For highly interested organolead perovskite based solar cells, the exciton and free carriers are the photoproducts in the working layers. In this study, we revealed their two forms of relations depending on heat-annealing condition. In non-annealed films and single crystal, they are in density-dependent dynamical balance (co-existing). For the sufficiently heat-annealed films, they present a significant emissive exciton-carrier collision (ECC). The two relations indicate the emergence of a subgrain morphology within the tetragonal phase of crystal grain, induced by heat annealing process. Such subgrain structure could be assigned to a ferroelastic twinning structure recently found inside the crystal grain of the films. Since the heat annealing is a general procedure in preparing perovskite working layers, we propose that the ECC and subgrain morphology widely exist in real devices. We suggest that the subgrain structure provides another level of morphological basis for in depth understanding high performance of organolead perovskite working layers.
In this work, the high-frequency response of the Salisbury screen made of metallic thin film was investigated. The formulas of reflectivity and bandwidth coefficient were derived. Theoretical and numerical studies show that the spectrum of reflectivity presents a resonance type, which is symmetric to the resonance frequency. The reflectivity is determined only by the normalized surface resistance α of the metallic film at resonance, and by both α and wave impedance η2 of the isolation layer at other frequencies. For the bandwidth coefficient Δ, it is determined by the examined reflectivity Γa, η2 and α. Bandwidth coefficient can be improved by changing the wave impedance η2, and tuning the surface resistance to the optimum value αc which is correlated to Γa and not equal to the one in most cases. It is also noted that the thickness of the metallic thin film should be in the order of sub-micron or nanometers.
Genetic Algarilhm (GA) has been successfully used in lhe design of the radar absorbing materials with multi-layer configurations. A newly developed Multi-Zone Scheme (MZS) can bring us a better absorbing performance than &e Multi-Layer Scheme (MLS) does.Good agreement between expected result$ and physical measurement indicate that this method is powerful and promising. Comparisons between these two schemes are presented in this article and some examples are given to verify the effectiveness of MZS.
This article presents the configuration and performances of a kind of waterproof pyramidal microwave absorber for out-door using, analyzes the influence of glass fiber reinforced plastic cover on absorbing properties. The successful development of this product provide assurance and convenient for those firms where out-door measurements for antennas or other equipment are needed.
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