Manipulating the interlayer carrier diffusion and extraction process in organic-inorganic heterojunctions: from 2D to 3D structures

Interlayer carrier transfer at heterointerfaces plays a critical role in light to electricity conversion using organic and nanostructured materials. However, how interlayer carrier extraction at these interfaces is poorly understood, especially in organic-inorganic heterogeneous systems. Here, we provide a direct strategy for manipulating the interlayer carrier diffusion process, transfer rate and extraction efficiency in tetracene/MoS2 type-II band alignment heterostructure by constructing the 2D–3D organic-inorganic (O-I) system. As a result, the prolonged diffusion length (12.32 nm), enhanced electron transfer rate (9.53 × 109 s−1) and improved carrier extraction efficiency (60.9%) are obtained in the 2D O-I structure which may be due to the more sufficient charge transfer (CT) state generation. In addition, we have demonstrated that the interlayer carrier transfer behavior complied with the diffusion mechanism based on the one-dimensional diffusion model. The diffusion coefficients have varied from 0.0027 to 0.0036 cm2 s−1 as the organic layer changes from 3D to 2D structures. Apart from the relationship between the carrier injection and diffusion process, temperature-dependent time-resolved spectra measurement is used to reveal the trap-related recombination that may limit the interlayer carrier extraction. The controllable interlayer carrier transfer behavior enables O-I heterojunction to be optimized for optoelectronic applications.

Mass Transfer Behavior and Microstructure Evolution of Li4TiO4-Li2TiO3 Core-shell Breeding Ceramic Under Harsh Operating Conditions

The development of novel tritium breeding materials was urgently needed in order to continuously optimize the tritium breeding ratio (TBR) of thermonuclear fusion reactors. From this point of view, Li4TiO4-Li2TiO3 core-shell breeding materials with more reasonable structure and theoretical Li density of 0.464 g/cm3 were prepared in this work. Notably, the mass transfer experiment at 900 °C in 1% H2/Ar shows that the theoretical Li density of this core-shell material after heating for 30 days was significantly higher than that of other breeding materials, indicating that it can provide more stable and efficient TBR. Specifically, the Li mass loss of the sample after 30 days heating was 3.4%, resulting in a decrease of Li density to 0.415 g/cm3. The mechanism of Li mass loss in Li4TiO4-Li2TiO3 core-shell breeding materials was investigated in detail. Moreover, the samples did not crack or collapse during the long-term heating process, and always maintained a satisfactory crushing load, revealing that this core-shell breeding ceramic can be used for a long time under severe operating conditions.

On Dispersion and Multipath Effects in Harmonic Radar Imaging Applications

In harmonic radar applications, images produced using algorithms of conventional radar applications experience some defocusing effects of the electronic targets’ impulse responses. This is typically explained by the dispersive transfer functions of the targets. In addition, it was experimentally observed that objects with a linear transfer behavior do not contribute to the received signal of a harmonic radar measurement. However, some signal contributions based on a multipath propagation can overlay the desired signal, which leads to an undesired and unusual interference caused by the nonlinear character of the electronic targets. Here, motivated by the analysis of measured harmonic radar data, the effects of both phenomena are investigated by theoretical derivations and simulation studies. By analyzing measurement data, we show that the dispersion effects are caused by the target and not by the measurement system or the measurement geometry. To this end, a signal model is developed, with which it is possible to describe both effects, dispersion and multipath propagation. In addition, the discrepancy between classic radar imaging and harmonic radar is analyzed.