光热退火对多晶PERC太阳电池光致衰减效应的影响

针对多晶PERC电池严重的光致衰减问题,研究不同退火方式对多晶PERC太阳电池光诱导衰减效应的影响,通过设计不同退火条件,对退火后的寿命片和电池片光电性能进行系统表征,发现不同退火条件对多晶寿命片和电池片的光衰有较大影响。通过研究对比确定最佳工艺,可较大程度地抑制多晶PERC太阳电池的光衰效应,同时又不影响电池片的转换效率,为探究抑制多晶PERC太阳电池光衰提供了方法和思路。     

再生处理抑制单晶硅太阳电池光致衰减效应的研究

掺硼晶硅电池经过长时间光照后电池效率会出现明显的衰减。针对此问题,研究再生处理对晶硅电池光致衰减效应的影响。将Si Nx/Al2O3寿命片和单晶钝化发射极和背局域接触(PERC)电池片在400 W/m~2光照下200℃保温10 min进行再生处理,结果发现未经再生处理的寿命片光照1710 min后少子寿命衰减率为63.33%,电池效率衰减率为4.32%,再生处理后样品的衰减率分别降低至5%和0.48%,表明再生处理能有效抑制晶硅电池的光致衰减效应。未经再生处理的寿命片光照前后硼氧(B-O)复合体浓度分别为1.38×1011和7.01×1011cm~(-3),再生处理后的B-O复合体浓度分别为2.90×10~(10)和4.44×10~(10)cm~(-3),再生处理后的寿命片光照后B-O复合体的浓度较处理前低一个数量级,且处于稳定的不会造成少子复合的再生状态。     

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。     

电注入退火对P型直拉PERC单晶硅太阳电池电性能和抗LID效应的影响

以p型直拉PERC单晶硅太阳电池为研究对象,研究了电注入退火在不同的电流、时间和温度条件下,电注入退火前、后太阳电池的各项电性能参数的变化,以及经过5 kWh光致衰减(LID)实验后电池电性能参数的变化,实验均采用Halm电学性能测试仪进行测试和分析。结果表明,在目前的电注入设备条件下,以6.0A的电流在180℃温度下处理35min,最有利于p型直拉PERC单晶硅太阳电池由衰减态向再生态转变;电注入退火后,电池转换效率提升了0.8%;在经过5 kWh LID后,电池的转换效率相对于初始值仅降低了0.71%,证明电注入退火可有效降低p型直拉PERC单晶硅太阳电池的LID效应。     

n型TOPCon-PERT双面太阳电池发电特性分析

随着将隧穿氧化层钝化接触(TOPCon)技术应用在n型钝化发射极背表面全扩散(PERT)太阳电池上,电池效率得到了进一步提升,n型TOPCon-PERT太阳电池因具有少子寿命高、无光致衰减及功率温度系数小等优点,已成为当前太阳电池技术研究的热点之一。通过对比叠加TOPCon技术前、后n型PERT双面太阳电池的量子效率,并根据p型PERC双面光伏组件、n型PERT双面光伏组件及n型TOPCon-PERT双面光伏组件的户外发电特性及衰减率等实测数据,验证了n型TOPCon-PERT双面太阳电池的发电量增益。     

单晶硅PERC高效太阳电池量产工艺研究

以Al_2O_3/Si_xN_y为钝化层,制备了PERC单晶硅太阳电池,研究Al_2O_3钝化层厚度对钝化效果的影响,分析硅片少子寿命变化、烧结曲线对PERC电池电性能参数的影响。     

2020年中国光伏技术发展报告——晶体硅太阳电池研究进展(2)

<正>1.3.5载流子注入退火光衰再生技术近年来,研究人员发现p型晶体硅太阳电池存在光衰(LID)和热辅助光衰(Le TID)现象,这种现象对于p型PERC单晶硅太阳电池而言更加明显。针对这种现象,国内企业普遍采用载流子注入退火工艺对电池进行处理,使电池加速衰退后再恢复,如此一来就减少了电池在出厂后使用时的衰减。目前光伏产业中有2种载流子注入退火工艺,分别为电注入退火和光注入退火。     

P型多晶电池的光致衰减测试

以P型晶硅为基材的太阳能电池片存在着光致衰减,但目前主流的P型多晶电池工艺流程的光致衰减情况却并不确定。文章对电阻率为1～2Ωcm的定向生长P型多晶电池所进行的光致衰减测试和分析发现:光致衰减主要发生在光照射后的3～4 h;采用丝网印刷技术制作的效率为17.1%的多晶电池的绝对效率衰减为0.15%,效率为16.4%的多晶电池的绝对效率衰减为0.08%;并通过热处理可成功地将电池效率恢复。     

Al2O3/SiOxNy/SiNx叠层钝化膜对PERC太阳电池性能及LID效应的研究

由于等离子体增强化学的气相沉积（PECVD）法制备的SiO_xN_y薄膜中含有大量H原子,因而具有优异的表面钝化性能。通过在PERC太阳电池的Al₂O₃/SiN_x背钝化叠层中间插入一层SiO_xN_y薄膜,形成Al₂O₃/SiO_xN_y/SiN_x结构,可避免SiN_x所带的固定正电荷对Al₂O₃负电荷场钝化效应的负面影响。试验结果表明,硅片少子寿命从原来的130 μs提高至162 μs,电池转换效率增加0.09%。同时,基于Al₂O₃/SiO_xN_y/SiN_x背钝化的PERC太阳电池的LID也得到了改善,由对照组的1.83%下降到实验组的1.09%。     

不同温度条件下晶体硅光伏组件光/电致衰减

晶体硅光伏组件存在多种光/电衰减机制，为了研究不同衰减条件的影响，该文首先对不同条件的衰减机理进行探讨；然后进行不同类型的衰减试验，并对试验结果进行分析。通过试验发现，所有类型的太阳电池均有光致或电致衰减现象；相较于PERC太阳电池，TOPCon太阳电池的光致及电致衰减速率较慢，同时在光致衰减（LID）试验中稳定周期最长；在LID试验后，所有类型太阳电池均会发生高温光致衰减。分析电致衰减（CID）与高温光致衰减（LeTID）试验衰减数据，发现组件功率衰减与填充因子变化呈正相关。     

p型铸造单晶硅光注入再生后LID与LeTID的机制分析

光致衰减（LID）与热辅助光诱导衰减（LeTID）是晶硅太阳电池的2种主要衰减,其典型光注入条件分别为25 ℃、1 sun（LID环境）和75 ℃、1 sun（LeTID环境）。从有效少子寿命的角度研究p型铸造单晶硅的衰减机制。200 ℃、7 suns光注入处理过程中样品少子寿命先下降后恢复,这一过程称为光注入再生处理。在LID环境下,无光注入再生处理的样品具有快速与慢速2个衰减阶段,光注入再生处理的样品只有快速衰减阶段。计算两组样品带隙中央附近的缺陷电子/空穴俘获截面比k约为7,表明其中缺陷与直拉单晶硅（Cz-Si）中的BO缺陷相同。对光注入再生处理的样品,在LeTID环境下的衰减阶段计算出k约为35,此数值与多晶硅（mc-Si）中LeTID缺陷的一致。     

开路电压与太阳电池少子寿命关系的推导及其应用的研究

从理论上详细推导了晶体硅太阳电池在脉冲光照下,开路电压Voc(t)与少数载流子寿命的关系,同时研究了N-P结势垒电容放电时对Voc(t)的影响;从实验上验证了开路电压随时间的衰减关系,并运用该关系测量了硅太阳电池少数载流子寿命,测量结果较为准确.     

Characterization of multicrystalline silicon wafers by non-invasive measurements

Non-invasive transient photoconductance measurements of large grain multicrystalline silicon wafers (ρ=1 Ω cm) are presented. It is shown that the surfaces of untreated wafers can be characterized as infinite sinks for excess charge carriers. The value 24.5 cm² s⁻¹ for the minority carrier diffusion constant was determined in all samples. So in untreated wafers, surface recombination yields a known contribution to the decay time measured and the volume lifetime can be determined. Application of these measurements as a standard characterization of multicrystalline silicon wafers is discussed.     

Defect passivation of industrial multicrystalline solar cells based on PECVD silicon nitride

Low surface recombination velocity and significant improvements in bulk quality are key issues for efficiency improvements of solar cells based on a large variety of multicrystalline silicon materials. It has been proven that PECVD silicon nitride layers provide excellent surface and bulk passivation and their deposition processes can be executed with a high throughput as required by the PV industry. The paper discusses the various deposition techniques of PECVD silicon nitride layers and also gives results on material and device properties characterisation. Furthermore the paper focuses on the benefits achieved from the passivation properties of PECVD SiN_x layers on the multi-Si solar cells performance. This paper takes a closer look at the interaction between bulk passivation of multi-Si by PECVD SiN_x and the alloying process when forming an Al-BSF layer. Experiments on state-of-the-art multicrystalline silicon solar cells have shown an enhanced passivation effect if the creation of the alloy and the sintering of a silicon nitride layer (to free hydrogen from its bonds) happen simultaneously. The enhanced passivation is very beneficial for multicrystalline silicon, especially if the defect density is high, but it poses processing problems when considering thin (<200 μm) cells.     

Reduced light reflection of textured multicrystalline silicon via NPD for solar cells applications

Texturing by negative potential dissolution (NPD) process of p-type multicrystalline silicon for solar cells application is reported. The effect of the negative potential, KOH concentration, and texturing time of cast multicrystalline silicon was studied. Rapid texturing of multicrystalline silicon was achieved in a time-frame of 2 min with the application of negative potential of −30 V and the use of optimal alkaline concentration of 32 wt%. While texturing process in these optimal NPD conditions results in a step-free morphology, necessary in solar cells contacts printing, light reflection was reduced to minimal values, as well.     

整形激光掺杂制备PERC电池选择性发射极研究

研究整形激光掺杂制备选择性发射极(SE)对p型单晶硅钝化发射极局域背接触(PERC)太阳电池的表面金字塔形貌、掺杂分布及电池性能的影响。整形激光具有能量分布均匀、对硅片损伤小等优点。通过改变激光的功率以及激光划线速度在p型单晶硅PERC太阳电池制备了不同掺杂分布的发射极。结合3D激光显微镜、扫描电子显微镜、EDS能谱分析、四探针方阻测试仪、电化学电容法等测试分析方法表征了样品的表面形貌、方阻变化、掺杂浓度曲线和电学性能。本文结合光斑重叠率将不同激光功率和激光划线速度采用公式统一转化为激光能量密度,从而得出制备选择性发射极的最佳激光能量密度。研究结果表明,当激光能量密度为0.97 J/cm2时,电池效率可以稳定提升0.25%以上,体现了整形激光SE技术应用于PERC电池的应用潜力。     

The infrared processing in multicrystalline silicon solar cell low-cost technology

New directions in photovoltaics depend very often on financial possibilities and new equipment. In this paper, we present the modification of a standard screen-printing technology by using an infrared (IR) furnace for forming a n⁺/p structure with phosphorus-doped silica paste on 100 cm² multicrystalline silicon wafers. The solar cells were fabricated on 300 μm thick 1 Ω cm p-type multicrystalline Bayer silicon. The average results for 100 cm² multicrystalline silicon solar cells are: I_sc=2589 mA, V_oc=599 mV, FF=0.74, E_ff=11.5%. The cross-sections of the contacts metallized in the IR furnace, as determined by scanning electron microscopy, and the phosphorus profile measured by an electrochemical profiler are shown. IR processing offers many advantages, such as a small overall thermal budget, low power and time consumption, in terms of a cost-effective technology for the continuous preparation of solar cells.     

The influence of annealing conditions on the efficiency of phosphorous gettering in CZ-Si for solar cell applications

The effect of the annealing ambient on the efficiency of the phosphorous gettering process for Czochralski (CZ) silicon wafers is investigated in this paper. Phosphorous is diffused from a POCl₃ source at different temperatures into single-crystal p-type silicon wafers having a resistivity of around 1 ohm/cm. This is followed by an additional heat treatment in either oxidizing (wet and dry oxide) or in inert (argon) ambient. The laser microwave photoconductivity decay method is used to monitor the changes in the minority carrier lifetime after the phosphorous diffusion and the subsequent annealing. Furthermore, solar cells are fabricated on the treated samples in order to correlate the lifetime measurements with the illuminated I-V characteristics of the cells.