Simulation and experimental study of a novel bifacial structure of silicon heterojunction solar cell for high efficiency and low cost

A novel structure of Ag grid/SiN_x/n~+-c-Si/n-c-Si/i-a-Si:H/p~+-a-Si:H/TCO/Ag grid was designed to increase the efficiency of bifacial amorphous/crystalline silicon-based solar cells and reduce the rear material consumption and production cost. The simulation results show that the new structure obtains higher efficiency compared with the typical bifacial amorphous/crystalline silicon-based solar cell because of an increase in the short-circuit current(J_(sc)), while retaining the advantages of a high open-circuit voltage, low temperature coefficient, and good weak-light performance. Moreover,real cells composed of the novel structure with dimensions of 75 mm × 75 mm were fabricated by a special fabrication recipe based on industrial processes. Without parameter optimization, the cell efficiency reached 21.1% with the J_(sc) of 41.7 mA/cm~2. In addition, the novel structure attained 28.55% potential conversion efficiency under an illumination of AM 1.5 G, 100 mW/cm~2. We conclude that the configuration of the Ag grid/SiN_x/n~+-c-Si/n-c-Si/i-a-Si:H/p~+-a-Si:H/TCO/Ag grid is a promising structure for high efficiency and low cost.     

采用纳米晶柱阵列衬底抑制失配位错形成的分子动力学模拟研究

运用分子动力学方法对纳米晶柱阵列衬底上铝簿膜的外延生长进行了模拟研究.所采用的原子间相互作用势为嵌入原子法(EAM)多体势.模拟结果表明：采用纳米晶柱阵列衬底可以在不形成失配位错的条件下释放其上生长的外延薄膜晶体中的失配应变,有效地抑制其中失配位错的形成,获得高质量的外延薄膜晶体;这种纳米晶柱阵列的几何设计应满足两个基本条件：1) 晶柱的横截面尺寸应大于对应温度下的晶柱热失稳临界尺寸,以克服纳米结构的热失稳,模拟显示700K下铝的热失稳临界尺寸为19nm;2) 晶柱的高度与间距之比应大于076,以保证 关键词： 失配位错 分子动力学 纳米晶柱 铝     

Photoemission cross section:A critical parameter in the impurity photovoltaic effect

A numerical study has been conducted to explore the role of photoemission cross sections in the impurity photovoltaic(IPV) effect for silicon solar cells doped with indium. The photovoltaic parameters(short-circuit current density, opencircuit voltage, and conversion efficiency) of the IPV solar cell were calculated as functions of variable electron and hole photoemission cross sections. The presented results show that the electron and hole photoemission cross sections play critical roles in the IPV effect. When the electron photoemission cross section is 10-20cm~2, the conversion efficiencyη of the IPV cell always has a negative gain(?η 0) if the IPV impurity is introduced. A large hole photoemission cross section can adversely impact IPV solar cell performance. The combination of a small hole photoemission cross section and a large electron photoemission cross section can achieve higher conversion efficiency for the IPV solar cell since a large electron photoemission cross section can enhance the necessary electron transition from the impurity level to the conduction band and a small hole photoemission cross section can reduce the needless sub-bandgap absorption. It is concluded that those impurities with small(large) hole photoemission cross section and large(small) electron photoemission cross section,whose energy levels are near the valence(or conduction) band edge, may be suitable for use in IPV solar cells. These results may help in judging whether or not an impurity is appropriate for use in IPV solar cells according to its electron and hole photoemission cross sections.     

外延生长薄膜中失配位错形成条件的分子动力学模拟研究

运用分子动力学方法对负失配条件下的外延铝簿膜中失配位错的形成进行了模拟研究.所采 用的原子间相互作用势为嵌入原子法(EAM)多体势.模拟结果显示：在500K下长时间静态弛豫 ，表面和内部结构完整的外延膜在9—80原子层厚度范围内(约为其热力学临界厚度的3—40 倍)均不形成失配位错，而在薄膜表面预置一个单原子层厚、三个原子直径大小的凸台或凹 坑时，失配位错则能够在15个原子层厚的外延膜上迅速形成：在动态沉积生长条件下，表面 自然形成凹凸，初始厚度为9个原子层厚的外延膜在沉积生长中迅速形成失配位错.在三种条 件下，所形成的位错均为伯格斯矢量与失配方向平行的全刃位错.分析发现：在压应力作用 下，表面微凸台诱发了其侧薄膜内部原子的挤出，造成位错形核；而表面微凹坑则直接因压 应力作用形成了一个表面半位错环核. 关键词： 外延薄膜 失配位错 分子动力学 铝     

β-FeSi2 as the bottom absorber of triple-junction thin-film solar cells: A numerical study

Using β-FeSi2 as the bottom absorber of triple-junction thin-film solar cells is investigated by a numerical method for widening the long-wave spectral response. The presented results show that the β-FeSi2 subcell can contribute 0.273 V of open-circuit voltage to the a-Si/μc-Si/β-FeSi2 triple-junction thin-film solar cell. The optimized absorber thicknesses for a- Si, μ-Si, and/3-FeSi2 subcells are 260 nm, 900 nm, and 40 nm, respectively. In addition, the temperature coefficient of the conversion efficiency of the a-Si/μc-Si//3-FeSi2 cell is -0.308 %/K, whose absolute value is only greater than that of the a-Si subcell. This result indicates that the a-Si/μc-Si/β-FeSi2 triple-junction solar cell has a good temperature coefficient. As a result, using β-FeSi2 as the bottom absorber can improve the thin-film solar cell performance, and the a-Si/μc-Si/β-FeSi2 triple-junction solar cell is a promising structure configuration for improving the solar cell efficiency.     

铅基卤化物钙钛矿太阳电池的模拟研究

多元硫化物Cd_0.5Zn_0.5S和氧化亚铜Cu₂O载流子迁移率较大,且其制作工艺相对于传统的电子传输层和空穴传输层更为简单,因此这两种材料在钙钛矿太阳电池中具有很好的应用潜力。本文利用SCAPS-1D软件对以Cu₂O和Cd_0.5Zn_0.5S为传输层、以铅基卤化物钙钛矿为吸收层的太阳电池进行模拟,主要研究了该器件的材料厚度、掺杂浓度、禁带宽度等因素对太阳电池性能的影响。结果表明:当光吸收层(CH₃NH₃PbI₃)厚度开始增大时电池性能逐渐提高,但是增大到一定厚度时,电池性能下降,光吸收层的最佳厚度为400 nm;当光吸收层的缺陷态密度小于1.0×10¹⁴ cm^-3时,缺陷态密度对电池性能的影响比较小;此外,铅基卤化物钙钛矿的禁带宽度对电池性能有重要影响,最佳禁带宽度为1.5 eV左右。通过模拟,得到了优化后的性能参数为:开路电压为1.010 V,短路电流密度为31.30 mA/cm²,填充因子为80.01%,电池转换效率为25.20%。因此,Cu₂O/CH₃ NH₃PbI₃/Cd_0.5Zn_0.5S钙钛矿太阳电池是一种很有发展潜力的光伏器件。     

金刚石线锯切割多晶硅片的气相制绒研究

采用气相制绒方法对金刚石切割多晶硅片进行表面制绒.2g硅加到HF-HNO3-H2O(400mL,体积比为6:3:1)的酸混合溶液中在室温下反应产生气相,利用气相对金刚石切割多晶硅片表面进行制绒研究.制绒4min时,硅片表面的切割纹被完全去除、大坑套小坑的蜂窝状蚀坑密布硅片表面,减反效果显著,反射率低至19.51%.气相制绒后的金刚石切割多晶硅片表面的微观粗糙度比传统酸混合溶液制绒后的高约20%.     

太阳能多晶硅锭中硬质夹杂及其形成

多晶硅锭中常出现的硬质夹杂是造成硅片线切割生产中断线的主要原因之一,同时影响到太阳能电池片的质量.我们采用扫描电镜-特征X射线能谱仪、3D数码显微镜、傅立叶红外光谱等手段对定向凝固多晶硅断面、抛光面、溶解沉淀以及硅片中的游离碳含量进行了分析.结果表明,硅锭顶表层出现大量SiC和Si3N4夹杂,其数量随深度迅速减小;硅锭内部SiC十分稀少,尺寸也一般很小,但有时会出现大颗粒(～100 μm).硅片中游离碳含量远低于形成SiC所需临界平衡C浓度.就以上结果对SiC形成原因进行了讨论,并提出了减少SiC夹杂的建议措施.     

热丝CVD法沉积固态扩散源制备晶硅太阳电池p+/n+发射极研究

为进一步提高晶硅太阳能电池发射极的性能,本文提出了一种新的发射极制备技术-低温CVD法沉积固态薄膜扩散源并进行高温扩散.采用热丝化学气相沉积法(HWCVD)在单晶硅片上沉积重掺杂硅基薄膜作为固态扩散源,然后在空气氛围下的管式炉中进行高温扩散,最后用稀HF溶液去除表面的BSG/PSG.通过掺磷薄膜扩散在P型单晶硅片上制备了方阻在50～250 Ω/□范围内可控的n+型发射极;通过掺硼薄膜扩散在N型硅片上制备了方阻在150 ～600Ω/□□范围内可控的p+型发射极.并且通过在源气体中加入CO2作为氧源,实现了扩散后硅片表面残留扩散源层的彻底去除.     

直拉单晶硅片“黑心”现象性质分析

对一种黑心片样品进行了分析.在确认黑心区为低少子寿命区的基础上,发现其电阻率明显偏高;发现黑心区经Secco刻蚀后,表面密布重叠圆形蚀坑,但与普通位错蚀坑有明显特征性区别;从其密度、形状与出现条件来看,它与电子半导体业中普遍报告的氧化堆垛层错(OSF)也不一致;进一步发现黑心区经Sirtle刻蚀后,表面呈现典型的大小明显不同的两种漩涡缺陷蚀坑,其密度明显低于上述Secco蚀坑.根据所得结果推测:黑心区主要密布一种性质上与普通位错相近,而所造成晶格畸变特征与范围不同于普通位错的晶格缺陷,它不属于已知的OSF微缺陷,而可能是一种由结晶生长过程中过饱和氧沉淀诱发形成的位错环;此外,黑心区还含有少量漩涡缺陷.