氮化硅薄膜对硅片背表面的钝化作用

采用等离子体增强化学沉积的方法(PECVD),在低衬体温度下制备不同厚度的双面氮化硅薄膜,通过准稳态电导法(QSSPCD)测试non-diffused和diffused硅片沉积不同厚度双面氮化硅薄膜烧结前后的少子寿命,研究发现,氮化硅薄膜厚度在17 nm左右的时候,背面钝化效果有所下降,超过26 nm的时候,效果基本一致.non-diffused烧结后的少子寿命下降很大,而diffused与之相反.结果表明,采用氮化硅作为背面钝化介质膜,可以改善材料的少子寿命,背面钝化膜可以选择在26～75 nm之间.     

高效PERC单晶硅太阳电池局部背表面场的工艺研究

钝化发射极和背面电池(PERC)的局部背表面场是指通过对电池背面的钝化层进行激光开槽形成局部接触。研究了激光参数设置和激光图形对电池背表面场局部接触的影响,根据电池转换效率来确定最佳的激光参数和激光图形。用奥林巴斯显微镜分析了在不同激光速度和不同激光实线比条件下,电池的背面铝浆填充率的变化;用Halm电学性能测试仪分析了在不同背面铝浆填充率和不同激光间距,以及背电极是否被激光覆盖这些条件下,电池电性能的变化趋势。结果表明,背面铝浆填充率为35%时,电池转换效率最佳。再根据不同激光速度和不同激光实线比的正交试验,反推出当激光速度为16000 m/s、激光实线比为50%时,更有利于提升电池转换效率;当激光开槽间距为1275μm时,电池转换效率最佳;背电极激光镂空与激光填满实验相比,背电极激光镂空的电池转换效率可增加约0.06%。     

晶体硅太阳电池背面套印图形设计对电池性能和组件性能的影响

以晶体硅太阳电池背面套印图形为研究对象,通过设计背电场和背电极套印方式以及背电极图形,对背面不同套印图形的接触电阻、电池的电性能和组件性能进行研究。研究结果表明:背面铝背场和银电极在重叠面积为4.35%,且背电极蜈蚣脚间距为1 mm时的接触电阻最小,电池效率提升最大,同时组件输出功率增益最多。该研究为晶体硅太阳电池背面套印图形设计和背电极图形的优化提供指导。     

背钝化膜特性对PERC单晶硅太阳电池的影响研究

研究了氧化铝膜与氮化硅膜厚度,以及氮化硅折射率对PERC单晶硅太阳电池电性能的影响,结果表明,氧化铝膜较薄、氮化硅膜较厚时,PERC单晶硅太阳电池的V_(oc)与I_(sc)明显提高,电池效率提升明显;并且结合不同工艺参数的少子寿命及量子效率,证明了背钝化膜钝化作用的优势。     

SiNx:H/Al复合膜层在背点接触太阳电池中的应用

尝试将SiNx∶H/A1复合膜层应用到晶体硅太阳电池的背部结构上.首先利用PECVD在硅片背面沉积一层SiNx∶H薄膜,然后在SiNx∶H薄膜上丝网印刷Al层,构成SiNx∶H/A1复合膜层.研究了具有SiNx∶H/Al复合膜层结构的硅片的光学内背反射性能,测得其内背反射率达88.9%.并从理论上设计出基于SiNx∶H/A1复合膜层的背点接触太阳电池最优结构,并从实验上制备出这种背点接触太阳电池,初期效率达12.36%.最后,提出了背点接触太阳电池工艺的改进方案.     

激光开槽对MWT+PERC单晶硅太阳电池性能影响的研究

金属缠绕穿透(MWT)技术和钝化发射极及背接触(PERC)技术叠加应用可获得较高的硅太阳电池转换效率,且可以降低硅材料的损耗,但不同的背面激光开槽工艺会对电池的电性能产生不同影响。在保证同批次单晶硅片的背面开槽率(2.10%)不变时,针对MWT+PERC单晶硅太阳电池工艺中的背面激光开槽工艺进行了研究。通过调节激光功率的大小来改变开槽宽度与开槽线间距的大小,从而探究不同开槽图形对MWT+PERC单晶硅太阳电池电性能的影响;同时在3D显微镜下观察不同开槽宽度时硅片表面的激光光斑质量,并采用扫描电子显微镜(SEM)观察不同开槽宽度时这类电池烧结后局部接触区域的形貌。结果表明,开槽宽度在33～35μm、开槽线间距为0.90±0.05 mm时,MWT+PERC单晶硅太阳电池的电性能及开槽形貌质量最佳。     

硅片厚度对SE-PERC单晶硅太阳电池制备过程的影响分析

基于目前主流的选择性发射极-钝化发射极及背接触(SE-PERC)单晶硅太阳电池生产工艺,针对不同硅片厚度在太阳电池制备过程中的表现进行分析、验证及优化.研究结果表明,硅片厚度减薄对湿法刻蚀工艺后硅片的减重、硅片背面抛光效果均有显著的不良影响,而且采用管式PECVD工艺沉积的SiNx薄膜的厚度也出现变薄的现象.若太阳电池...     

PERC背面银浆性能研究

通过研究三种不同背面银浆的性能,发现三种背面银浆的黏度、细度、拉力性能均比较接近,而PERC背面银浆的固含量比普通背面银浆高,方阻比普通背面银浆低。不同背面银浆最大的性能差异在于其对PERC电池钝化层的破坏程度不同。通过电性能测试我们发现普通背面银浆制备的PERC电池Eff低0.4%左右,说明普通背面银浆不能用于PERC电池的制备。通过EL定量分析的方法我们发现,普通背面银浆的灰度值显著低于PERC背面银浆,说明其对钝化层的破坏程度大,这与电性能测试数据吻合。     

氮化硅薄膜对晶体硅材料和电池的钝化效果研究

利用等离子体增强化学气相沉积技术,在P型直拉单晶硅硅片和铸造多晶硅片以及太阳电池的表面上 沉积了非晶氮化硅(a-SiNx:H)薄膜,并研究了氮化硅薄膜对材料少子寿命和太阳电池性能的影响。研究发现: 氮化硅薄膜显著地提高了晶体硅材料中少子寿命,同时多晶硅太阳电池的开路电压有少量提高,短路电流普遍 提高了1mA/cm2,电池效率提高了2％。实验结果表明:氮化硅薄膜不仅具有表面钝化作用,也有良好的体钝化 作用。     

板式PECVD设备维护后初期的生产品质提升方案

以板式PECVD设备维护后的初期在多晶硅片表面镀的氮化硅薄膜为研究对象,分析了其膜厚、折射率、腐蚀速率等数据,以及此种镀膜情况下制备的多晶硅太阳电池的电性能.结果表明:在设备维护后初期(约1 h)镀制的氮化硅薄膜,随着时间的推移,氮化硅薄膜的膜厚不断下降,折射率随之上升,二者分别从第48 min和第56 min开始趋于...     

多晶PERC太阳电池的背面与正面结构性能优化

多晶硅太阳电池以其价格低廉的优势成为低成本太阳电池的首选,但其光电转换效率提升空间有限。钝化发射极和背面电池（PERC）技术是当前晶硅太阳电池提效的主要途径。多晶PERC电池结合了多晶硅电池的低成本和PERC电池的高效,是当前多晶硅电池的研究热点。本文研究了多晶PERC电池的背面和正面结构优化与设计,提出了提高多晶PERC电池效率的产业化技术方法。通过在硅片背面用三层SiN_x:H薄膜来代替常规双层SiN_x:H薄膜,在保证优良的背面钝化的同时,使电池长波响应得到改善,电池光电转换效率由20.19% 提升至20.26%。优化多晶PERC电池的背面激光开窗工艺,使多晶电池效率较常规工艺提升0.11%。而在多晶PERC电池的正面叠加选择性发射极技术,可较常规工艺提升电池效率0.10%。综合运用多种提效手段有利于保持多晶PERC电池的竞争力。     

Recent developments in rear-surface passivation at Fraunhofer ISE

Fraunhofer ISE has a long experience in the field of surface passivation for crystalline silicon wafers. Novel rear-surface passivation layer systems have led to excellent results. Using a low-temperature passivation stack of hydrogenated amorphous silicon and plasma-enhanced chemical vapor deposition (PECVD) silicon oxide an efficiency of up to 21.7% has been achieved. Thermally stable passivation can be proven with all-PECVD stacks of silicon oxide, silicon nitride, and silicon oxide (PECVD-ONO), i.e. after contact firing. Solar cell efficiencies of up to 20.0% have been reached with PECVD-ONO. In parallel, Fraunhofer ISE is working on silicon carbide (SiC_x) layers, which provide excellent and thermally stable passivation, as well deposited by PECVD. Solar cells with SiC_x layers as rear passivation led to efficiencies of up to 20.2%.     

Cost effective process for high-efficiency solar cells

A new method for patterning the rear passivation layers of high-efficiency solar cells with a mechanical scriber has been developed and successfully adapted to fabricate high-efficiency passivated emitter and rear cell (PERC). Three types of the rear contact patterns: dot patterns with a photolithography process, line and dashed line patterns with a mechanical scriber process have been processed in order to optimize the rear contact structure. An efficiency of 19.42% has been achieved on the mechanical-scribed (MS)-PERC solar cell on 0.5 Ω cm p-type FZ-Si wafer and is comparable to that of conventional PERC solar cells fabricated by using photolithography process. The mechanical scriber process shows great potential for commercial applications by achieving high efficiency above 20% and by significantly reducing the fabrication costs without an expensive photolithography process. Low-cost Ni/Cu metal contact has been formed by using a low-cost electroless and electroplating. Nickel silicide formation at the interface enhances stability and reduces the contact resistance resulting in an energy conversion efficiency of 20.2% on 0.5 Ω cm FZ wafer.     

Characterization of high open-circuit voltage double sided buried contact (DSBC) silicon solar cells

The double sided buried contact (DSBC) silicon solar cells have consistently shown high open-circuit voltages (V_oc) than its single sided buried contact counterpart because of better rear surface passivation. The rear surface passivation which is provided by the rear floating junction is effective only when there is no leakage in the rear floating junction. However, the partial shunting of the rear floating junction can cause a drop in the fill factor of the cell which has been the only parameter limiting the realization of the structure's potentials. In this paper, LBIC (light beam induce current), spectral response, dark I-V and J_sc-V_oc measurements for DSBC cells have been carried out to help explain some of the experimentally observed attributes of this structure. The partly shunted rear floating junction has been identified by LBIC measurement as low current regions near the rear metal contacts.     

685 mV open-circuit voltage laser grooved silicon solar cell

The recombination limiting the voltage of the present buried contact solar cell (BCSC) can be reduced by replacing the present high recombination sintered aluminium back with a floating rear junction for passivation, heavy boron diffusion below the rear contact, and by limiting the rear surface contact area. Analysis of these implementations in the double sided laser grooved (DSLG) structure shows that the floating junction passivation is effective in reducing the recombination component at the rear surface and that the boron diffusion in the rear groove comprises up to half of the total saturation current. Limiting the area of the heavily diffused boron grooves allows open-circuit voltages of 685 mV while maintaining the simplicity of the BCSC processing sequence. An open-circuit voltage of 685 mV represents nearly a 50 mV increase over the conventional BCSC.     

Improving the performance of textured silicon solar cells through the field-effect passivation of aluminum oxide layers and up-conversion via multiple coatings with Er/Yb-doped phosphors

This paper examines the influence of field-effect passivation (from a coating of aluminum oxide) in conjunction with up-conversion (from multiple coatings containing Er/Yb-doped phosphors) on the performance of silicon solar cells. Note that the phosphors were applied to the rear surface of the cells. The surface morphology of the coatings was characterized by scanning electron microscopy and the chemical composition of Er/Yb-doped phosphors coating was examined using energy-dispersive X-ray spectroscopy. The fluorescence emissions of the coatings were examined using photoluminescence and optical image measurements. We examined the influence of field-effect passivation on dark current-voltage as well as photo-current density and external quantum efficiency (EQE). Improvements in photovoltaic performance after applying coatings containing Er/Yb-doped phosphors were estimated in terms of EQE and conversion efficiency. The field-effect passivation of Al₂O₃ and up-conversion provided by Er/Yb-doped phosphors resulted in EQE enhancements over a wavelength range of 600 to 1050 nm. Field-effect passivation was shown to enhance the conversion efficiency by 1.77% (from 16.91% to 17.21%), up-conversion enhanced conversion efficiency by 2.9% (from 17.21% to 17.71%), and a combination of field-effect passivation and up-conversion enhanced conversion efficiency by 4.73% (from 16.91% to 17.71%).     

Laser fired contacts applied to the rear surface of heterojunction silicon solar cells

In this work, we fabricate heterojunction silicon solar cells on p-type substrates whose rear surface configuration is based on dielectric passivation and laser fired contacts (LFC cells). This is an alternative to boron-doped amorphous silicon film, with which we also fabricate solar cells for direct comparison (HJ cells). As substrates, 3.5 and 0.8 Ω cm p-type double-side polished FZ c-Si wafers are used. Regarding surface passivation for highly doped substrates, LFC configuration has some advantage due to the higher difficulty in creating an efficient amorphous back surface field. Additionally, those substrates are also more advantageous in terms of carrier injection when the rear surface is locally contacted. Thus LFC cells made on 0.8 Ω cm substrates reach V_oc values up to 680 mV, in the same range as that of their HJ cell counterpart, with better FF demonstrating that LFC configuration is a feasible alternative for highly doped substrates. Focusing on the impact of the distance between rear contacts on cell performance, we found a trade-off between open circuit voltage V_oc and fill factor FF. Finally electroluminescence characterization and the dependence of V_oc on pitch, modeled by Fischer's equation, indicate that the depassivated area due to the laser processing of the contacts is bigger than the contacted area.     

An industrial solution to light-induced degradation of crystalline silicon solar cells

Boron-oxygen defects can cause serious light-induced degradation (LID) of commercial solar cells based on the boron-doped crystalline silicon (c-Si), which are formed under the injection of excess carriers induced either by illumination or applying forward bias. In this contribution, we have demonstrated that the passivation process of boron-oxygen defects can be induced by applying forward bias for a large quantity of solar cells, which is much more economic than light illumination. We have used this strategy to trigger the passivation process of batches of aluminum back surface field (Al-BSF) solar cells and passivated emitter and rear contact (PERC) solar cells. Both kinds of the treated solar cells show high stability in efficiency and suffer from very little LID under further illumination at room temperature. This technology is of significance for the suppression of LID of c-Si solar cells for the industrial manufacture.     

The use of silicon nitride in buried contact solar cells

Silicon nitride offers many potential benefits to the family of buried contact fabrication sequences including improved design flexibility and efficiency. The main device structures of the buried contact family comprise the standard buried contact, the simplified buried contact and the double-sided buried contact cells. The physical properties of silicon nitride allow it to be used for surface passivation, as an anti-reflection coating, as a diffusion source material and as a masking dielectric. The use of silicon nitride in each buried contact fabrication sequence is described in this work.     

Low temperature passivation of silicon surfaces by polymer films

A novel surface passivation method for silicon carrier lifetime measurements and solar cells using a polymer film is introduced. It is easy to apply, no special pre-treatment, e.g. no hydrofluoric acid (HF)-treatment, is necessary. The surfaces to be passivated are covered with the polymer solution, dried at 90°C and encapsulated. Surface recombination velocities (S) as low as S=30 cm/s for various doping concentrations have been observed, nearly independent of the bulk injection level. The passivation is stable for at least 6 h. For a polymer-passivated rear contact solar cell the same open circuit voltage is achieved as for a cell with thermally grown oxide.