【作者】 王朝晔；

【导师】 徐骏；

【作者基本信息】 南京大学 ， 微电子学与固体电子学， 2020， 硕士

【摘要】 充分而高效地利用太阳能一直是人们孜孜以求的目标,特别是对于我国而言更为重要。在众多利用太阳能的途径中,太阳能热光伏系统由于其潜在的高效利用前景引起了人们极大的关注。其核心是对太阳光谱进行高效的调控,而针对底电池设计适当波长的发射体与滤波器是提升系统性能的关键之一。本文从选择性发射体和窄带滤波器对光谱的调控入手,对二维硅基光子晶体、硅基F-P腔滤波器的光谱调控性质进行了研究讨论,主要内容和结果如下:1.从耦合模理论的角度讨论了二维光子晶体对光谱的调控效应,利用FDTD Solution软件对不同结构的发射谱进行模拟仿真,对具有圆柱孔阵列的二维钨光子晶体的发射特性进行讨论。得出了圆柱孔结构参数对二维钨光子晶体的发射特性的影响:圆柱孔的半径与截止波长正相关,圆柱孔的深度越深、周期越小,发射谱的高发射部分的平均发射率越高。根据从二维钨光子晶体得出的结论,我们设计了硅基钨光子晶体选择性发射体,结构是在硅衬底上刻出圆柱孔阵列,并在孔的内壁增加一定厚度的金属钨涂层,其在模拟中具有优秀的选择性发射的特性,并且能很好地结合先进硅基微电子加工工艺,有望广泛地应用于硅基太阳能热光伏系统中。当温度为1458 K时,上述硅基钨光子晶体模拟得到的辐射谱在1.5μm 22.1μm波长范围内具有高能量密度,在波长小于1.5μm和大于2.1μm的范围内具有低能量密度。2.从干涉理论的角度讨论了多层膜F-P腔滤波器的工作机制,利用FDTD Solution软件对结构的透射谱进行模拟仿真,讨论了由不同折射率材料交替构成的DBR的层数和交替排列的顺序对透射谱的影响。由模拟结果看出高折射率材料放在的最外层可以使DBR层的反射率更高,相比于在最外层多一层低折射率材料的结构,这样的结构不仅可以得到品质因子更高的透射峰,还能减少材料吸收带来的影响。通过平衡工艺难度与性能提升,我们选用具有2.5个DBR周期的微腔。通过改变微腔的厚度,实现了透射峰波长的可调谐,分别在在1.1μm、1.5μm和2.0μm处得到了性能良好的透射峰。3.在PECVD系统中制备了a-SiN_x/a-SiN_yO_z微腔结构。首先讨论了不同实验参数生长得到的a-SiN_x/a-SiN_yO_z材料的折射率和元素构成等性质,选择了折射率分别为2.67和1.62的a-SiN_0.4和a-SiN_0.5O_1.7作为组成微腔的两种材料。利用微腔结构实现了对a-SiN_0.5O_1.7发光光谱的模式选择,证实了结构的调控作用,进而针对太阳能热光伏系统的应用,设计了中心波长为1.1μm和2μm的滤波器。在实验中得到了1.11μm波长处的透射峰,峰值为81%,半宽全高为76 nm;以及1.98μm波长处77%的透射率,半宽全高为130 nm。模拟和实验得到的透射谱吻合较好,但并不完全重合,最后我们从材料的消光系数、膜层之间的界面粗糙度、材料的折射率偏差以及实验中的各种误差分析了造成这种差异的原因,为进一步优化提供思路。更多还原

【Abstract】 Efficient use of solar energy has always been the goal of people’s diligence,especially for China.Among the many ways to use solar energy,solar thermophotovoltaic systems have attracted great attention because of their potential for efficient use.The core of STPV is to efficiently regulate the solar spectrum,and designing a selective emitter and a filter of appropriate wavelength for the bottom battery is one of the keys to improving system performance.In this paper,the spectral modulation properties of two-dimensional silicon-based photonic crystals and silicon-based F-P cavity filters are studied and discussed.The main contents and results are as follows:1.From the perspective of coupling mode theory,the regulatory effect of two-dimensional photonic crystals on the spectrum is discussed.The emission characteristics of two-dimensional tungsten photonic crystals with cylindrical hole array are discussed by using FDTD Solution software to simulate the emission spectrum of different structures.The influence of cylindrical hole structure parameters on the emission characteristics of two-dimensional tungsten photon crystals is obtained:the radius of cylindrical hole is positively correlated with the cut-off wavelength,the deeper the cylindrical hole and the smaller the cycle,the higher the average emission rate of the high emission part of the emission spectrum.Based on the conclusions drawn from two-dimensional tungsten photon crystals,we designed a silicon-based photon crystal selective emitter coated with tungsten.The structure is a cylindrical hole array carved on the silicon substrate and a metal layer of tungsten coating with a certain thickness is added to the inner wall of the hole.It has excellent selective emission characteristics in simulation,and can well combine advanced silicon-based microelectronic processing technology,which is expected to be widely used in silicon-based thermal photovoltaic systems.At a temperature of 1458 K,the radiation spectrum simulated by the above-mentioned silicon-based photonic crystals has a high energy density in the wavelength range of 1.5 to 2.1μm,and a low energy density in the range of less than 1.5μm and greater than 2.1μm.2.From the perspective of interference theory,the working mechanism of multi-layer F-P cavity filter is discussed.By using FDTD Solution software,the transmission spectrum of the structure is simulated,and the influence of the number of layers and alternating order of DBR composed of different refractive index materials on the transmission spectrum is discussed.The simulation results reveal that the more cycles the DBR has,the smaller the half-width full height of the transmission peak,and the lower the average transmission rate of the cut-off area on both sides of the transmission peak.However,these changes become weaker and weaker as the number of cycles increases further.In addition,we also found that the outermost layer of high refractive index materials can make the DBR layer reflector higher,compared to the outermost layer of a lower refractive index material structure,such a structure can not only obtain a higher quality factor transmission peak,but also reduce the impact of material absorption.By balancing process difficulty and performance improvements,we eventually chose a microcavity with 2.5 DBR cycles.By changing the thickness of the microcavity,the transmissible transmission peak wavelength is achieved,with a well-performing transmission peak at 1.1μm,1.5μm,and 2.0μm,respectively.3.a-SiN_x/a-SiN_yO_z microcavity structure was prepared in PECVD system.Firstly,the refractive index and element composition of the a-SiN_x/a-SiN_yO_z material obtained by different experimental parameters are discussed,and the refractive index of a-SiN_0.4 and a-SiN_0.5O_1.7 are selected as two materials for the microcavity.The mode selection of a-SiN_0.5O_1.7 luminescent spectrum was realized by using microcavity structure,which confirmed the regulatory effect of the structure.In turn,a filter with a central wavelength of 1.1μm and 2μm was designed for the application of STPV system.In the experiment,the transmission peak at the wavelength of 1.11μm was obtained,with a peak of 81%and a half-width full height of 76 nm,as well as a transmission peak at the wavelength of 1.98μm,with a peak of 77%and a half-width full height of 130 nm.The transmission spectrum obtained by the simulation and experiment is well matched,but not exactly coincides.Finally,we analyze the causes of this difference from the extinction coefficient of the material,the interface roughness between the membrane layers,the deviation of the refractive index of the material and the various errors in the experiment.更多还原