Working safety and workloads of Chinese delivery riders: the role of work pressure.

Using a sample of 9133 food delivery riders from T, a Chinese food delivery platform, this study applies a binary probit model to analyse influences of food delivery riders' workloads on the incidence of occupational injuries using self-control theory. We have found that food delivery riders' quantity of weekly orders delivered has an inverted U-shaped correlation with occupational injuries and those who rely heavily on platform income have a lower risk of injuries than those who rely less on platform income. After handling the problems of endogenous and missing variables through an instrumental variable method and robustness test, the conclusion is still robust. Moreover, work pressure is a mediator for workload influence on occupational injuries, but the platform safety training is not a boundary condition, for possible lacking in contents of workload control. Individuals with the experience of occupational injuries are less willing to continue working as food delivery riders.

Highly Efficient and High Peak Transmittance Colorful Semitransparent Organic Solar Cells with Hybrid-Electrode-Mirror Microcavity Structure.

Microcavity is an efficient approach to manufacture colorful semitransparent organic solar cells (ST-OSCs) with high color purity by tailoring the transmission spectrum to narrow peaks. However, in this type of colorful semitransparent devices, high power conversion efficiency (PCE) and high peak transmittance are not yet simultaneously achieved. This paper proposes a new type of microcavity structure to achieve colorful ST-OSCs with both high PCE and high peak transmittance, in which a hybrid Au/Ag electrode is used as a mirror and WO3 is used as a spacer layer. First, it is demonstrated that the hybrid Au/Ag electrode mirror brings about an improvement of 7.7 and 5.5% for PCE and peak transmittance, respectively, when compared with those of the reference devices using the Ag electrode mirror. Specifically, the PCE of the optimized devices reaches the satisfactory value of over 9%, and the peak transmittance is over 25%. This value of PCE is the highest one reported so far for the microcavity-based ST-OSCs with the same peak transmittance. Second, it is demonstrated that the second-order resonance of the microcavity can be used to improve the color purity of green ST-OSCs by narrowing the transmission peak, and the combination of the second-order and third-order resonance can be used to construct colorful ST-OSCs with mixed colors. Thus, a novel approach is developed to tune the color of ST-OSCs, which is based on high-order resonance modes of the microcavity.

Control of the Nucleation Density of Molybdenum Disulfide in Large-Scale Synthesis Using Chemical Vapor Deposition.

Atmospheric pressure chemical vapor deposition (CVD) is presently a promising approach for preparing two-dimensional (2D) MoS2 crystals at high temperatures on SiO2/Si substrates. In this work, we propose an improved CVD method without hydrogen, which can increase formula flexibility by controlling the heating temperature of MoO3 powder and sulfur powder. The results show that the size and coverage of MoS2 domains vary largely, from discrete triangles to continuous film, on substrate. We find that the formation of MoS2 domains is dependent on the nucleation density of MoS2. Laminar flow theory is employed to elucidate the cause of the different shapes of MoS2 domains. The distribution of carrier gas speeds at the substrate surface leads to a change of nucleation density and a variation of domain morphology. Thus, nucleation density and domain morphology can be actively controlled by adjusting the carrier gas flow rate in the experimental system. These results are of significance for understanding the growth regulation of 2D MoS2 crystals.