| Perfect light absorber/reflector based on artificial subwavelength structure can manipulate and tailor spectrum purposefully and selectively, which has an extensive application prospect in new energy, sensor, spectrum detection, stray light prevention, photonic device and nanolocalized photo-thermal manipulation, et al. Therefore, it has been a new research hotspot in recent years. This thesis deals with spectrum tailor and manipulation from near ultraviolet to middle and far infrared(IR) waves based on nano-composite film materials and artificial subwavelength structure. The overall goal is to obtain perfect absorbing/reflecting materials for solar spectrum, visible spectrum and IR spectrum, respectively. The main research results we obtained are summarized as following.1. A high performance solar selective absorber has been designed and prepared, which enables access to manipulate and tailor solar spectrum and IR spectrum selectively. A new approach for depositing Ti NxOy films with only one reactive gas of O2 has been demonstrated by reactive mid-frequency magnetron sputtering from a Ti N target. The optical and electronic properties of Ti NxOy films are adjusted from metallic to dielectric continuously by increasing oxygen content. Based on the accurate control of optical properties, a Ti NxOy based high performance solar selective absorber has been demonstrated with the aid of mutilayer light trapping structure. Its solar absorbance is as high as 97.5% and thermal emissivity is 4.3%(100 ℃) with total thickness of 230 nm, which has been deposited on both flexible substrate and a 100×100 mm large glass substrate. The solar absorbance can maintain above 90% for a broad incident angle range from 0° to 65°. The temperature resistance of the absorber is also studied, showing that it can maintain long-time thermal stability in air when the temperature is not more than 400 ℃. It is available for tempering process when deposited on glass. To further enhance the solar absorbance, an amorphous carbonfilms was inserted into the multilayer absorber and hence more than 98% solar absorbance is obtained.2. High performance colored solar selective absorber and monolithic integrated colored solar selective absorbers array have been designed and prepared, which possess both the colorful appearance and high energy efficiency by manipulation the visible spectrum and whole solar spectrum. A colored absorbers structure with wide tunable color gamut has been proposed to maintain high energy efficiency comparable with the traditional black absorber, breaking the limits of the existing colored absorbers which can’t balance the energy performance with color appearance together. With the same structure and materials, the color appearance can be tuned in a huge wide range by changing the thicknesses of each layer, while keeping very high energy performance always. A variety of colored solar selective absorbers have been fabricated on several kinds of substrates, including flexible substrates. Both the designed and experimental results show that their color can be tuned in a huge gamut, while keeping solar absorptivity higher than 95% and thermal emissivity lower than 5%. They are also fabricated on thermoelectric generators to demonstrate the conversion of solar energy into electricity, making a contribution to the architectural integration of solar thermoelectric generators(STEGs). The open circuit voltage dramatically increases from 171 m V to 523 m V(3.1 times) with the absorber. A monolithic integration of colored solar absorbers array with different colors on a single substrate is first proposed based on a multilayered structure of Cu/Ti NxOy/Ti O2/Si3N4/Si O2. A colored solar absorber array with 16 color units is demonstrated experimently by using combinatorial deposition technique via changing the thickness of Si O2 layer, showing a pattern of mosaic. The novel monolithic integrated colored solar absorbers array can also maintain high energy efficiency at the same time, which can provide new freedom and flexibility, and will leads to wider usage of solar technology.3. Perfect absorber/reflector at visible frequencies has been designed and fabricated, which manipulate and tailor visible spectrum successfully. A Ti N-based refractoryplasmonic metamaterials is proposed to absorb the visible light perfectly with the help of anti-reflection films. The finite-difference time-domain(FDTD) and effective medium theory are employed to simulate and calculate the spectrum of the structure. Ti N-Al N(Ti Al N) nano-composite film with adjustable optical property is prepared by magnetron co-sputtering from Ti N and Al target and reactive magnetron sputtering from Ti Al target, respectively. Based on the Ti N-Al N nano-composite film, perfect absorber at visible frequencies with structure of Ti Al N/Ti O2/Si O2 has been fabricated on kinds of substrates, including metal, semiconductor, glass and flexible PET. It shows more than 99.5% average absorptivity in the whole visible region(380 nm-780 nm). We find that the structure is directly applicable to all kinds of opaque substrates without metallic bottom. What’s more, a perfect absorber with aperiodic Ti N-Si3N4 stacks is designed to absorb more than 99.996% visible light between 400-750 nm. The aperiodic stacks are suitable for all kinds of substrates, including opaque and transparency. The perfect absorber is employed in a fluorescence confocal microscopy to eliminate stray light, which improve the image quality dramatically. Furthermore, the perfect absorber is combined with one-dimensional photonic crystal to tailor the visible spectrum arbitrarily and an ultra-narrow band absorber has been designed as a sample.4. Perfect absorber/reflector at infrared wavelengths has been designed to manipulate and tailor IR spectrum. Ti N-Si3N4(Ti Si N) nano-composite film with adjustable optical property is prepared by magnetron co-sputtering from Ti N and Si target. Ti Si N/Si3N4/Si O2 three-layer and Ti Si N-I/Ti Si N-II/Ti O2/Si3N4/Si O2 five-layer structure are proposed as perfect absorber at 1.0-2.0 μm and 2.0-2.5 μm, respectively. The calculated results show that for both the two structures on opaque substrates, more than 99.5% average absorptivity has been achieved in their respective waveband with thickness of about 1/4 central wavelength. For transparent substrates, they can also obtain the same effect by increasing the thickness of Ti Si N. The near IR perfect absorber is combined with one-dimensional photonic crystal to tailor the near IR spectrum arbitrarily and anultra-narrow band absorber has been designed as a sample. Transition metals or their silicide nano particle embedded in dielectric matrix are designed to form nano-composite film. Substrate/nano-composite film/dielectric/nano-composite film/dielectric four-layer structure is proposed as perfect absorber at middle and far infrared. With this structure, more than 99.5% average absorptivity has been achieved at 3.0-10.0 μm and 10.0-30.0 μm with thickness of about 1/4 central wavelength, respectively. The middle and far IR perfect absorber is also combined with one-dimensional photonic crystal to tailor the IR spectrum arbitrarily and an ultra-narrow band absorber has been designed as a sample. |
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