扩散p-n结的光电流

对扩散p-n结的光电流在短波长区域的响应进行了解析研究。本文假设扩散p型区的杂质分布为高斯分布,并与前人的指数杂质分布结果作了比较。当用简化的指数杂质分布代替实际的高斯分布,即用一个常值的内建场代替与离表面距离有关的内建场时,对于表面复合相对于体复合为主要因素的p-n结,将引入一个正的光电流误差,反之将引入一个负的光电流误差,而对于表面和体复合两种因素可以比较的p-n结,则引入的误差甚小。     

离子注入技术在n型电池p-n结制备中的应用

介绍了离子注入制备n型电池p-n结的工艺原理及工艺特点,通过对n型硅片和p+发射极主要参数进行模拟分析,得到高效n型电池性能参数的范围及趋势;并对比不同离子注入剂量对n型电池p-n结方阻、implied V_(oc)及J_(0e)的影响,确定了制备高质量n型电池p-n结的离子注入剂量。     

电化离子注入制作硅太阳电池方法的改进

近年来,电化学方法掺杂,除了应用在光电化学电池和电化发光二极管外,也有制作p-n结硅太阳电池的尝试。本工作对电化离子注入方法作了改进。 实验时,以硼酸水溶液为电解液,掺磷的硅片作电化离子注入材料。硅片去污后,用细金钢砂研磨,以减少切割产生的机械损伤,然后再用硝酸、氢氟酸和醋酸的混合液腐蚀,以进一步消除残存在硅片表面层内的微小缺陷。     

硅基薄膜太阳电池(九)

三单结硅基薄膜太阳电池的结构和工作原理1硅基薄膜太阳电池结构在常规的单晶和多晶太阳电池中,通常用p-n结结构。但对于硅基薄膜电池,所用的材料通常是非晶和微晶材料,由于非晶硅内存在大量尾态和悬挂键等缺陷态,载流子的迁移率很低,扩散系数也很低。如果采用通常的p-n结的电池结构,光生载流子在n型和p型中性掺杂区的扩散运动非常小,将直接影响短路电流。此外,由于非晶硅p-n结耗尽层内也存在着大量的缺陷态,会导致势垒区内光生载流子的大量复合。为此,硅基薄膜电池     

背面结构对铝背发射极n型单晶硅太阳电池的影响研究

研究背面结构对铝背发射极n型单晶硅太阳电池的影响,提出背面抛光结构铝背发射极n型单晶硅太阳电池的制备方法。使用少子寿命测试仪、扫描电镜(SEM)、量子效率测试仪及太阳电池测试仪对电池的表面复合速率、微观结构、量子效率和电性能进行测定。结果表明:对铝背发射极n型单晶硅太阳电池,背面抛光结构优于背面金字塔绒面结构,背面抛光结构可降低电池背面的复合速率、改善p-n结质量、提高量子效率,使电池转换效率提高0.34%。     

“SE+PERC”单晶硅太阳电池激光掺杂区域的漏电现象研究

在选择性发射极(SE)技术与钝化发射极背接触(PERC)技术相结合(即“SE+PERC”)的单晶硅太阳电池技术路线中,通常采用激光技术进行局部重掺杂,即利用激光的高温特性将硅片表面磷硅玻璃(PSG)层内的磷原子推入硅片内部,形成高低结,从而提高太阳电池的光电转换效率。但是经过激光扫描后的掺杂区域表面的PSG层会被激光损伤,损伤区域在进行碱抛光时常因掩膜的保护性差而被碱溶液腐蚀,导致p-n结被破坏,造成局部严重漏电,从而影响太阳电池的整体电性能。针对“SE+PERC”单晶硅太阳电池制备过程中激光掺杂区域出现的漏电现象,分析了漏电原因,并给出了采用SE激光掺杂工艺及碱抛光工艺时的优化建议。     

硫化镉太阳电池成结机理的探讨

本文讨论了硫化镉太阳电池p-n结的形成机理。根据所提出的模型及假设,计算了铜—硫化学比的失配量与掺杂浓度的关系和铜处理工艺中蒸铜层的厚度,采用误差补函数扩散模型计算了结深的增长速率。根据予腐蚀电镜照片的形貌,分析计算了结表面的增加量,认为结面积的增加不会使电池的开路电压下降。最后,把计算结果与有关文献及实验数据作了比较。     

利用EDAX方法分析多晶硅电池电极成份

用丝网印刷技术制作多晶硅太阳电池的栅线电极,利用SEM和EDAX测试和分析了金属栅线与硅接触的情况,以及金属与硅界面处各元素的分布,分析了各元素对多晶硅太阳电池p-n结的影响,有利于调整工艺条件来提高电池效率.     

太阳电池工作原理及特性(四)

1.硅太阳电池的能量损失目前,工厂生产的大多数高效硅太阳电池是p-n同质结硅太阳电池。在AMO条件下和20℃时,最高光电转换效率为15％左右。理论上,p-n结硅太阳电池,在AMO条件下所能达到的极限转换效率     

SiNx烧穿工艺下硅太阳电池结构研究

介绍了在全国产设备构成的中试线上开展的高效单晶硅太阳电池研究工作,并制备出了最高转换效率达15.7%的单体电池(面积103×103mm2).实验采用PECVD方法制备SiNx减反、钝化薄膜,并采用正背面电极一次金属化烧结技术,同时完成氮化硅薄膜烧穿工艺.实验还研究了PECVD硅烷与氨气流量比对SiNx钝化、光学和保护性质的影响.分析了氮化硅薄膜及简化新工艺与提高太阳电池效率的关系.实验最后采用化学染色法测量了太阳电池的p-n结结深,结果表明该太阳电池的p-n结为0.25 μm的浅结,直接证明了SiNx薄膜对p-n结有良好的保护作用.     

Plasma-induced TCO texture of ZnO:Ga back contacts on silicon thin film solar cells

This paper considers texturing of ZnO:Ga (GZO) films used as back contacts in amorphous silicon (a-Si) thin film solar cells. GZO thin films are first prepared by conventional methods. The as-deposited GZO surface properties are modified so that their use as back contacts on a-Si solar cells is enhanced. Texturing is performed by simple dry plasma etching in a CVD process chamber,at power=100 W, substrate temperature=190 °C (temperature is held at 190 °C because thin film solar cells are damaged above 200 °C), pressure=400 Pa and process gas H₂ flow=700 sccm. Conventional a-Si solar cells are fabricated with and without GZO back contact surface treatment. Comparison of the with/without texturing GZO films shows that plasma etching increases optical scattering reflectance and reflection haze. SEM and TEM are used to evaluate the morphological treatment-induced changes in the films. Comparison of the a-Si solar cells with/without texturing shows that the plasma treatment increases both the short-circuit current density and fill factor. Consequently, a-Si solar cell efficiency is relatively improved by 4.6%.     

Comparison of multicrystalline silicon surfaces after wet chemical etching and hydrogen plasma treatment: application to heterojunction solar cells

The modifications of the surface and subsurface properties of p-type multicrystalline silicon (mc-Si) after wet chemical etching and hydrogen plasma treatment were investigated. A simple heterojunction (HJ) solar cell structure consisting of front grids/ITO/(n)a-Si:H/(p)mc-Si/Al was used for investigating the conversion efficiency. It is found that the optimized wet chemical etching and cleaning processes as a last technological step before the deposition of the a-Si:H emitter are more favorable to HJ solar cells fabrication than the hydrogenation. Solar cells on p-type mc-Si were prepared without high-efficiency features (point contacts, back surface field). They exhibited efficiencies up to 13% for a cell area of 1 cm² and 12% for a cell area of 39 cm².     

Technological process for a new silicon solar cell structure with honeycomb textured front surface

This paper presents a new silicon solar-cell structure improved by texturisation of the front surface using silicon micromachining technologies. A ‘honeycomb’-textured front surface has been obtained through a photolithographical process to generate patterns (disc holes) on the front surface followed by isotropic etching (in HNO₃: HF: CH₃COOH) until the wells joined together.For front-surface loss characterisation, the spectral dependence of the front-surface reflectivity has been investigated by spectrophotometrical measurements. The surface reflectivity was lowered under 10% and this value was a good one compared to the reflectivity of silicon monocrystalline wafer untextured surface. The p–n junction made by phosphorous diffusion at 0.8 μm follows the honeycomb profile. In order to obtain low series resistance, a p+ boron diffusion on the back of the structure was made. The fabrication process was completed with an ohmic contact (Al on top and on the back surface).     

Processing options for CdTe thin film solar cells

Processing options for addressing critical issues associated with the fabrication of thin film CdTe solar cells are presented, including window and buffer layer processing, post-deposition treatment, and formation of stable low resistance contacts. The paper contains fundamental data, engineering relationships and device results. Chemical surface deposited CdS and Cd_1−xZn_xS films are employed as the n-type heteropartner window layers. Maintaining junction quality with ultra-thin window layers is facilitated by use of a high resistance oxide buffer layer, such as SnO₂, In₂O₃ or Ga₂O₃, between the heteropartner and the transparent conductive oxide. Thermal annealing of the CdTe/CdS heterostructure in the presence of CdCl₂ and O₂ shifts the chemical equilibrium on the surface of the absorber layer, which influences the bulk electrical properties. Aspects of back contacting CdTe/CdS devices, including etching, Cu application, contact annealing, back contact chemistry and secondary contacts, are discussed. Two commonly employed etches used to produce a Te-rich layer, nitric acid/phosphoric acid mixtures and Br₂/methanol are compared, including the nature and stability of the final treated CdTe surface. The diagnostic abilities of the surface sensitive VASE and GIXRD techniques are highlighted. Various methods of Cu delivery are discussed with consideration to; reaction with Te, processing simplicity, processing time and possible industrial scale-up. Some aspects of back contact stability are presented, including discussion of apparent robust back contacts, which contain a thick Te component.     

16.0% Efficiency of large area (10 cm×10 cm) thin film polycrystalline silicon solar cell

High efficient large area thin film polycrystalline Si solar cell based on a silicon on insulator (SOI) structure prepared by zone-melting recrystallization (ZMR) is reported. Fabrication process of the via-hole etching for the separation of thin films (VEST) is newly developed. It is found that phosphorus treatment and back surface field (BSF) are quite effective for the VEST structure and the ZMR thin film polycrystalline silicon. The conversion efficiency as high as 16.0% for a practical size (10 cm×10 cm) is achieved. This is the highest for large area thin film polycrystalline Si solar cells ever reported.     

Improvement on surface texturing of single crystalline silicon for solar cells by saw-damage etching using an acidic solution

Texturing the surfaces of silicon wafer is one of the most important ways of increasing their efficiencies. The texturing process reduces the surface reflection loss through photon trapping, thereby increasing the short circuit current of the solar cell. The texturing of crystalline silicon was carried out using alkaline solutions. Such solutions resulted in anisotropic etching that leads to the formation of random pyramids. Before the texturing process was carried out, saw-damage etching was performed in order to remove the surface defects and damage caused by wire sawing. In general, potassium hydroxide (KOH) solution has been used for saw-damage etching. This etching results in a fairly flat surface. The results from this study showed that the outcome of the surface texturing is related to the original surface morphology of the silicon. It was found that saw-damage etching using an acidic solution improved the effects of the texturing. In this case, regular and small pyramids were formed on the surface of the silicon. This reduced the reflectance of the surface, thereby increased the short circuit current and the conversion efficiency of the solar cell.     

Light trapping and optical losses in microcrystalline silicon pin solar cells deposited on surface-textured glass/ZnO substrates

Influence of front TCO thickness, surface texture and different back reflectors on short-circuit current density and fill factor of thin film silicon solar cells were investigated. For the front TCO studies, we used ZnO layers of different thickness and applied wet chemical etching in diluted HCl. This approach allowed us to adjust ZnO texture and thickness almost independently. Additionally, we used optical modeling to calculate optical absorption losses in every layer. Results show that texture and thickness reduction of front ZnO increase quantum efficiency over the whole spectral range. The major gain is in the red/IR region. However, the higher sheet resistance of the thin ZnO causes a reduction in fill factor. In the back reflector studies, we compared four different back reflectors: ZnO/Ag, Ag, ZnO/Al and Al. ZnO/Ag yielded the best, Al the worst light trapping properties. Furthermore, the Ag back contact turned out to be superior to ZnO/Al for microcrystalline cells. Finally, the smooth ZnO/Ag back contact showed a higher reflectivity than the rough one. We prepared pin cells with rough and smooth ZnO/Ag interface, leaving the roughness of all other interfaces unchanged.     

Anodic and optical characterisation of stain-etched porous silicon antireflection coatings

Porous silicon (PS) antireflection coatings have been obtained by stain etching of crystalline Si in HF:HNO₃:H₂O solutions at different etching times and HNO₃ concentrations. The morphology of the PS samples was characterised by anodic oxidation and revealed the increase of the porous surface area with the HNO₃ concentration. Upon a certain critical concentration of HNO₃, the surface of crystalline Si immersed in the solution becomes polished, and a decrease of its surface area is observed. The samples were also characterised by a spectrophotometer in the range 300–900 nm, showing an effective reflectance below 4% in most of the spectral range for samples obtained in an etching solution, where the HNO₃ is below its critical concentration. Anodic oxidation after etching can be used as an useful tool for the qualitative and quantitative analysis of porous surface areas.     

ZnO:Al绒面透明导电薄膜的制备及分析

利用中频脉冲磁控溅射方法,采用Al掺杂(质量百分比2%)的Zn(纯度99.99%)金属材料为靶材制备平面透明导电ZnO:Al(ZAO)薄膜。利用湿法腐蚀方法,将平面ZAO薄膜在0.5%的稀盐酸中浸泡一定时间后,形成表面凹凸起伏的绒面结构。研究了平面ZAO薄膜的结构特性以及衬底温度、溅射功率和腐蚀时间对绒面ZAO薄膜表面形貌的影响,并对腐蚀前后薄膜的电阻变化进行了分析。结果表明:高温、低功率条件下制备的绒面ZAO薄膜表面形貌较好,在硅薄膜太阳电池中具有潜在的应用前景。     

The noble metal loading binary iron–zinc electrode for hydrogen production

The binary FeZn was electrodeposited on graphite surface for hydrogen evolution reactions. Then, zinc was leached from the surface by an etching method in alkaline solution. A trace amount of platinum and ruthenium electrochemically deposited on binary FeZn, respectively. All electrodes were characterized by cyclic voltammetry, electrochemical impedance spectroscopy and potentiodynamic polarization techniques in KOH solution. The surface structures were characterized by scanning electron microscopy and energy dispersive X-ray. The results show that etching process enhanced the surface area. The prepared electrodes exhibited much higher activity after noble metal loadings. It is seen from experimental research that the most active electrode is C@FeZn/Ru.