Ruonan Ji

High performance colored selective absorbers for architecturally integrated solar applications

Architecturally integrated solar thermal technologies such as solar water heaters and solar thermoelectric generators (STEGs) rely on spectrally selective solar absorbers. These solar absorbers need to have simultaneous high solar absorptivity (α) and low thermal emissivity (e), which always makes them look dark blue or black and so blocks architectural integrated solar applications. A colorful appearance should be taken into account for integration into architectural applications. Herein, colored absorbers with a TiNxOy absorbing layer and a TiO2/Si3N4/SiO2 dielectric stack are elaborately designed and can be fabricated with only two targets, Ti and Si, by using reactive magnetron sputtering. Both the theoretical and experimental results show that the color can be tuned a huge amount, while keeping solar absorptivity higher than 95% and thermal emissivity lower than 5%. The highest absorptivity and energy efficiency (α/e) values are 97.6% and 27.2, respectively. These materials can also be fabricated onto thermoelectric generators to demonstrate the conversion of solar energy into electricity. The open circuit voltage dramatically increases from 171 mV to 523 mV (3.1 times) when using the absorbers. Additionally, the colored solar absorbers can be deposited onto most types of substrate, even flexible substrates. They can simultaneously satisfy the aesthetic requirements and excellent energy performance required for architecturally integrated solar thermal and thermoelectric applications, as well as applications in other fields.

Colorful solar selective absorber integrated with different colored units.

Solar selective absorbers are the core part for solar thermal technologies such as solar water heaters, concentrated solar power, solar thermoelectric generators and solar thermophotovoltaics. Colorful solar selective absorber can provide new freedom and flexibility beyond energy performance, which will lead to wider utilization of solar technologies. In this work, we present a monolithic integration of colored solar absorber array with different colors on a single substrate based on a multilayered structure of Cu/TiN(x)O(y)/TiO(2)/Si(3)N(4)/SiO(2). A colored solar absorber array with 16 color units is demonstrated experimentally by using combinatorial deposition technique via changing the thickness of SiO(2) layer. The solar absorptivity and thermal emissivity of all the color units is higher than 92% and lower than 5.5%, respectively. The colored solar selective absorber array can have colorful appearance and designable patterns while keeping high energy performance at the same time. It is a new candidate for a number of solar applications, especially for architecture integration and military camouflage.

Effect of body size and larval experience on mate preference in Helicoverpa armigera (Hübner) (Lep., Noctuidae)

Abstract:  We studied the mating selection in the cotton bollworm, Helicoverpa armigera (Hübner), in relation to body size and larval diet in the laboratory. When provided with an artificial diet at larval stage, weight, body and forewing length did not affect the probability of a male/female moth being selected for mating, but the abdominal width of selected female moths was significantly wider than that of non‐selected female moths. 30 female moths were dissected and number of eggs was counted after mating, and there was a correlation between the abdominal width and egg number. There was also significant difference of weight loss between selected and non‐selected male/female moths after the mating. The effect of operational sex ratio on mating latency and copulation duration were tested, and the result indicated that mating latency of male selection was significantly longer than that of female selection, but the difference of copulation duration was not significant. Cotton, corn and peanut plants were provided to larvae to test the effect of larval host plant experience on mate choice. When cotton‐ and peanut‐fed moth severed as potential partners, both female and male of cotton‐fed moths significantly preferred cotton‐ to peanut‐fed moths for mating. The possible reasons for mate preference based on larval host plant experience may account for host plants attributes on sex pheromone variation and sexual maturity. These findings may impact Bacillus thuringiensis resistance management.

Interference-aided spectrum-fitting method for accurate film thickness determination

A new approach was proposed to accurately determine the thickness of film, especially for ultra-thin film, through spectrum fitting with the assistance of interference layer. The determination limit can reach even less than 1 nm. Its accuracy is far better than traditional methods. This determination method is verified by experiments and the determination limit is at least 3.5 nm compared with the results of AFM. Furthermore, double-interference-aided spectra fitting method is proposed to reduce the requirements of determination instruments, which allow one to determine the film thickness with a low precision common spectrometer and largely lower the cost. It is a very high precision determination method for on-site and in-situ applications, especially for ultra-thin films.

Twisted split-ring chiral metamaterials for broadband circular dichroism

In this paper, a kind of twisted split-ring chiral metamaterials is proposed to obtain integratable broadband circle dichroism. With coupling among closely spaced twisted split-rings, a broadband circle dichroism is achieved owning to the combined effect of Bragg resonance and internal resonance.

Strong and broadband circular dichroism based on helix-like chiral metamaterials

In this paper, a helix-like chiral metamaterials, which can be realized with multiple electron beam lithography, has been proposed to achieve strong and broadband circular dichroism. A preferential transmission of right-handed polarized waves spanning over a wavelength range of above 5 μm is realized owning to the combined effects of internal and Bragg resonance.