conventional FOA, particle swarm optimization, and bacterial foraging optimization algorithms. Due to these superiorities, the proposed AFOA is feasible and effective for optimizing the scheduling of urban rail transit. more...

Streptomyces sp. TOR3209 is a plant growth-promoting rhizobacterium for tomato (Solanum lycopersicum L.) plants. This work reports its role in alleviating cold stress in tomato plants. By comparison with the wilting untreated controls, plants receiving TOR3209 treatment grew well at the low temperature of 5°C. To better understand the molecular mechanism induced by TOR3209 under cold stress, RNA sequencing was conducted in both leaf and root tissues to screen the differentially expressed genes. Twenty-nine up-regulated genes at 5°C were classified into three functional groups, such as abscisic acid biosynthesis and stress-related metabolism in roots, and photosynthesis in leaves. The increased amounts of abscisic acid, cold stress metabolites, antioxidants in the roots and increased photosynthetic activities in the leaves were subsequently verified in the plants treated with TOR3209. Our data demonstrate that Streptomyces sp. TOR3209 plays an extra role in promoting cold tolerance of tomato plants by regulating the abscisic acid signalling pathway, stress-related metabolism and photosynthesis. [ABSTRACT FROM AUTHOR] more...

In recent years, Cu2ZnSnS4 (CZTS)-based thin-film solar cells have received extensive attention for the optimization of grain growth and the suppression of defects by cation replacement. In this work, we report for the first time the replacement of stannum (Sn) atoms with antimony (Sb) doped into the lattice by solution treatment. Cu2ZnSbxSn1–x(S, Se)4 (0 ≤ x ≤ 0.2) (CZTSSSe) thin films are synthesized on soda lime glass substrates by sol–gel and two-step annealing techniques. The Sb doping strategy and the structural, morphological, optical, and electrical properties of CZTSSSe films are described. According to SEM results, it was found that the CZTSSSe (x = 0) thin film is composed of nanoscale small grains, and the right amount of Sb doping encourages grain growth, allowing for the fabrication of dense CZTSSSe films with bigger grain sizes and fewer holes. When x = 0.10, the best outcomes were attained. Sb successfully replaces the Sn sites, which decreases the production of harmful defects associated with Sn and enhances the electrical properties of thin films to improve carrier mobility. The open circuit voltage (VOC) of the CZTSSSe (x = 0.10) device increased by 29 mV as compared to the pure Cu2ZnSn-(S, Se)4 (CZTSSe) device, and its power conversion efficiency (PCE) increased from 5.06 to 6.82%. These outcomes exhibit the potential of Sb in enhancing the PCE of CZTSSe-based devices. [ABSTRACT FROM AUTHOR] more...