Semiconductor III-V photonic crystal (PC) laser is regarded as a promising ultra-compact light source with unique advantages of ultralow energy consumption and small footprint for the next generation of Si-based on-chip optical interconnects. However, the significant material dissimilarities between III-V materials and Si are the fundamental roadblock for conventional monolithic III-V-on-silicon integration technology. Here, we demonstrate ultrasmall III-V PC membrane lasers monolithically grown on CMOS-compatible on-axis Si (001) substrates by using III-V quantum dots. The optically pumped InAs/GaAs quantumdot PC lasers exhibit single-mode operation with an ultra-low threshold of~0.6 μW and a large spontaneous emission coupling efficiency up to 18% under continuous-wave condition at room temperature. This work establishes a new route to form the basis of future monolithic light sources for high-density optical interconnects in future large-scale silicon electronic and photonic integrated circuits.

Monolithic integration of efficient III-V light-emitting sources on planar on-axis Si (001) has been recognized as an enabling technology for realizing Si-based photonic integrated circuits (PICs). The field of microdisk lasers employing quantum dot (QD) materials is gaining significant momentum because it allows massive-scalable, streamlined fabrication of Si-based PICs to be made cost effectively. Here, we present InAs/GaAs QD microdisk lasers monolithically grown on on-axis Si (001) substrate with an ultra-low lasing threshold at room temperature under continuous-wave optical pumping. The lasing characteristics of microdisk lasers with small diameter (D) around 2 μm and subwavelength scale (D∼1.1 μm) are demonstrated, with a lasing threshold as low as ∼3 μW. The promising lasing characteristics of the microdisk lasers with ultra-low power consumption and small footprint represent a major advance towards large-scale, low-cost integration of laser sources on the Si platform.

White organic light‐emitting diode (WOLED) technology has attracted considerable attention because of its potential use as a next‐generation solid‐state lighting source. However, most of the reported WOLEDs that employ the combination of multi‐emissive materials to generate white emission may suffer from color instability, high material cost, and a complex fabrication procedure which can be diminished by the single‐emitter‐based WOLED. Herein, a color‐tunable material, tris(4‐(phenylethynyl)phenyl)amine (TPEPA), is reported, whose photoluminescence (PL) spectrum is altered by adjusting the thermal annealing temperature nearly encompassing the entire visible spectra. Density functional theory calculations and transmission electron microscopy results offer mechanistic understanding of the PL redshift resulting from thermally activated rotation of benzene rings and rotation of 4‐(phenylethynyl) phenyl)amine connected to the central nitrogen atom that lead to formation of ordered molecular packing which improves the π–π stacking degree and increases electronic coupling. Further, by precisely controlling the annealing time and temperature, a white‐light OLED is fabricated with the maximum external quantum efficiency of 3.4% with TPEPA as the only emissive molecule. As far as it is known, thus far, this is the best performance achieved for single small organic molecule based WOLED devices.

In this study, we introduced dC/dV analysis based on the capacitance-voltage (C-V) measurement of quantum dot light-emitting diodes (QLEDs), and discovered that some key device operating parameters (electrical and optical turn-on voltage, peak capacitance, maximum efficiency) can be directly related to the turning points and maximum/minimum of the dC/dV (versus voltage) curve. By the dC/dV study, the behaviours like low turn-on voltage, simultaneous electrical and optical turn-on process, and carrier accumulation during the device aging can be well explained. Moreover, we performed the C-V and dC/dV measurement of aged devices, and confirmed our dC/dV analysis is correct for them. Thus, our dC/dV analysis method can be applied universally for QLED devices. It provides an in-depth understanding of the carrier dynamics in QLEDs through simple C-V measurement.

Antimony (Sb) is a dangerous heavy metal (HM) that poses a serious threat to the health of plants, animals, and humans. Leaching from mining wastes and weathering of sulfide ores are the major ways of introducing Sb into our soils and aquatic environments. Crops grown on Sb-contaminated soils are a major reason of Sb entry into humans by eating Sb-contaminated foods. Sb toxicity in plants reduces seed germination and root and shoot growth, and causes substantial reduction in plant growth and final productions. Moreover, Sb also induces chlorosis, causes damage to the photosynthetic apparatus, reduces membrane stability and nutrient uptake, and increases oxidative stress by increasing reactive oxygen species, thereby reducing plant growth and development. The threats induced by Sb toxicity and Sb concentration in soils are increasing day by day, which would be a major risk to crop production and human health. Additionally, the lack of appropriate measures regarding the remediation of Sb-contaminated soils will further intensify the current situation. Therefore, future research must be aimed at devising appropriate measures to mitigate the hazardous impacts of Sb toxicity on plants, humans, and the environment and to prevent the entry of Sb into our ecosystem. We have also described the various strategies to remediate Sb-contaminated soils to prevent its entry into the human food chain. Additionally, we also identified the various research gaps that must be addressed in future research programs. We believe that this review will help readers to develop the appropriate measures to minimize the toxic effects of Sb and its entry into our ecosystem. This will ensure the proper food production on Sb-contaminated soils.

Unlike red and green quantum dot light-emitting diodes (QLEDs), it is not clear whether a blue QLED is an electron-dominated device. In this work, we identify that electron is over-injected in blue QLEDs by impedance spectroscopy. By analyzing the capacitance–voltage characteristics of the single-carrier devices, we find that the built-in voltage of the electron-only device is smaller than that of the hole-only device. Therefore, electron injection is more efficient than hole injection in blue QLEDs. To support our arguments, we employ a red QD as a fluorescent sensor to spatially investigate the exciton recombination zone of a blue QLED. Consequently, we observe that the exciton recombination zone of the blue QLED is close to the hole transport layer, and it shifts toward an electron transport layer with the increase in the applied bias. Our work provides a practical method for identifying the excess carrier in blue QLEDs, and it could be applied to other types of QLEDs.

A field survey was conducted to determine the pollution grade, sources, potential ecological risk, and health risk of soil potentially toxic elements (PTEs) in Xikuangshan Mine (XKS), the largest antimony (Sb) deposit in the world. A total of 106 topsoil samples were collected from 6 sites in XKS to measure the concentrations of PTEs Cr, Zn, Cd, Pb, As, Hg, and Sb. The results show that the average concentrations of these elements at all six sites were generally greater than their corresponding background values in Hunan province, especially Sb, Hg, and As. Correlation and principal component analyses suggested that Cd, Zn, Pb, Hg, and Sb were primarily released from mining and other industrial and human activities, while Cr and As were mainly impacted by the parent material from pedogenesis. A risk index analysis showed that, overall, sites were at very high ecological risk, and Sb is the highest ecological risk factor, followed by Cd and Hg. According to health risk assessment, oral ingestion is the main non-carcinogenic and carcinogenic risk exposure route. The higher potentially non-carcinogenic and carcinogenic risks happen to the local children who live in the vicinity of mining area. It revealed that the mining and smelting processes of XKS have negatively influenced the local people, therefore, we should pay increasing attention to this practical issue and take effective measures to protect the ecology of XKS.

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