P型微晶硅薄膜材料性能的研究

本文讨论了P型微晶硅薄膜性能随硅烷浓度(SC)的变化.采用X射线衍射仪(XRD),拉曼光谱仪和傅立叶变换红外吸收光谱仪(FTIR)对薄膜的结构进行了表征.随硅烷浓度的增加,微晶硅薄膜材料的生长速率和暗电导率(σd)逐渐增大,光学带隙逐渐降低.当硅烷浓度为2.0;时,硅基薄膜材料是以非晶硅为主并有散落的微晶硅颗粒的非晶硅结构.当硅烷浓度为1.5;时,硼的掺杂效率最大,同时可观察到硼抑制薄膜晶化的现象.     

柔性衬底微晶硅太阳电池量子效率的研究

通过对微晶硅太阳电池量子效率的测量,结合微区拉曼光谱和电学特性测试,讨论了本征层的硅烷浓度和等离子体辉光功率对太阳电池量子效率的影响.发现本征层硅烷浓度增加时,电池的长波响应变差,材料结构由微晶相演变成非晶相;等离子体辉光功率的增加造成了电池短波响应的变化.同时发现测量微晶硅太阳电池时使用掩膜板所得短路电流密度与量子效率积分获得的短路电流密度相差不大.将优化后的沉积参数应用于不锈钢柔性衬底的非晶硅/微晶硅叠层太阳电池,获得了9.28;(AM0,1353 W/m2)和11.26;(AM1.5,1000 W/m2)的光电转换效率.     

VHF-PECVD法制备氢化硅薄膜及单结电池

利用VHF-PECVD分解硅烷和氢气的混合气体来制备本征微晶硅薄膜.运用拉曼散射和X射线衍射研究了不同硅烷浓度对薄膜的影响.随着硅烷浓度的增加,沉积速率和光敏性增加而晶化率下降.将优化的本征材料应用到pin电池中,得到本征层厚度约为1μm的微晶电池,效率达5.87;.     

RF-PECVD制备微晶硅薄膜的X射线衍射研究

采用X射线衍射(XRD)技术连续扫描法和薄膜衍射法对RF-PECVD制备的微晶硅薄膜结构进行了研究.改变硅烷浓度和反应功率,控制薄膜的生长速率,已达到制备不同材料的目的.根据硅基薄膜的电学特性和XRD测试,随着反应功率的增加,硅基薄膜的生长速率不断提高,微晶硅薄膜的晶化程度不断增大.     

PECVD沉积参数对非晶硅向微晶硅薄膜转化的影响

采用等离子体增强化学气相沉积(PECVD)系统,以硅烷和氢气为反应气源,通过改变射频功率、硅烷浓度来制备氢化硅基薄膜材料.研究了沉积参数的变化对硅基薄膜材料微结构的影响.通过红外吸收谱、紫外可见光谱以及X射线衍射谱对样品材料进行表征.实验结果表明,随着射频功率的增加,薄膜中氢含量也相应地增大,而光学带隙表现出先增大后减小的规律.当硅烷浓度逐渐降低时,薄膜材料的光学带隙相应地降低,并从非晶硅薄膜逐渐向微晶硅薄膜材料转变,且薄膜材料在(111)方向的晶粒尺度达到了10.92 nm.实现了在高沉积压强、大射频功率、低硅烷浓度条件下可以有效优化改善硅基薄膜质量.     

衬底温度对微晶硅薄膜微结构的影响

采用等离子体化学气相沉积(RF-PECVD)技术,在不同衬底温度Ts下沉积了氢化微晶硅(μc-Si:H)薄膜,并深入研究了衬底温度对微晶硅薄膜微结构的影响.研究结果表明随着衬底温度的升高,表征μc-Si:H 薄膜微结构的晶化率和平均晶粒尺寸均呈现了相似的变化规律,其临界温度点随着硅烷浓度的增加向高温方向移动.该实验结果可通过"表面扩散模型"得到合理解释.     

高压13.56MHz PECVD法沉积器件质量级本征微晶硅材料

本文国内首次报道了采用高压RF-PECVD技术沉积本征微晶硅材料的结果.实验表明,增大等离子体激发功率和减小硅烷浓度都能够使薄膜材料由非晶硅逐渐向微晶硅转变,而结构上的改变使得电学特性也随之改变.通过工艺参数的优化和纯化器的使用,有效地控制了氧的掺杂,在较高的生长速度下得到了器件质量级的本征微晶硅材料.将实验得到的微晶硅作为太阳电池光吸收层,在没有ZnO背电极和没有优化窗口层材料以及p/i界面时,电池的效率达到5.22;,这进一步表明本征微晶硅材料的良好性能.     

热丝化学气相沉积微晶硅薄膜结构及性质研究

采用热丝化学气相沉积(HWCVD)技术,以钨丝作为热丝,在不同热丝温度和氢稀释度下,分别在玻璃和单晶硅片衬底上沉积微晶硅(μc-Si∶H)薄膜材料.对所制备的微晶硅薄膜材料使用XRD、傅里叶变换红外吸收光谱、透射谱等进行结构与性能的表征分析.结果表明,随着热丝温度升高,氢稀释度变大,薄膜呈现明显的(220)择优生长取向,晶粒尺寸逐渐增大,光学吸收边出现红移,光学带隙逐渐变小.通过优化沉积参数,在热丝温度为1577℃、氢稀释浓度为95.2;、衬底温度为350℃,沉积速率为0.6 nm/s和沉积气压8 Pa条件下,制备的微晶硅薄膜呈现出了(220)方向的高度择优生长取向,平均晶粒尺寸为146 nm,光学带隙约为1.5 eV,光电导率σ.为3.2×10-6Ω-1·cm-1,暗电导率σrd为8.6×10-7 Ω-1·cm-1,表明制备的材料是优质微晶硅薄膜材料.     

硅烷浓度对微晶硅太阳电池的影响

采用甚高频等离子化学气相沉积技术(VHF-PECVD)制备了系列p-i-n型微晶硅太阳电池,研究了电池有源层硅烷浓度的变化对电池性能的影响.结果发现:随着硅烷浓度的提高电池的短路电流密度先提高然后降低,转换效率与之有相同的变化趋势,而开路电压随硅烷浓度的提高而增加,这些变化来源于有源层材料结构的改变.电池的填充因子几乎不受硅烷浓度的影响,但受前电极的影响很大.不同系列电池转化效率的最高点虽然处于非晶到微晶的过渡区,但对应电池的晶化率不同.另外,研究结果也给出非晶/微晶过渡区随着辉光功率的提高和沉积气压的降低向高硅烷浓度方向转移.     

SiCl4浓度对微晶硅薄膜生长及光电特性的影响

研究了SiCl4浓度对等离子体增强化学气相沉积(PECVD)系统中以SiCl4/H2为反应气体的微晶硅薄膜生长及光电特性的影响.结果表明,微晶硅薄膜的沉积速率和晶化率均随SiCl4浓度的增加而增大,而晶粒平均尺寸在SiCl4浓度小于65;时呈增大趋势,在SiCl4浓度大于65;时呈减小趋势;此外,光照实验表明制备的微晶硅薄膜具有较稳定的微观结构,具有类稳恒光电导效应,且样品的电导率依赖于SiCl4浓度的变化.此外,还讨论了Cl基基团在微晶硅薄膜生长过程中所起的作用.     

P型微晶硅氧薄膜光电性能研究

本工作采用甚高频等离子体化学气相沉积(VHF-PECVD)技术制备了P型微晶硅氧窗口层薄膜,讨论了P型微晶硅氧的光电特性随硼烷掺杂率的变化.采用紫外-可见透射光谱,拉曼光谱,傅立叶变换红外吸收光谱(FTIR),暗电导测量对薄膜的光电特性进行了表征.结果表明,P型微晶硅氧材料均表现为微晶态,随着硼烷掺杂率增加,晶化程度逐步降低,暗电导率快速减小,光学带隙持续降低.该结果可归因于硼烷掺杂的增加抑制晶化使得非晶成分增多,有效掺杂率降低导致薄膜电导率下降,另一方面,对硅氧物相分离的阻碍作用导致薄膜带隙下降.硼烷掺杂率为0.4;样品的电导率高达0.158 S/cm且光学带隙为2.2 eV,兼具高透射性和良好电导率,可作为高效硅基太阳电池的窗口层.     

Remote plasma deposition of microcrystalline silicon thin-films: Film structure and the role of atomic hydrogen

Microcrystalline silicon films grown in an expanding thermal plasma, i.e. in the absence of ion bombardment, are found to be porous and rich in nano-sized voids. By carrying out an extensive investigation on the material quality of films deposited in the amorphous-to-microcrystalline transition regime, on the microcrystalline silicon growth development, and on the influence of the substrate temperature, it is concluded that the inferior material quality is related to the lack of a sufficient amount of amorphous silicon tissue. As possible cause for the insufficient amount of amorphous silicon tissue, the interaction of atomic hydrogen with amorphous silicon films has been studied in order to highlight a possible competition between film growth and H-induced etching of amorphous silicon, and between film growth and H-induced surface/film modification. The etch rates obtained are too low to compete with film growth. Furthermore, atomic H cannot be considered responsible for the poor quality of amorphous tissue present in the microcrystalline silicon films, as the H up-take mainly takes place in divacancies. These results suggest that ion bombardment may be a necessary condition to provide good quality microcrystalline silicon films.     

本征微晶硅薄膜和微晶硅电池的制备及其特性研究

本文对VHF-PECVD制备的本征微晶硅薄膜和电池进行了电学特性和结构特性方面的测试分析研究.电学测试结果给出制备薄膜的激活能为0.51eV,符合电池对材料的电学参数要求;拉曼散射谱测试结果计算得到样品的晶化率为63;;X射线衍射结果也证明材料晶化,同时(220)方向择优;首次在国内用VHF-PECVD方法制备出效率为5;的微晶硅电池(Jsc=21mA/cm2,Voc=0.46V,FF=51;,Area=0.253cm2).     

Properties of thin film silicon,prepared at high growth rate in a wide range of thicknesses

Preparation of thin film silicon at high growth rate is an important target for its application in solar cells. The properties of hydrogenated microcrystalline silicon, prepared with the help of PECVD multi-hole cathode in a high pressure and depletion regime in a wide range of thicknesses are described in detail. We illustrate the surprising result that we can prepare high growth rate microcrystalline silicon from 0.4 up to 30 μm thickness without great peel-off problems. The room temperature dark DC conductivity, as well as the crystallinity, increased up to 5 μm film thickness and then started to decrease again. These results are explained by the initial temperature profiling and a thickness-induced increase of the lateral inhomogeneity.     

微晶硅薄膜纵向不均匀性的Raman光谱和AFM研究

本文研究了采用VHF-PECVD技术制备的微晶硅薄膜的纵向均匀性.喇曼测试结果显示:微晶硅薄膜存在着生长方向的结构不均匀,随厚度的增加,材料的晶化率逐渐变大;不同衬底其非晶孵化点是不一样的,对于同一种衬底,绒度大相应的晶化率就大,对应着孵化层的厚度小;AFM测试结果明显的给出:材料的结构随厚度增加发生变化.     

Preparation of microcrystalline silicon solar cells on microcrystalline silicon carbide window layers grown with HWCVD at low temperature

N-type microcrystalline silicon carbide layers prepared by hot-wire chemical vapor deposition were used as window layers for microcrystalline silicon n–i–p solar cells. The microcrystalline silicon intrinsic and p-layers of the solar cells were prepared with plasma-enhanced chemical vapor deposition at a very high frequency. Amorphous silicon incubation layers were observed at the initial stages of the growth of the microcrystalline silicon intrinsic layer under conditions close to the transition from microcrystalline to amorphous silicon growth. ‘Seed layers’ were developed to improve the nucleation and growth of microcrystalline silicon on the microcrystalline silicon carbide layers. Raman scattering measurement demonstrates that an incorporation of a ‘seed layer’ can drastically increase the crystalline volume fraction of the total absorber layer. Accordingly, the solar cell performance is improved. The correlation between the cell performance and the structural property of the absorber layer is discussed. By optimizing the deposition process, a high short-circuit current density of 26.7 mA/cm² was achieved with an absorber layer thickness of 1 μm, which led to a cell efficiency of 9.2%.     

Microcrystalline silicon oxide (μc-SiOx:H) alloys: A versatile material for application in thin film silicon single and tandem junction solar cells

We report on the development and application of n-type hydrogenated microcrystalline silicon oxide (μc-SiO_x:H) alloys in single and tandem junction thin film silicon solar cells. Single junction microcrystalline silicon (μc-Si:H) solar cells are prepared in n-i-p deposition sequence where n-type μc-SiO_x:H films serve as window layers. In tandem solar cells, μc-SiO_x:H layers are placed between amorphous (a-Si:H) and μc-Si:H component cells, serving as an intermediate reflector. The requirements for μc-SiO_x:H layer depending on its application are discussed. Our results show that the optical, electrical and structural properties of μc-SiO_x:H can be conveniently tuned over a wide range to fulfil various requirements for applications in both types of cells. Additionally, the properties of μc-SiO_x:H layers appear to be substrate dependent, which should be taken into account when layers are utilized in cells. The advantages of low refractive index and high optical band gap allow to achieve high efficiencies of 9.2% and 12.6% for single junction and tandem solar cells, respectively.     

PECVD低温制备微晶硅薄膜的研究

实验采用等离子体增强化学气相沉积(PECVD)法在玻璃衬底上制备了微晶硅薄膜.研究了氢稀释比、衬底温度、射频功率等因素对薄膜晶化的影响,得出在一定范围内随着衬底温度的升高、射频功率和氢稀释比的增大,薄膜的晶化率得到提高;但进一步提高沉积温度、射频功率反而会使薄膜晶化效果变差,并对晶化硅薄膜低温生长的机理进行了初步的探讨.     

Modulated photoconductivity method for investigation of band gap states distribution in silicon-based thin films

It has been demonstrated that the well known modulated photocurrent technique can be modified to escape imperfect data in intrinsic parameters of amorphous and microcrystalline silicon films and to simplify measurements of the density of localized states distribution in the band gaps of these semiconductors. The information on the density-of-states distribution can be extracted from temperature dependence measurements of the constant and modulated components of the photoconductivity in the film illuminated by the light modulated with some selected frequencies. The modified method has been applied to microcrystalline hydrogenated silicon films with n- and p-type conduction. The study has demonstrated that the tail of the density-of-states distribution near the valence band of microcrystalline hydrogenated silicon is less steep than that near the conduction band.