Polycrystalline silicon solar cell manufacture craft outline It is well known,will have many merits using the solar energy,the light bends down the electricity generation to provide the main energy for the humanity,but at present says,will have enable the solar energy electricity generation to have the big market,by general consumer acceptance,is enhanced the solar cell the photoelectricity transfer efficiency,reduces biggest goal which the production cost should be we pursues,may see its trend of development from at present international solar cell developing process for the monocrystalline silicon,the polycrystalline silicon,the belt-shaped silicon,the membranous material(including micrite silicon-based thin film,compound base thin film and dye thin film).Looked from the industrialization development that,the center of gravity has developed by the unit crystal to the polytropism direction,the primary cause is;[1]may supply the solar cell to expect from beginning to end few increasingly;[2]says to the solar cell,the square shape substrate is more worthwhile,obtains the polycrystalline silicon through the casting law and the direct coagulation law to be possible to obtain the square shape material directly;The[3]polycrystalline silicon production craft makes the progress unceasingly,the completely automatic casting stove each production cycle(50hours) may produce200kilogram above silicon spindles,the crystal grain size achieves a centimeter level;Because[4]near ten year monocrystalline silicon craft the research and development are very quick,in which craft is also applied in the polytropism silicon cell production,for example the choice corrosion launch knot,the back surface field,the corrosion fabric surface,superficial and the body deactivation,the thin wire netting electrode,uses the silk-screen printing technology to be possible to cause the grid electrode the width to reduce to50microns,achieved highly above15microns, the fast hot annealing technology uses in the polycrystalline silicon the production being possible to reduce the craft time greatly,the monolithic hot working procedure time may complete in a minute,uses this craft the battery transfer efficiency which makes on100square centimeter polytropism silicon chips to surpass14%.According to the report,at present the battery efficiency which manufactures on50~60micron polycrystalline silicon substrates surpasses16%.Using the mechanical chamfer,the silk-screen printing technology the efficiency surpasses17%in100square
centimeters polytropisms,the non-mechanical chamfer the efficiency achieves16%in the similar area,uses buries the grid structure,the mechanical chamfer the battery efficiency achieves15.8%in130square centimeters polytropisms.
Below carries on the discussion from two aspects to the polytropism silicon cell processing technology.
2.The laboratory highly effective battery craft
Laboratory technology usually did not consider the battery manufactures cost and whether can the big formalization production,study merely achieved the peak efficiency the method and the way,provide the limit which the specific material and the craft can achieve.
2.1about the light absorption;
Regarding the light absorption mainly is;
(1)reduces the superficial reflection;
(2)change light in battery in vivo way;
(3)uses reflects.
Regarding the monocrystalline silicon,the method which application aeolotropic chemistry corrodes may manufacture the pyramid shape in(100)surface the fabric surface structure,reduces the superficially attractive reflection.But the polycrystalline silicon lattice orientation deviates(100),uses above method to be unable to make the even fabric surface,at present uses the following method:
[1]laser chamfer
With the laser chamfer method may in the polycrystalline silicon surface manufacture pyramid structure,in the500~900nm spectrum scope,the index of reflection be but actually4~6%,double-decked reduces the reflection membrane with the superficial manufacture quite.But in(100)monocrystalline silicon chemistry manufacture fabric surface index of reflection is11%.Compared to plates double-decked with the laser manufacture fabric surface in the smooth surface reduces the reflection film(ZnS/MgF2)battery the short-circuit current to have to enhance about4%,this mainly is the long wave light(wave length is bigger than 800nm)the oblique incidence to enter the battery the reason.The laser manufacture fabric surface existence question is in the sculpture,the surface creates the damage
simultaneously to introduce some impurities,must through chemistry processing elimination superficial injury level.This method does the solar cell usual short-circuit current is high,but the open-circuit voltage not too high,the primary cause is the battery surface area increases,causes the recombination current enhancement.
[2]chemistry chamfer
(Si3N4or SiO2)the isotropism corrodes using the mask,the corrosive liquid may be the acidic corrosive liquid,also may for the density high sodium hydroxide or the potassium hydroxide solution,this method is unable that kind of sharp pyramidal structure which forms the aeolotropy to corrode forms.According to the report,the fabric which this method forms has obviously facing700~1030micron spectrum scopes reduces the reflex action.But the mask level must form generally under the high temperature,causes the polycrystalline silicon material performance to drop, specially to quality low polytropism material,youngest son loss of life.Makes the battery using this craft in the225cm2polycrystalline silicon the transfer efficiency to achieve16.4%.Mask level also available silk-screen printing method formation.
[3]responded the ion corrodes(RIE)
This method is one kind of non-mask corrosion craft,forms the fabric surface index of reflection is specially low,may be smaller than2%in450~1000micron spectrum scope index of reflection.Only looked from optics angle that,is one ideal method,but exists the question is the silicon superficial injury is serious,the battery open-circuit voltage and the packing factor appears the drop.
[4]manufacture reduces the reflection film
Regarding the highly effective solar cell,most commonly used and the most effective method is evaporation ZnS/MgF2double-decked reduces the reflection membrane,its best thickness is decided by under oxide layer thickness and the battery surface characteristic,for example,the surface is the smooth surface or the fabric surface,reduces the reflection craft also to have evaporation Ta2O5,PECVD deposits Si3N3and so on.The ZnO conductive coating also may take reduces the counter-material.
2.2metallized technologies
In the highly effective battery manufacture,the metallized electrode must with the battery design variable,like the superficial doping density,PN tie the depth,the metal material matches.The laboratory battery general area quite is small(area to be smaller than4cm2),therefore needs the thin metal grating(to be smaller than10 microns),uses generally the method for the photoetching,the electron beam evaporates,the electron plates.In the industrialization big production also uses the galvanization craft,when evaporation and photoetching union use,does not belong to the low cost processing technology.
electron beam evaporation and the galvanization:
Is usual,applies the rubber peeling craft,the evaporation Ti/Pa/Ag multi-layer metal electrode,must reduce the series resistance which the metal electrode causes, often needs the conductive sea quite to be thick(8~10microns).The shortcoming is the electron beam evaporation creates the silicon surface/deactivation level interface damage,causes the surface recombination enhancement,therefore,in the craft,uses short-time evaporates the Ti/Pa level,in evaporation silver level craft.Another question is when the metal and the silicon contact face are big,will certainly to cause the youngest son compound speed enhancement.In the craft,used the tunnel to tie the contact the method,became in the silicon and the metal forms a thin oxide layer (general thickness is about20microns)the application work function low metal(for example titanium and so on)may induce a stable electronic accumulation level in the silicon surface(also to be possible to introduce fixed positive charge to deepen counter-).Moreover one method is starts out the small window on the deactivated level(to be smaller than2microns),again the deposition wide metal grating(usually is10microns),forms the mushroom-like shape electrode,the battery transfer efficiency achieves17.3%with this method on4cm2Mc-Si.At present,also has utilized the formation technology in the mechanical scored surface which Shallow angle(oblique)technical.
2.3PN ties
[1]launch area forms with the phosphorus attracts mixed
Regarding the highly effective solar cell,the launch area formation generally uses the choice proliferation,but formed the heavy impurity region underneath the
metal electrode to realize the shallow density proliferation in the electrode between, the launch area shallow density proliferation namely strengthened the battery to the blue light response,also caused the silicon surface easy to deactivate.The proliferation method has two step diffusion technologies,the proliferation adds the corrosion craft and the bury diffusion technology.At present uses the choice proliferation,15×15cm2 the battery transfer efficiency achieves16.4%,n++,the n+region superficial block resistance respectively be20Ω;and80Ω.
Regarding the Mc-Si material,expands the phosphorus to attract mixed the influence obtains the extensive research to the battery,the long time phosphorus attracts the mixed process(general3~4hours),may make some Mc-Si the youngest son diffusion length to enhance two number magnitudes.In to attracts the mixed effect to the substrate density in the research to discover,even if to highly concentrated lining material,After attracts mixed also can obtain the big youngest son diffusion length(to be bigger than200microns),the battery open-circuit voltage is bigger than 638mv,the transfer efficiency surpasses17%.
[2]back surface field formation and the aluminum attract the mixed technology
In the Mc-Si battery,carries p+p to tie by the even proliferation aluminum or the boron formation,the boron source is generally BN,BBr,APCVD SiO2:B2O8and so on,the aluminum proliferation for the evaporation or the silk-screen printing aluminum,800degrees under agglutinations complete,attracted the mixed function to the aluminum also to carry out the massive research,attracted mixed with the phosphorus proliferation different,the aluminum attracted carries on mixed under the relative low temperature.Body flaw also participated in the impurity dissolution and the deposition,but under the high temperature,the deposition impurity easy to dissolve enters in the silicon,has the disadvantageous influence to Mc-Si.To at present for to,the region back field has applied in the unit crystal silicon cell craft,but in polycrystalline silicon,applies the entire aluminum back surface field structure.
[3]two-sided Mc-Si battery
Mc-Si two-sided battery it is directly the conventional structure,back is N+and the P+intercross structure back,but like this,the positive illumination produces is located nearby photoproduction youngest son to be possible to absorb effectively by
the back electrode.The back electrode takes to the positive electrode effective supplement,also took independent plants the current collector has the function to the back illumination and the diffused light,according to the report,under the AM1.5 condition,the transfer efficiency surpasses19%.
2.4superficial and body deactivation technologies
Regarding Mc-Si,because has the high crystal boundary,the spot flaw(vacancy, caulking atom,metal impurities,oxygen,nitrogen and their compound)especially is important to the material surface and in vivo flaw deactivation,mentions besides front attracts the mixed technology,the deactivated craft has many kinds of methods, causes the silicon hand key saturated through the thermal oxidization is one quite commonly used method,may cause the Si-SiO2contact surface the compound speed to drop greatly,Its deactivated effect is decided by the launch area surface concentration,the contact surface density of states and the electron,the hole floats attains the section.The annealing may cause the deactivated effect in the hydrogen atmosphere to be more obvious.Will use the PECVD deposition silicon nitride directly extremely to be effective in the near future,because in will become the membrane in the process to have the hydrogenation effect.This craft also may apply in the formalization production.May cause the surface recombination velocity using Remote PECVD Si3N4to be smaller than20cm/s.
3industrialization battery craft
The solar cell moves towards the factory from the laboratory,the experimental study moves towards the formalization production is its development path,therefore can achieve the industrialization production the characteristic should be:
[1]battery manufacture craft can satisfy the assembly line work;
[2]can large-scale,the modernized production;
[3]achieves,the low cost highly effective.
Certainly,its essential target is reduces the solar cell the production cost.At present the polytropism silicon cell main development direction is facing the big area, the thin substrate.For example,in the market obviously arrives125×125mm2, 150×150mm2even the large-scale monolithic battery,thickness reduces from the original300microns to at present250,200and below200microns.The efficiency
obtains the large scale enhancement.The Japanese Beijing Magnetism(Kyocera) Corporation150×150battery small batch production photoelectricity transfer efficiency achieves17.1%,this company1998productivity achieved25.4MW.
(1)silk-screen printing and related technology
In the polytropism silicon cell formalization production has widely used the silk-screen printing craft,this craft available in proliferation source printing,positive metal electrode,back contact electrode,reduces the reflection film and so on,along with the silk screen material improvement and the technological level enhancement, the silk-screen printing craft will be able to obtain a more universal application in the solar cell production.
https://www.doczj.com/doc/129210477.html,unch area formation
Forms the PN knot using the silk-screen printing,replaces conventional the pipe heater diffusion technology.Generally in polycrystalline silicon frontage printing including the phosphorus pulp,contains the aluminum metal pulp in reverse side printing.After printing completes,the proliferation may complete(usual temperature in the net belt stove in900degrees),like this,printing,drying,the proliferation may form the continuous production.The silk-screen printing proliferation technology forms the launch area usual surface concentration quite is high,then superficial photoproduction current carrier compound big,in order to overcome this shortcoming, in the craft has used following choice launch area processing technology,enable the battery the transfer efficiency to obtain the further enhancement.
b.choice launch area craft
In the polytropism silicon cell diffusion technology,the choice launch area technology divides into the localized corrosion or two steps the diffusion process.The localized corrosion for uses the dry process(e.g.response ion to corrode)the method which or chemistry corrodes,metal electrode between region heavy diffusion layer perish.At first,Solarex the method which corrodes using the response ion in the identical Taiwan equipment,first uses the heavy doping level between the big response power perish metal electrode,then uses the low power to deposit a silicon nitride thin film,This film display reduces the reflection and the battery surface deactivation dual function.Makes the transfer efficiency in the100cm2polytropism to
surpass13%battery.In the similar area,applies two diffusion processes,has not made the mechanical fabric surface in the situation the transfer efficiency to achieve16%.
c.back surface field formation
Carries PN to tie usually the hot annealing forms by the silk-screen printing A pulp and after the net belt stove,this craft while forms which the back surface ties,has the good ablution function to in the polycrystalline silicon impurity,the aluminum attracts the mixed process to complete generally in the high temperature sector,the measurement result front indicated attracts the mixed function to be possible enable the polycrystalline silicon youngest son life drop which the high temperature process creates to obtain the restoration.The good back surface field may enhance the battery obviously the open-circuit voltage.
d.silk-screen printing metal electrode
In the formalization production,crafts and so on silk-screen printing craft and vacuum evaporation,metal galvanization compares,has the superiority,in the present craft,the positive printing material selects generally including the silver pulp,Its primary cause is the silver has good conductive,the weldability and in the silicon low diffusivity.The conductive sea electric conductivity which after the silk-screen printing,the annealing form is decided by the pulp chemical composition,the vitreous body content,the silk screen thick brewer's grain,the sintering condition and silk screen thickness.80at the beginning of year,the silk-screen printing has some flaws,1) Like the grating width is big,usually is bigger than150microns;2)Creates the shade to be big,the battery packing factor is low;3)Does not suit the superficial deactivation,mainly is the surface diffusion density is high,otherwise the contact resistance is big.At present may the silk screen print out the line width with the advanced method to reach50microns gratings,thickness surpasses15microns,the block resistance for2.5~4mΩ;,this parameter may satisfy the highly effective battery the request.Some people made the solar cell on15×15square centimeter Mc-Si to the silk-screen printing electrode and the evaporation electrode to carry on the comparison,each parameter did not have the disparity nearly.
4concluding remark
The polytropism silicon cell manufacture craft forward developed unceasingly, had guaranteed the battery efficiency enhanced unceasingly,the cost dropped,along with to the material,component physics,optics characteristic understanding deepening,caused the battery the structure to hasten reasonably,the laboratory level and the industrialization big production distance reduced unceasingly.The silk-screen printing and buried the grid craft highly effective for,the low cost battery has played the main role,the highly effective Mc-Si battery module entered the market massively, the present research is devoting on the new thin film structure,the inexpensive substrate battery and so on,facing the user,the work which we needed to do is the realization mass,the low cost production,was willing us to achieve this goal even more diligently.
中文翻译
多晶硅太阳能电池制作工艺概述
众所周知，利用太阳能有许多优点，光伏发电将为人类提供主要的能源，但目前来讲，要使太阳能发电具有较大的市场，被广大的消费者接受，提高太阳电池的光电转换效率，降低生产成本应该是我们追求的最大目标，从目前国际太阳电池的发展过程可以看出其发展趋势为单晶硅、多晶硅、带状硅、薄膜材料（包括微晶硅基薄膜、化合物基薄膜及染料薄膜）。从工业化发展来看，重心已由单晶向多晶方向发展，主要原因为；[1]可供应太阳电池的头尾料愈来愈少；[2]对太阳电池来讲，方形基片更合算，通过浇铸法和直接凝固法所获得的多晶硅可直接获得方形材料；[3]多晶硅的生产工艺不断取得进展，全自动浇铸炉每生产周期（50小时）可生产200公斤以上的硅锭，晶粒的尺寸达到厘米级；[4]由于近十年单晶硅工艺的研究与发展很快，其中工艺也被应用于多晶硅电池的生产，例如选择腐蚀发射结、背表面场、腐蚀绒面、表面和体钝化、细金属栅电极，采用丝网印刷技术可使栅电极的宽度降低到50微米，高度达到15微米以上，快速热退火技术用于多晶硅的生产可大大缩短工艺时间，单片热工序时间可在一分钟之内完成，采用该工艺在100平方厘米的多晶硅片上作出的电池转换效率超过14％。据报道，目前在50～60微米多晶硅衬底上制作的电池效率超过16％。利用机械刻槽、丝网印刷技术在100平方厘米多晶上效率超过17％，无机械刻槽在同样面积上效率达到16％，采用埋栅结构，机械刻槽在130平方厘米的多晶上电池效率达到15.8％。
下面从两个方面对多晶硅电池的工艺技术进行讨论。
2.实验室高效电池工艺
实验室技术通常不考虑电池制作的成本和是否可以大规模化生产，仅仅研究达到最高效率的方法和途径，提供特定材料和工艺所能够达到的极限。
2.1关于光的吸收
对于光吸收主要是：
（1）降低表面反射；
（2）改变光在电池体内的路径；
（3）采用背面反射。
对于单晶硅，应用各向异性化学腐蚀的方法可在（100）表面制作金字塔状的绒面结构，降低表面光反射。但多晶硅晶向偏离（100）面，采用上面的方法无法作出均匀的绒面，目前采用下列方法:
[1]激光刻槽
用激光刻槽的方法可在多晶硅表面制作倒金字塔结构，在500～900nm光谱范围内，反射率为4～6％，与表面制作双层减反射膜相当。而在（100）面单晶硅化学制作绒面的反射率为11％。用激光制作绒面比在光滑面镀双层减反射膜层（ZnS/MgF2）电池的短路电流要提高4％左右，这主要是长波光（波长大于800nm）斜射进入电池的原因。激光制作绒面存在的问题是在刻蚀中，表面造成损伤同时引入一些杂质，要通过化学处理去除表面损伤层。该方法所作的太阳电池通常短路电流较高，但开路电压不太高，主要原因是电池表面积增加，引起复合电流提高。
[2]化学刻槽
应用掩膜（Si3N4或SiO2）各向同性腐蚀，腐蚀液可为酸性腐蚀液，也可为浓度较高的氢氧化钠或氢氧化钾溶液，该方法无法形成各向异性腐蚀所形成的那种尖锥状结构。据报道，该方法所形成的绒面对700～1030微米光谱范围有明显的减反射作用。但掩膜层一般要在较高的温度下形成，引起多晶硅材料性能下降，特别对质量较低的多晶材料，少子寿命缩短。应用该工艺在225cm2的多晶硅上所作电池的转换效率达到16.4%。掩膜层也可用丝网印刷的方法形成。
[3]反应离子腐蚀（RIE）
该方法为一种无掩膜腐蚀工艺，所形成的绒面反射率特别低，在450～1000微米光谱范围的反射率可小于2％。仅从光学的角度来看，是一种理想的方法，但存在的问题是硅表面损伤严重，电池的开路电压和填充因子出现下降。
[4]制作减反射膜层
对于高效太阳电池，最常用和最有效的方法是蒸镀ZnS/MgF2双层减反射膜，其最佳厚度取决于下面氧化层的厚度和电池表面的特征，例如，表面是光滑面还是绒面，减反射工艺也有蒸镀Ta2O5,PECVD沉积Si3N3等。ZnO导电膜也可作为减反材料。
2.2金属化技术
在高效电池的制作中，金属化电极必须与电池的设计参数，如表面掺杂浓度、PN结深，金属材料相匹配。实验室电池一般面积比较小（面积小于4cm2），所
以需要细金属栅线（小于10微米），一般采用的方法为光刻、电子束蒸发、电子镀。工业化大生产中也使用电镀工艺，但蒸发和光刻结合使用时，不属于低成本工艺技术。
电子束蒸发和电镀:
通常，应用正胶剥离工艺，蒸镀Ti/Pa/Ag多层金属电极，要减小金属电极所引起的串联电阻，往往需要金属层比较厚（8～10微米）。缺点是电子束蒸发造成硅表面/钝化层介面损伤，使表面复合提高，因此，工艺中，采用短时蒸发Ti/Pa层，在蒸发银层的工艺。另一个问题是金属与硅接触面较大时，必将导致少子复合速度提高。工艺中，采用了隧道结接触的方法，在硅和金属成间形成一个较薄的氧化层（一般厚度为20微米左右）应用功函数较低的金属(如钛等)可在硅表面感应一个稳定的电子积累层(也可引入固定正电荷加深反型)。另外一种方法是在钝化层上开出小窗口（小于2微米），再淀积较宽的金属栅线（通常为10微米），形成mushroom—like状电极，用该方法在4cm2Mc-Si上电池的转换效率达到17.3％。目前，在机械刻槽表面也运用了Shallow angle(oblique)技术。
2.3PN结的形成技术
[1]发射区形成和磷吸杂
对于高效太阳能电池，发射区的形成一般采用选择扩散，在金属电极下方形成重杂质区域而在电极间实现浅浓度扩散，发射区的浅浓度扩散即增强了电池对蓝光的响应，又使硅表面易于钝化。扩散的方法有两步扩散工艺、扩散加腐蚀工艺和掩埋扩散工艺。目前采用选择扩散，15×15cm2电池转换效率达到16.4%，n++、n+区域的表面方块电阻分别为20Ω和80Ω.
对于Mc—Si材料，扩磷吸杂对电池的影响得到广泛的研究，较长时间的磷吸杂过程（一般3～4小时），可使一些Mc—Si的少子扩散长度提高两个数量级。在对衬底浓度对吸杂效应的研究中发现，即便对高浓度的衬第材料，经吸杂也能够获得较大的少子扩散长度（大于200微米），电池的开路电压大于638mv,转换效率超过17％。
[2]背表面场的形成及铝吸杂技术
在Mc—Si电池中，背p+p结由均匀扩散铝或硼形成，硼源一般为BN、BBr、APCVD SiO2：B2O8等，铝扩散为蒸发或丝网印刷铝，800度下烧结所完成，对铝吸杂的作用也开展了大量的研究，与磷扩散吸杂不同，铝吸杂在相对较低的温度下进行。其中体缺陷也参与了杂质的溶解和沉积，而在较高温度下，沉积的杂
质易于溶解进入硅中，对Mc—Si产生不利的影响。到目前为至，区域背场已应用于单晶硅电池工艺中，但在多晶硅中，还是应用全铝背表面场结构。
[3]双面Mc—Si电池
Mc—Si双面电池其正面为常规结构，背面为N＋和P＋相互交叉的结构，这样，正面光照产生的但位于背面附近的光生少子可由背电极有效吸收。背电极作为对正面电极的有效补充，也作为一个独立的栽流子收集器对背面光照和散射光产生作用，据报道，在AM1.5条件下，转换效率超过19％。
2.4表面和体钝化技术
对于Mc—Si，因存在较高的晶界、点缺陷（空位、填隙原子、金属杂质、氧、氮及他们的复合物）对材料表面和体内缺陷的钝化尤为重要，除前面提到的吸杂技术外，钝化工艺有多种方法，通过热氧化使硅悬挂键饱和是一种比较常用的方法，可使Si-SiO2界面的复合速度大大下降，其钝化效果取决于发射区的表面浓度、界面态密度和电子、空穴的浮获截面。在氢气氛中退火可使钝化效果更加明显。采用PECVD淀积氮化硅近期正面十分有效，因为在成膜的过程中具有加氢的效果。该工艺也可应用于规模化生产中。应用Remote PECVD Si3N4可使表面复合速度小于20cm/s。
3工业化电池工艺
太阳电池从研究室走向工厂，实验研究走向规模化生产是其发展的道路，所以能够达到工业化生产的特征应该是：
[1]电池的制作工艺能够满足流水线作业；
[2]能够大规模、现代化生产；
[3]达到高效、低成本。
当然，其主要目标是降低太阳电池的生产成本。目前多晶硅电池的主要发展方向朝着大面积、薄衬底。例如，市场上可见到125×125mm2、150×150mm2甚至更大规模的单片电池，厚度从原来的300微米减小到目前的250、200及200微米以下。效率得到大幅度的提高。日本京磁（Kyocera）公司150×150的电池小批量生产的光电转换效率达到17.1%，该公司1998年的生产量达到25.4MW。
（1）丝网印刷及其相关技术
（2）多晶硅电池的规模化生产中广泛使用了丝网印刷工艺，该工艺可用于扩散源的印刷、正面金属电极、背接触电极，减反射膜层等，随着丝网材料的改
善和工艺水平的提高，丝网印刷工艺在太阳电池的生产中将会得到更加普遍的应用。
a.发射区的形成
利用丝网印刷形成PN结，代替常规的管式炉扩散工艺。一般在多晶硅的正面印刷含磷的浆料、在反面印刷含铝的金属浆料。印刷完成后，扩散可在网带炉中完成（通常温度在900度），这样，印刷、烘干、扩散可形成连续性生产。丝网印刷扩散技术所形成的发射区通常表面浓度比较高，则表面光生载流子复合较大，为了克服这一缺点，工艺上采用了下面的选择发射区工艺技术，使电池的转换效率得到进一步的提高。
b.选择发射区工艺
在多晶硅电池的扩散工艺中，选择发射区技术分为局部腐蚀或两步扩散法。局部腐蚀为用干法（例如反应离子腐蚀）或化学腐蚀的方法，将金属电极之间区域的重扩散层腐蚀掉。最初，Solarex应用反应离子腐蚀的方法在同一台设备中，先用大反应功率腐蚀掉金属电极间的重掺杂层，再用小功率沉积一层氮化硅薄膜，该膜层发挥减反射和电池表面钝化的双重作用。在100cm2的多晶上作出转换效率超过13％的电池。在同样面积上，应用两部扩散法，未作机械绒面的情况下转换效率达到16％。
c.背表面场的形成
背PN结通常由丝网印刷A浆料并在网带炉中热退火后形成，该工艺在形成背表面结的同时，对多晶硅中的杂质具有良好的吸除作用，铝吸杂过程一般在高温区段完成，测量结果表明吸杂作用可使前道高温过程所造成的多晶硅少子寿命的下降得到恢复。良好的背表面场可明显地提高电池的开路电压。
d.丝网印刷金属电极
在规模化生产中，丝网印刷工艺与真空蒸发、金属电镀等工艺相比，更具有优势，在目前的工艺中，正面的印刷材料普遍选用含银的浆料，其主要原因是银具有良好的导电性、可焊性和在硅中的低扩散性能。经丝网印刷、退火所形成的金属层的导电性能取决于浆料的化学成份、玻璃体的含量、丝网的粗糟度、烧结条件和丝网版的厚度。八十年度初，丝网印刷具有一些缺陷，ⅰ)如栅线宽度较大，通常大于150微米；ⅱ)造成遮光较大，电池填充因子较低；ⅲ)不适合表面钝化，主要是表面扩散浓度较高，否则接触电阻较大。目前用先进的方法可丝网印出线宽达50微米的栅线，厚度超过15微米，方块电阻为2.5~4mΩ，该参数可
满足高效电池的要求。有人在15×15平方厘米的Mc—Si上对丝网印刷电极和蒸发电极所作太阳电池进行了比较，各项参数几乎没有差距。
4结束语
多晶硅电池的制作工艺不断向前发展，保证了电池的效率不断提高，成本下降，随着对材料、器件物理、光学特性认识的加深，导致电池的结构更趋合理，实验室水平和工业化大生产的距离不断缩小。丝网印刷和埋栅工艺为高效、低成本电池发挥了主要作用，高效Mc—Si电池组件已大量进入市场，目前的研究正致力于新性薄膜结构、廉价衬底上的电池等，面对用户，我们需要作的工作是实现更大批量的、低成本的生产，愿我们更加努力实现这一目标。