氢化微晶硅锗薄膜的微结构及光电特性的研究与优化
发布时间：2018-07-29 20:25
【摘要】：硅基薄膜太阳电池由于低成本等潜在优势,日益引起人们的重视并得到了迅速的发展。叠层太阳电池可有效提高硅基薄膜电池的转换效率和稳定性,成为目前硅薄膜研究领域的热点问题。氢化微晶硅锗薄膜(μc-Si1-xGex：H)由于具有窄带隙、带隙可调、高吸收系数等优点,是叠层电池中底电池有源层材料的理想选择之一,有着广阔的应用前景。 但μc-Si1-xGcx:H薄膜中存在复杂的混合相结构(非晶相、晶相、晶界和空洞)及各种合金组态的化学键(Si-Si、Si-Ge、Ge-Ge和(Si(Ge)-Hn)n等),为薄膜结构的分析和性能的优化带来一定的困难。为了获得不同Ge含量下μc-Si1-xGex:H薄膜的微结构及结构与光电性能的关系,本论文采用RF-PECVD技术,从薄膜微结构的角度出发,对μc-Si1-xGex:H薄膜的电学特性和光吸收性质进行了系统研究。主要研究内容和成果如下： 首先,我们从Ge含量(0～100%)和晶化率(Si-Ge,Si-Ge,Ge-Ge)这两个结构参数出发,系统地研究了不同Ge含量下,μc-Si1-xGcx:H薄膜的微结构及其对薄膜电学性质的影响。研究发现： 1)Ge含量小于60%时,与Ge相关的成键(Si-Ge和Ge-Ge)较易处于非晶网格中,薄膜的晶化率取决于Si-Si键的有序程度(XSi-Si)和Ge含量。通过对不同条件下制备的微晶硅锗薄膜的测试分析发现,Ge含量以及薄膜的晶化率的变化对薄膜的微结构及电学性能的影响主要存在以下几种规律：i,Ge含量的增加引起Xs--si减小,薄膜的整体晶化率减小。此时,虽然薄膜中的Ge悬挂键增加,但致密性变好。暗电导率单调减小,光电导率先减小后增大,薄膜的光敏性存在一个极大值；ii,Ge含量不变,随晶化率的提高,薄膜的H含量减小,结构因子R增加,晶粒增大,暗电导率增加,光电导率先增加后减小,当XSi-Si处于45～60%时,薄膜的光敏性达到了最大值；iii,Xsi-Si固定时,随Ge含量的增加,光电导率下降,暗电导率增加,薄膜光敏性下降。此时,继续增加Ge含量(大于70%)时,光、暗电导率明显增大,薄膜丧失光敏性；iv,通过调节工艺条件(如减小电极间距),使Ge含量和XSi-Si同时增加。随着Ge含量和XSi-Si的增加,薄膜H含量减小,结构较致密,光敏性存在最大值。 2)Ge含量大于60%时,通过提高氢稀释率或减小气体总流量等方法,可增加Si-Ge和Ge-Ge在有序结构中的含量,薄膜的晶化率增加。此时,薄膜晶粒尺寸较大,H含量较小,空洞数量和悬挂键含量增加。随着Ge含量的增加,薄膜的光电导率下降,暗电导率增加,光敏性大幅下降。 其次,系统研究了制备参数对μc-Si1-xGex:H薄膜光吸收特性的影响,并结合高压高功率技术,使薄膜同时获得高吸收系数和较好的电学性质。确定了低Ge含量下(≤25%),器件质量级μC-Si1-xGex:H薄膜的结构及实验参数。我们发现：减小电极间距、增加衬底温度或提高氢稀释均可使微晶硅锗薄膜的光吸收系数单调增加；而在气体总流量、辉光功率和沉积气压系列中,随着Ge含量的增加,光吸收系数都是先增加后减小。在基本实验参数得到优化的基础上,引入高压高功率技术,Ge悬挂键的减少改善了薄膜的电学性能；同时,薄膜总的有序度增加,空洞减少,结构更致密,这些促使了光吸收系数的增加。Ge含量小于25%的器件质量级μc-Si1-xGex:H薄膜及Ge含量处在25--45%区间的光电性能较好的μC-Si1-xGex:H薄膜的典型特征如下：1)Ge含量小于25%的薄膜：材料的暗电导率在10--10-S.cm-1；光敏性在1000～1500；1000nm处的光吸收系数大于103cm-1；Si-Si晶化率为45-60%；H浓度在6-8%；XRD测试结果给出(220)择优取向；晶粒大小在15-20nm之间；结构因子R小于0.3；Ge-H优先因子大于0.5；2)25～45%Ge含量的薄膜：材料的暗电导在10-～10-6S·cm-1；光敏性在500～700；1000nm处的光吸收系数大于5×103cm-1；Si-Si晶化率40～55%；H浓度在5-7%；XRD测试结果给出(220)择优取向；晶粒大小在15-25nm之间；结构因子R小于0.45；Ge-H优先因子大于0.2。 最后,为了充分发挥高Ge含量μc-Si1-xGex:H薄膜在拓展光谱响应和提高长波光吸收系数方面的优势,我们采用H2和He为稀释气体,进一步优化了高锗含量(～40%)的μc-Si1-xGex:H薄膜的微结构,改善其电学性质,使其具有较好的光电性能。He在等离子体中,发生“潘宁电离效应”,为薄膜的生长提供了额外的动量和能量。He的掺入能够抑制高Ge含量薄膜生长过程中H与Si优先键合的问题,减少Ge悬挂键,增加薄膜生长表面反应基团的迁移能力,从而优化了薄膜的电学性能。存在优化的He/H2稀释比,获得光敏性为1300、光电性能较好的40%Ge含量的μc-Si1-xGex:H薄膜。
[Abstract]:Silicon based thin film solar cells have been attracting more and more attention and developed rapidly because of their low cost and other potential advantages. The laminated solar cells can effectively improve the conversion efficiency and stability of silicon based thin film batteries, which have become a hot issue in the field of silicon film research. The hydrogenated microcrystalline silicon germanium film (c-Si1-xGex:H) has narrow band because of its narrow band. Gap, adjustable bandgap, high absorption coefficient and other advantages, is one of the ideal choice of the active battery layer materials for stacked batteries, and has broad application prospects.
However, the complex phase structure (amorphous phase, crystal phase, grain boundary and cavity) and the chemical bonds of various alloy configurations (Si-Si, Si-Ge, Ge-Ge and (Si (Ge) -Hn) n are present in the c-Si1-xGcx:H thin films, which bring some difficulties to the analysis and optimization of the properties of the thin films. In this paper, the electrical properties and optical absorption properties of the thin film are systematically studied by RF-PECVD technology. The main research contents and results are as follows:
First, starting from the two structural parameters of Ge content (0 ~ 100%) and crystallization rate (Si-Ge, Si-Ge, Ge-Ge), the microstructures and the effects on the electrical properties of the thin films under the different Ge content are systematically studied.
1) when the content of Ge is less than 60%, the bonding (Si-Ge and Ge-Ge) related to Ge is more easily in the amorphous grid. The crystallization rate of the film depends on the order of the Si-Si bond (XSi-Si) and the content of Ge. The microstructure and electricity of the film are found by the test and analysis of the microcrystalline silicon germanium film prepared under different conditions. The change of the Ge content and the crystallization rate of the film on the film is microstructure and electrical. The main effects of the performance are as follows: I, the increase of the content of Ge causes Xs--si to decrease and the overall crystallization rate of the thin film decreases. At this time, although the Ge suspension bond in the film increases, the density becomes better, the dark conductivity decreases monotonously, the photoconductivity increases first, and the photosensitivity of thin films has a maximum value; II, Ge content is unchanged. With the increase of crystallization rate, the H content of the film decreases, the structure factor R increases, the grain size increases, the dark conductivity increases, the photoconductivity increases first and then decreases. When XSi-Si is 45 ~ 60%, the photosensitivity of the film reaches the maximum value. When III, Xsi-Si is fixed, the photoconductivity decreases, the dark conductivity increases and the film photosensitivity decreases with the increase of Ge content. When the content of Ge is increased (more than 70%), the light, the dark conductivity obviously increases and the film loses the photosensitivity. IV, by adjusting the technological conditions (such as reducing the electrode spacing), the content of Ge and the XSi-Si are increased simultaneously. With the increase of Ge content and XSi-Si, the content of H in the film decreases, the structure is more compact, and the photosensitivity has the maximum value.
2) when the content of Ge is greater than 60%, the content of Si-Ge and Ge-Ge in the ordered structure can be increased by increasing the hydrogen dilution rate or reducing the total gas flow rate. The crystallization rate of the film is increased. At this time, the size of the thin film is larger, the content of H is smaller, the number of holes and the content of the suspended key are increased. With the increase of Ge, the photoconductivity of the film decreases and the dark electricity is reduced. The conductivity increased and the photosensitivity decreased significantly.
Secondly, the influence of the preparation parameters on the optical absorption characteristics of the c-Si1-xGex:H thin film is systematically studied, and the high absorption coefficient and the better electrical properties are obtained at the same time with high voltage and high power technology. The structure and experimental parameters of the low Ge content (less than 25%), the quality level of the device and the experimental parameters are determined. We find that the electrode spacing is reduced. The absorption coefficient of the microcrystalline silicon germanium film increases monotonously by increasing the substrate temperature or increasing the hydrogen dilution, and in the total gas flow, the glow power and the deposition pressure series, with the increase of the Ge content, the optical absorption coefficient is increased first and then decreases. On the basis of the optimization of the basic experimental parameters, the high voltage high power technology is introduced, and the Ge suspension is introduced. The decrease of the bond bond improves the electrical properties of the film. At the same time, the overall order of the film is increased, the cavity is reduced, and the structure is more compact. These have prompted the optical absorption coefficient to increase the.Ge content less than 25% of the device mass grade mu c-Si1-xGex:H film and the typical characteristics of the Ge thin film with better photoelectric performance in the 25--45% interval. Below: 1) thin film with Ge content less than 25%: the dark conductivity of the material is 10--10-S.cm-1; the photosensitivity is 1000~1500; the optical absorption coefficient of 1000nm is greater than 103cm-1; Si-Si crystallization rate is 45-60%; H concentration is 6-8%; XRD test results give (220) preferred orientation; grain size is between 15-20nm; structural factor R is less than 0.3; Ge-H priority causes The thin film with the content of 0.5 and 2) is 25 ~ 45%Ge: the dark conductance of the material is 10- to 10-6S. Cm-1; the photosensitivity is 500~700; the optical absorption coefficient of the 1000nm is greater than 5 x 103cm-1; the Si-Si crystallization rate is 40 to 55%; the H concentration is 5-7%; the XRD test results give the preferred orientation; the grain size is between the 15-25nm and the structural factor R is less than 0.45. H priority factor is greater than 0.2.
Finally, in order to give full play to the advantages of the high Ge content of the thin film of the c-Si1-xGex:H film in expanding the spectral response and increasing the absorption coefficient of the long wave light, we use H2 and He as diluting gases to further optimize the microstructure of the high germanium content (~ 40%) of the Mu c-Si1-xGex:H thin film, improve its electrical properties, and make it have good photoelectric properties.He at the same time. The "Pan Ning ionization effect" occurs in the subbody, which provides additional momentum and energy.He for the growth of the thin film, which can inhibit the H and Si preferential bonding during the growth of high Ge content, reducing the Ge suspension key and increasing the migration ability of the surface reaction group of the film growth, thus optimizing the electrical properties of the film. There is an optimized H. The e/H2 dilution ratio was obtained with a photosensitivity of 1300 and a 40%Ge c-Si1-xGex:H film with good photoelectric properties.
【学位授予单位】：南开大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM914.4;TN304.1
本文编号：2153907
[Abstract]:Silicon based thin film solar cells have been attracting more and more attention and developed rapidly because of their low cost and other potential advantages. The laminated solar cells can effectively improve the conversion efficiency and stability of silicon based thin film batteries, which have become a hot issue in the field of silicon film research. The hydrogenated microcrystalline silicon germanium film (c-Si1-xGex:H) has narrow band because of its narrow band. Gap, adjustable bandgap, high absorption coefficient and other advantages, is one of the ideal choice of the active battery layer materials for stacked batteries, and has broad application prospects.
However, the complex phase structure (amorphous phase, crystal phase, grain boundary and cavity) and the chemical bonds of various alloy configurations (Si-Si, Si-Ge, Ge-Ge and (Si (Ge) -Hn) n are present in the c-Si1-xGcx:H thin films, which bring some difficulties to the analysis and optimization of the properties of the thin films. In this paper, the electrical properties and optical absorption properties of the thin film are systematically studied by RF-PECVD technology. The main research contents and results are as follows:
First, starting from the two structural parameters of Ge content (0 ~ 100%) and crystallization rate (Si-Ge, Si-Ge, Ge-Ge), the microstructures and the effects on the electrical properties of the thin films under the different Ge content are systematically studied.
1) when the content of Ge is less than 60%, the bonding (Si-Ge and Ge-Ge) related to Ge is more easily in the amorphous grid. The crystallization rate of the film depends on the order of the Si-Si bond (XSi-Si) and the content of Ge. The microstructure and electricity of the film are found by the test and analysis of the microcrystalline silicon germanium film prepared under different conditions. The change of the Ge content and the crystallization rate of the film on the film is microstructure and electrical. The main effects of the performance are as follows: I, the increase of the content of Ge causes Xs--si to decrease and the overall crystallization rate of the thin film decreases. At this time, although the Ge suspension bond in the film increases, the density becomes better, the dark conductivity decreases monotonously, the photoconductivity increases first, and the photosensitivity of thin films has a maximum value; II, Ge content is unchanged. With the increase of crystallization rate, the H content of the film decreases, the structure factor R increases, the grain size increases, the dark conductivity increases, the photoconductivity increases first and then decreases. When XSi-Si is 45 ~ 60%, the photosensitivity of the film reaches the maximum value. When III, Xsi-Si is fixed, the photoconductivity decreases, the dark conductivity increases and the film photosensitivity decreases with the increase of Ge content. When the content of Ge is increased (more than 70%), the light, the dark conductivity obviously increases and the film loses the photosensitivity. IV, by adjusting the technological conditions (such as reducing the electrode spacing), the content of Ge and the XSi-Si are increased simultaneously. With the increase of Ge content and XSi-Si, the content of H in the film decreases, the structure is more compact, and the photosensitivity has the maximum value.
2) when the content of Ge is greater than 60%, the content of Si-Ge and Ge-Ge in the ordered structure can be increased by increasing the hydrogen dilution rate or reducing the total gas flow rate. The crystallization rate of the film is increased. At this time, the size of the thin film is larger, the content of H is smaller, the number of holes and the content of the suspended key are increased. With the increase of Ge, the photoconductivity of the film decreases and the dark electricity is reduced. The conductivity increased and the photosensitivity decreased significantly.
Secondly, the influence of the preparation parameters on the optical absorption characteristics of the c-Si1-xGex:H thin film is systematically studied, and the high absorption coefficient and the better electrical properties are obtained at the same time with high voltage and high power technology. The structure and experimental parameters of the low Ge content (less than 25%), the quality level of the device and the experimental parameters are determined. We find that the electrode spacing is reduced. The absorption coefficient of the microcrystalline silicon germanium film increases monotonously by increasing the substrate temperature or increasing the hydrogen dilution, and in the total gas flow, the glow power and the deposition pressure series, with the increase of the Ge content, the optical absorption coefficient is increased first and then decreases. On the basis of the optimization of the basic experimental parameters, the high voltage high power technology is introduced, and the Ge suspension is introduced. The decrease of the bond bond improves the electrical properties of the film. At the same time, the overall order of the film is increased, the cavity is reduced, and the structure is more compact. These have prompted the optical absorption coefficient to increase the.Ge content less than 25% of the device mass grade mu c-Si1-xGex:H film and the typical characteristics of the Ge thin film with better photoelectric performance in the 25--45% interval. Below: 1) thin film with Ge content less than 25%: the dark conductivity of the material is 10--10-S.cm-1; the photosensitivity is 1000~1500; the optical absorption coefficient of 1000nm is greater than 103cm-1; Si-Si crystallization rate is 45-60%; H concentration is 6-8%; XRD test results give (220) preferred orientation; grain size is between 15-20nm; structural factor R is less than 0.3; Ge-H priority causes The thin film with the content of 0.5 and 2) is 25 ~ 45%Ge: the dark conductance of the material is 10- to 10-6S. Cm-1; the photosensitivity is 500~700; the optical absorption coefficient of the 1000nm is greater than 5 x 103cm-1; the Si-Si crystallization rate is 40 to 55%; the H concentration is 5-7%; the XRD test results give the preferred orientation; the grain size is between the 15-25nm and the structural factor R is less than 0.45. H priority factor is greater than 0.2.
Finally, in order to give full play to the advantages of the high Ge content of the thin film of the c-Si1-xGex:H film in expanding the spectral response and increasing the absorption coefficient of the long wave light, we use H2 and He as diluting gases to further optimize the microstructure of the high germanium content (~ 40%) of the Mu c-Si1-xGex:H thin film, improve its electrical properties, and make it have good photoelectric properties.He at the same time. The "Pan Ning ionization effect" occurs in the subbody, which provides additional momentum and energy.He for the growth of the thin film, which can inhibit the H and Si preferential bonding during the growth of high Ge content, reducing the Ge suspension key and increasing the migration ability of the surface reaction group of the film growth, thus optimizing the electrical properties of the film. There is an optimized H. The e/H2 dilution ratio was obtained with a photosensitivity of 1300 and a 40%Ge c-Si1-xGex:H film with good photoelectric properties.
【学位授予单位】：南开大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM914.4;TN304.1
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