Transcript 4. 太陽能工程-第四章

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Chapter 4 - variety of solar cells
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Chapter 4 - variety of solar cells
4-1 單晶矽太陽電池(single crystal Si)
Bulk, wafer type
4-2 多晶矽太陽電池(poly crystal Si)
Wafer type
4-3 非晶矽太陽電池(amorphous Si)
Thin film type
4-4 化合物半導體太陽電池
Compound semiconductor
4-5 其他太陽電池 (Other solar cells)
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4-1 single crystal silicon solar cells
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4-1 single crystal silicon solar cells
4-1-1 Summary
4-1-2 Structure
4-1-3 Single crystal silicon solar cell production method
4-1-4 High efficiency of single crystal silicon solar cells
4-1-5 High efficiency single crystalline silicon solar cells
4-1-6 Future topics
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4-1-1 Summary
Solar cells materials can be divided into silicon Department,
Department of compound semiconductors and other Three
types. Most of the practical use of solar cells Si Department
,crystal structure is subdivided into single crystal,
Polycrystalline and amorphous threetypes.
Species
晶矽
Crystalline
Semiconductor materials
市場模組發
電轉換效率
單晶矽
Single Crystalline
12~20%
多晶矽
Poly Crystalline
10~18%
非晶矽
Si、SiC、SiGe、SiH、SiO
6~9%
Amorphous
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Single-crystal silicon solar cell characteristics
(1) The low density of sunlight, so the practical needs of large
area solar cells, coupled with the Si material itself is very
low impact on the environment.
(2) Production techniques and by single crystal manufacturing
technology pn junction Si integrated circuits technology for
electronics, with the maturity of the technology improved by
leaps and bounds.
(3) Si of low density, lightweight material.In particular, very strong
on the correspond, even if the thickness of the sheet of less
than 50μm,the intensity is enough.
(4) Its high conversion efficiency of polycrystalline silicon and
amorphous silicon solar cells.
(5) Power generation characteristics and stability.
(6) Order construct indirect migratory sunlight absorption coefficient is only
103cm-1, is quite small. Therefore, absorption of the solar spectrum needs
a 100μm thick silicon.
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4-1-2 構造 – (1) 基本構造
• 單晶矽太陽電池之基本電池結構顯示在圖4-1。使用的基
板，p型或n型皆可以，然而因p型中之電子少數擔體之擴
散距離比n型中之少數擔體之電洞要長，故為了加大光電
流，一般使用p型。
圖4-1 單晶矽
太陽電池構造
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光起電力效果之少數載體效應
depletion region in PN junction
n
p
接合
光
Lp
Xj
Ln
由圖4-2所示，因光照射所
生之電子與電洞中的少數
擔體(p型為電子，n型為電
洞)，因擴散而向接合部移
動。
Minority carriers (generated
from p layer) extracted to
n layer side
圖4-2 光起電力效果之少數載體效應
(Xj為接合深度，Ln、Lp為電子與電洞之擴散長度)
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(2) 淺接合構造
短波長的光，由於半導體的光吸收係數很大，故在表面
被吸收而生成電子-電洞對。若接合太深時，則使得在表
面生成之少數擔體不易到達，再加上表面之再結合速度
大時，生成之電子-電洞對因而消滅，更使到達接合處之
少數擔體降低。
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(3) BSF(Back Surface Field)構造
如圖4-3所示點線部分，n+p
之接合電池中厚度為100μm
以上的效率一定，不需要較
大厚度。為了薄膜化而在少
數擔體的擴散距離內附加表
面電極，使應轉化的光電流
之少數擔體，因在電極部份
再結合而被消滅
圖4-3 BSF構造的依存效果
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含有BSF構造之太陽電池能階模式
Ec導電帶
EF費米階位準
Ev價電子帶
n+
p
為了避免光電流減少及轉
換效率降低，故在裏面電
極近旁形成p+層而有n+pp+
構造如圖4-4所示能階帶
圖，在裏面pp+層間之費
米準位差而形成電場(能
障)，此稱為BSF構造
P+
圖4-4 含有BSF構造之
太陽電池能階模式
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2. 電極構造
電極功用是將電池所產生之電力以最少損失取出，因此希
望有良好的毆姆性接觸、低的串聯電阻、接著強度高、焊
接性良好。代表的電極樣式在圖4-5顯示，Finger寬度(間隙):
75μm(2mm)，127μm(4mm)，Bus bar之寬度 (數目):1mm(4)
，0.25mm(4)。電極所占之面積一般在5~7%。
圖4-5 典型電極樣式(細線為Finger
，白色中空線為Bus Bar粗線為帶狀電極)
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BSR構造
圖4-6 BSR (Back surface reflector)構造。活用在裏面光反
射，而使在入射光路上未被Si所充分吸收，可在反射光路
上被吸收，以增加光電流。
反射防止膜
表面電極
n+
p
p+
裏面電極
BSF
裏面反射膜(Al或Au)
圖4-6 BSR構造(附BSF構造)
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3. 封存光之構造 (Light trapping)
(1)By anti-reflection film
(2)By texture surface or roughness
(1) 反射防止膜-1 (anti-reflection film)
為了減少反射損失，使用折射率不同之透明材料作成反
射防止膜。
λ=4nd，n2=nsi no
AR film折射率 n
Si之折射率為nsi
厚度 d
環境之折射率(air) no
入射光之波長incident wavelength λ
no = 1
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(1) 反射防止膜-2
圖4-7以實線表示Si之反射特性與施 (1)
以折射率為2.25時之反射防止膜
(2)
ITO
N-type Si
P-type Si
Al
(3)
(4)
ITO
N-type Si
P-type Si
Al
圖4-7 Si的反射特性(1)鏡面Si (2)鏡面Si+反射防止膜
(3)Texture處理後的Si (4)Texture處理+反射防止膜
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(2)組織(Texture)構造-粗糙化(texture, roughness)
by etching on the Si surface
如圖4-8示，在Si(100)面上以侵蝕液所形成之(111)面微
小四面體之金字塔群所構成的組織構造上，再某一金字
塔面上向下方反射之光，可活用為其他的金字塔中進入
之多重反射。就全體而言，可減少反射。特別是進入Si
內光受到折射。
Refractive, reflection
圖4-8 Texture構造的概念
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4-1-3 單晶矽太陽電池之製作法
大體而言，分為基板用晶圓(wafer)製作過程及電池(cell)製
作過程。在此，因晶圓之製作過程與太陽電池無直接關
係，故僅止於概說，論述重點放在單晶矽太陽電池特有之
電池製作過程。
硅石
SiO2
金屬級Si
矽烷氣體
多晶矽
單晶矽
切割
反射防止膜
電池
Texture處裡
研磨.蝕刻
接合成形
電極成形
圖4-9 單晶矽太陽電池之製作流程
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(1) 氣體擴散法
此為將欲添加之不純物以氣體狀送入保持在高溫之基板
上，將P當做不純物擴散至p型Si上，形成n型者較常使
用。擴散源以P2O5(固體)，POCl4(液)及PH3(氣)較常使用
，將Si保持在850~950度而擴散
，此時Si內之不純物濃物N(χ)
，以表面密度為定常狀態(N0)而
解擴散方程式。
D 為不純物之擴散常數為溫度函數
t 為擴散需要時間
圖4-10 因擴散法所致
不純物分佈圖
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2


 No 
x


N ( x)  
 exp 


4
Dt

Dt




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(2) 固相擴散法
此為在基板表面堆積含有不純物之擴散劑，而後在高溫
下將不純物導入內部之方法。此時因表面之不純物密度
總量的一定。故得高斯分佈

N ( x)  

2


No 
x


 exp 
 Dt   4 Dt 
此不純物分佈在圖4-10中以點線表示。
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(3) 離子注入法
不純物分N(χ)依高斯分佈
2

 No 


x

R


N ( x)  
 exp

2
 2  

2 


N0為注入離子之劑量(dose)
R為投影飛程(分佈的peak位置)
σ為分佈之標準偏差
這些都由離子種及注入能量來決定。圖4-11為其不純物分佈例。
圖4-11 離子注入法所致不純物分佈
(R為投影飛程，為標準偏差，No為Dose量)
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BSR構造：
將n+p太陽電池之電池裏面做成鏡面，以蒸著法堆積如Al
之金屬。與Al來比較，使用Au、Ag及Cu在太陽電池裏
面之反射相當好，故長波長(1.0~2.5μm)區域中，從太
陽電池之表面往外面逃出之光很多，達到BSR效果。
圖4-12表示BSR構造之效果
圖4-12 BSR構造的效果
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4. 光封存構造成形法
(1) 反射防止膜
使用於反射防止膜之材料的折射率列於表4-1。1層之反
射防止膜以折射率1.8~1.9之SiO最常使用。此外，CeO2
、Al2O3、Si3N4、SiO2及SiO2-TiO2也常使用。2層反射
防止膜時，使用TiO2與Ta2O5等折射率大之材料。
材料
折射率
SiO2
1.44
MgF2
1.44
SiO2-TiO2 1.80~1.96
Al2O3
1.86
CeO2
1.90
材料
折射率
SiO
SnO2
Si3N4
Ta2O5
TiO2
1.80~1.90
2.00
2.00
2.20~2.26
2.30
表4-1 各種材料的折射率
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(2) 組織構造
前述之Si(100)面上，以侵蝕所形成之(111)面金字塔構
造，為利用Hydrazine 60%溶液，於110度保持10分時
間，或1%NaOH水溶液，保持在沸騰狀態5分鐘後可得
。模型圖如圖4-13所示。
圖4-13 Texture構造的模型圖
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4-1-4 單晶矽太陽電池之高效率化
1. 理論效率
太陽電池之能源轉換效率η，由電池之最大出電力Pm
及全體太陽光譜之光入力比所決定
Pm Im Vm IscVocFF



Pin
Pin
Pin
Im、Vm為最大電力之電流與電壓，Isc、Voc、FF
為短路電流，開放電壓及曲線因子(填充因子)。
FF=(ImVm) / (IscVoc)
Fill Factor
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太陽電池的光照射特性
圖4-14為太陽電池
光照射時之出力特
性圖，與性能有關
者為Isc、Voc及FF
三個量。
圖4-14 太陽電池的光照射特性
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2. 高效率化基本考量
現實太陽電池有以下之各項損失因素：
(1) 反射損失：半導體表面之反射，使太陽光無法全部進
入而產生之損失，使用反射防止膜及組織構造可改善
(2) 透過損失：能量比禁制帶寬小之光子，不被半導體吸
收而透過，沒有被能量轉換，造成光電能源轉換之損
失結果。可被自由擔體吸收而存在。
(3) 光能之不完全利用損失：被半導體所吸收之光子，若
其能量大於禁制帶寬時，能量被半導體之結晶格子吸
收轉成熱而消失。
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(4) 再結合損失：生成之電子與正孔在表面或半導體內
再結合，則不產生光電流。
(5) 電壓因子損失：利用p-n接合時，最大可取得之電壓
為擴散電位，通常費米準位存在於禁制帶寬內，故
在相當於禁制帶寬之電壓以下。亦即，開放電壓較
低而造成損失。
(6) 曲線因子損失：半導體之電阻不為零及歐姆性接觸
部位之電阻為串聯電阻，此外理想之p-n接合沒有洩
漏電流。而現實上因為漏洩電流，使p-n接合上有並
聯電阻出現。故此項包含串聯及並聯電阻損失。
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氧化物誘起之HL接合
圖4-16所示，不以不純
物添加方式製作n+層
，而以堆積內藏空間電
荷之氧化膜，在氧化膜
與n型之間蓄積電子，
形成看起來為n+n之HL
接合，可將開放電壓改
善由634mV(AM-1，25
度)，改善成642mV
圖4-16 氧化物誘起之HL接合 (AM-0，25度)
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NINP構造太陽電池
使用氧化膜進行表面披覆，降低表面再結合之提案也
有，以增加開放電壓之MINP(Metal insulator，np)構造
，如圖4-17(a)所示，可大幅增加Voc值。圖4-17(b)在光
電流的收集電極部上，金屬與半導體直接接觸，再結
合電流，對暗時的逆方向飽和電流有很大影響。
圖4-17 NINP構造太陽電池
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4-1-5 高效率單結晶矽太陽電池
1. 平面型太陽電池 - (1) PESC
圖4-18顯示PESC構造(passivated emitter solar cell)，基
本上與MINP構造電池類似，但表面電極部的構造不
同，使用添加B之FZ-Si當做基板，可在減少逆飽和電
流，在體積內之再結合，同時活用少數擔體為，增大
反射防止膜
表面電極
光電流。
極薄酸化膜
n
P
裏面電極
圖4-18 PESC之構造
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(1) PESC
因金屬電極與n+-Si間有極薄之絕緣膜，故光電流在此
部份不用Tunnel效果通過不行。為避免這些因素，將
金屬電極與n+-Si層之直接接觸部限制在微小領域內，
可減低逆方向飽和電流，並增加光電流收集率。
在反射防止膜上與MINP電池同樣，採用ZnS與MgF2
之2層構造。以此電池，在AM-1.5,100mW/cm2。
28度之條件下，η=19.0~19.1%。再改良製程可達到
Jsc=36.5mA/cm2，Voc=662mV，FF=0.819，η=19.8%
，轉換效率20%之目標也已接近。
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(2) μg PESC
基本上與上述的PESC構造相同。
1.微細構造將表面之光反射從3~4%降至1%以下。
2.光斜線至Si表面，即使在某一面被反射也可能入射至
某一菱面，可增加光吸收量。換算成光生成擔體被收
集時之擴散距離，也有35%。
3.使用photolithography
工程與Texture構造比
較，再現性好。
圖4-19 μg PESC構造
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(3) PERC(passivated emitter rear cell)電池
太陽電池裡面passivation之重要性的PERC構造畫在圖420。在表面及裡面以SiO2膜做passivation，且在表面上形
成逆轉型金字塔構造，可減少表面反射。AM-1.5，25度
時，可達成Jsc=40.3mA/cm2，Voc=696mV，FF=0.814，
η=22.8%之效果。
圖4-20 PERC之構造
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(4) PERL(Passivated emitter rear rocally diffused)
PERC可降體積內，表面及裡面之再結合速度，增加Voc
及Jsc是成功的。如圖4-21所示，裡面電極為局部的，以
B之擴散形成PERL構造。
可達成AM-1.5，25度下，Jsc=42.9mA/cm2，Voc=696mV
，FF=0.81，η=24.2%之高效率。
圖4-21
PERL太陽電池構造
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(5) 電極埋入式太陽電池
圖4-22所示為埋入式電極(burried contact)之高效率太陽電
池，此太陽電池之製作工程步驟少即可成之。做成金字
塔式之Texture構造，以擴散接合形成後，做表面氧化。
以雷射鑽頭將氧化膜及擴散層刺穿，在深度40μm切成
20μm之溝。AM-1.5，100mW，28度之轉換效率
18.6%(Jsc=38.0mA/cm2，Voc=609mV，FF=0.802)
圖4-22
埋入式電極太陽電極構造
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2. 大面積太陽電池
目前10×10cm2大面積之太陽電池已近實用化，通常太陽電
池面積增大時效率會降低，其理由為下述:
(1)所給與之表面電極樣式，當太陽電池面積增大時電極部
之電阻也增加。
(2)某些材料之材質不均一時，當面積增加，含有壞材料之
比率也增大。
(3)高效率、大面積特點為:使用高品質單晶矽太陽電池，
其高效率、小面積之製作技術若適用大面積時，性能之
低下不多。
(4)模組效率改善:用此大面積太陽電池，75.2Wp之模組，
電池效率16.9%，模組效率15.2%。
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3. 集光型太陽電池
若不用排列式太陽電池，而已集光鏡或集光透鏡收集
入射光，以少數之電池來發電時，電池成本轉為集光
器、支持台、追尾裝置之成本，全體而言應該降低。
但集光用電池之效率不高，對整體系統而言沒什麼優
點。電池效率隨集光比之增加而增加，但若溫度也隨
之上升時，則效率降低。隨集光比之增加，轉換效率
η亦隨開放電壓Voc對數比例增加，但因Voc在p-n接合
之擴散電位近值上飽和，故η無法無限制增加。
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(1) 點接觸型
AM-1.5，100mW/cm2，
24度時，Jsc=41.5mA/cm2
，Voc=582mV，FF=0.786
，η=22.2%
圖4-23
點接觸型太陽電池構造
• 高品質，高電阻基板(FZ-Si，
電阻390Ω cm，少數擔体
壽命1ms)之利用。
• 以氧化膜(厚度120nm)
passivation使表面結合速度降低。
• 裏面使擴散區域最小，使金屬
與半導體之直接接觸區域
限制在最小(10×10μm，50μm)
間隔，故在結合性低。
• 薄膜(厚度112,152μm)上之具
BSR效果
• 表面Texture之利用
• 解除p-n兩電極在裡面之電極陰
影損失
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(2) 微細溝型(micro groove)
圖4-24 集光用μg PESC構造
AM-1.5，100mW/cm2，28
度時，Jsc=40.2mA/cm2，
Voc=653mV，FF=0.829 ，
η=21.8%
基本上與前述之μg PESC類似，但表面的Finger電極
不同。基板為0.1，0.2Ω cm之FZ-Si。 其特徵:
1.薄氧化膜passivation。
2.對表面擴散層之金屬電極接觸面積變小(0.18mm2)。
3.使用V溝之斜面降低表面反射及增加光的取得。
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Prismatic Cover之原理
圖4-25
Prismatic Cover之原理
圖4-25所示，將prismatic(菱
鏡)被覆之周期與Finger電
極之周期配合，可使光從
電極部分避開，入射至沒
有電極之部分。因高集光
下活性區域之轉換效率支
配特性是重要因素，故不
用裏面有二電極之太陽電
池也可。
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4-1-6 今後的課題
• 現在單結晶矽太陽電池之實用化已達10×10cm2規格。轉換
效率也高，潮流動向以目前之製作法可提高效率及降低成
本至多少，雖然沒做詳細檢討，但以模組化效率增加為今
後最大課題。
• 短波長光之利用為經常課題，但對單晶矽而言，尚無可用
之提案。雖然採用寬間隙半導體與單晶矽所形成積層構造，
做為太陽電池之基波或可為此範圍，但更不同之提案，如
導入色素增加矽中之短波長光轉換，可能有較高效率。
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4-2 多晶矽太陽電池
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4-2 多晶矽太陽電池
4-2-1
4-2-2
4-2-3
4-2-4
4-2-5
多晶矽材料之形成
結晶粒界之電氣特性及不活性化
接合構造及理論效率
太陽電池製造技術
將來展望
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4-2 多晶矽太陽電池
本節中所述多晶矽電池是以降低成本為第一要務，效率
為第二而開發出之太陽電池。
矽太陽電池，材料之光吸收係數小，為膜化可能減少光
電流，得不到高效率，故不受重視。但若能將光封存在
吸收層內，則薄膜也得到高光電流，而且也有暗電流之
減少效果，在理論上也可達到高效率。薄膜且能吸收光
者不一定為單晶，非晶矽為最佳例子。
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4-2-1 多晶矽材料之形成
多晶矽太陽電池是將原材料價格中之結晶化部份盡量降
低，以降低Si電池之價格。單晶基板價格中，可以降低
成本之部分，可分為:
(1)原材料純度可降低至何種程度。
(2)含結晶化等之基板製造能源可降低至何種程度。
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矽中金屬不純物及其大略容許量
矽材料為(1)金屬級矽(不純物濃度10-2左右)，含有許多製
造深準位之重金屬，亦稱Life time killer，Donor及Acceptor
之製造元素以及大量之氧氣、炭等。代表性不純物表示於
表4-2。 不純物
矽中金屬(p.p.m) 容許量(p.p.m)
Dopant
Al
B
P
1500~4000
40~80
20~50
Life time
killer
Ti
V
Fe
Cr
Ni
160~250
80~200
2000~3000
50~200
30~90
0.001
0.002
0.02
0.1
0.8
表4-2 矽中金屬不純物及其大略容許量
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轉換效率的結晶粒徑依存性
圖4-26為結晶粒徑與理論效
率之考察結果。轉換效率之
絕對值與材料之品質有很強
的依存關係，且與光及擔體
之封存亦有關係，上述計算
並不考慮這些因素，比目前
實用化之效率值還低，但厚
膜之矽太陽電池，需要
圖4-26 轉換效率的結晶粒徑依存性
50μm以上之結晶粒徑要
(實線虛線各為無光封存
，載體封存效果之理論值) 求。
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液相矽基板製造法
製作半導體結晶之方法可分為液相成長法與氣相法兩
種，圖4-27為製造太陽電池用矽基板之液相法。
圖4-27 液相矽基板製造法
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Silso製造裝置概略圖
Silso之結晶成長裝置，如
圖4-28，太陽電池用晶圓
之數mm以上結晶粒徑需
求。
圖4-28 Silso製造裝置概略圖
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電磁鑄造法之理論圖
以連續供給原料方式製
長型Ingot之電磁鑄造法
，來得到多晶Ingot也被
開發。其太陽電池效率
亦高，電磁鑄造法之概
略如圖4-29所示。
圖4-29 電磁鑄造法之理論圖
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S-Wed法原理
石墨與矽之溼洞性佳，雖然可與Si形成部分SiC，但常用
來製作多晶矽板。如利用網狀石墨片來製作矽膜之S-Wed
法(supported wed)，示於圖4-30。速度超過1000cm2/min，
效率為12%。
圖4-30 S-Wed法原理
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SCIM(silicon coating by inverted meniscus)法
陶瓷表面、凹凸不平，也
可能放出不純物，使用需
注意，使用陶瓷當做基板
之技術，如SCIM，表示
於圖4-31，0.3mm厚之Si
以60cm2/min之速度生成。
圖4-31 SCIM法在陶瓷基板
上矽膜之成長模式
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RAFT(ramp assissted foil casting)法原理
由液相成長Si後再利用基板
者，如RAFT法，示於
圖4-32。在被稱ramp以溶融
石墨炭所被覆之石墨製基板
上，讓Si成長後因熱膨脹係
數之不同而剝離得到板狀Si
。0.3mm之厚度成長速度可
達18000cm2/min。
圖4-32 RAFT法原理
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Cast Ribbon法制備矽薄板
在鑄造及片狀法之技術上，有利用片狀之Cavity回收容
器中注入熔融矽，以製作片狀Si晶圓稱為Cast Ribbon法
。雖為鑄造法，但無Ingot製作之高速切割問題及切片損
失，是一有力之製
作法。其原理示於
圖4-33。
圖4-33 以Cast Ribbon法制備矽薄板概念圖
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4-2-2 結晶粒界之電氣特性及不活性化
1. 結晶粒界的物性及光電特性
圖4-34為結晶粒界附近之能階帶，以荷電狀態分類各別之
樣式。此圖對n型半導體所示之樣式，對p型也一樣。對n
型半導體而言，結晶粒界帶負電，其分佈為比禁制帶中的
中央部位還高。
圖4-34 由結晶粒界之電子狀態所形成
之三種典型能階樣式
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2. 粒界的特性評估法
為了達到高效率化之多晶矽，基本上必須降低結晶粒界
的電氣活性度，因此如何掌握它的特性是非常重要的。
特性評估法，常用的如表4-3所示。
手法
結晶學的評估
具體分析技術
1.Decoration法
2.X- ray Topography
3.選擇蝕刻法
電子線利用手法
1.走查型Auger分析(SAM)
2.電子線Probe微小分析(EPMA)
3.電子線激起電流像法(EBIC)
光學的手法
1.雷射光激起電流像法(LBIC)
2.單色光激起電流像法(MBIC)
表4-3 結晶粒界的特性評估法
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單色光勵起電流像法(Monochromatic-light
beam induced current，MBIC)
圖4-35為在橫切結晶粒界之方向上，使用光束走查一次
所觀測之光電流分佈例，圖中虛線所示為理論值。
圖4-35 以MBIC觀察橫切結晶粒界
部份之光電分怖
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4-2-3 接合構造及理論效率
1. 多晶太陽電池作動之理論解析
多晶矽太陽電池特性，與單晶矽不同者如
(1)存在有結晶粒界、整體體積之特性，亦受到結晶粒界
近旁之少數擔體再結合特性之影響
(2)當多數擔體橫切流過結晶粒界時，有必要超過粒界所
生成之能階位障，影響串聯電阻
(3)結晶粒界之障礙高度由光照射可變化
(4)因長晶速度快，故體積內遍佈缺陷，擔體之擴散長度
較短等四點。
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結晶粒界考量
考慮多晶矽太陽電池之作動時，結晶粒界必須考慮下述
三種情況:
(1)結晶粒界對少數擔體之影響，要用那個物性值來表述
(2)結晶粒界若切過空乏層時之影響，用那個物性評估
(3)光照射時及暗狀態時，結晶粒界之特性如何變化
1
fil
1

 D
2
2A
2

S 1
 
fil A g
1
g
長為A之正方形結晶粒
再結合速度 S
減衰常數為fil
g代表結晶粒夠大
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結晶粒界的電荷狀態與太陽電池特性
依表4-4有9種組合存
在。在基材區域內粒
界在反轉層之狀態7~
9之構成上，光生成
擔體被粒界所吸入，
再結合損失變大，造
成光電流降低。
構
成
1
2
3
4
5
6
7
8
9
Base
粒
內
p
p
p
Emitter
粒
界
p+
p-
n
粒
內
n
n
n
可預期特性
粒
界
n+
低Voc
n-
最佳
p
低Voc
n+
佳
n-
佳
p
低Voc
n+
低Jsc
n-
低Jsc
p
低Jsc
表4-4 結晶粒界的電荷狀態與太陽電池特性
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高效率之結晶粒界的電荷狀態
狀態2之構成，其接合之能階梯式圖描繪於圖4-36上
圖4-36 可期待高效率之結晶粒界的電荷狀態
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2. 光封存及擔體(載子,carrier)封存
光
接合
Si
α
(a)傾斜裏面構造
Si
透明基板
如圖4-37將表面與裏面
做成非平行，則光可通
過複雜之通路經過半導
體而被吸收，實際上也
達到厚膜之效果，此即
薄膜太陽電池之光封存
效果。
(b)裏面Texture構造
圖4-37 光封存構造
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3. 各種高效率太陽電池構造
(1) 多晶厚膜電池
元件構造
開放端電壓 短路光電流 曲線率 轉換效率 受光面積
(mV)
(mA/cm2)
(%)
(%)
(cm2)
厚 機械V溝構造
膜 3電極
BSNSC
Cast Ribbon
601
611
611
596
36.5
35.4
35.4
37.4
77.8
75.9
75.9
75.4
17.1
16.4
16.4
16.8
100
100
125
100
薄 陶瓷基板
膜 金屬級Si基板
593
608
32.4
30.0
74.0
781
14.2
14.2
0.98
100
表4-5 多結晶矽太陽電池的出力特性
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機械的V溝構造電池模式圖
如圖4-38，pitch 70μm，深70μm之溝製成後，以酸或
鹼之侵蝕將受損層拿掉，並將溝整型。
圖4-38 機械的V溝構造電池模式圖
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3電極Bifacial電池之構造
3電極所示之構造，則不止
在表面，裏面也有收集電
子之電極存在，使得再由
裏面附近生成之電子能有
效的收集，且以Texture
etching，由裏面做氫化及
絕緣膜做不活性化所得之
元件。
圖4-39 3電極Bifacial電池之構造
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BSNSC之構造
而BSNSC之構造，為使表面不活性化，在表面皆用Si3N4
披覆。氮化膜以SiH4或NH3氣體用plasmaCVD法來製備。
因堆積時有多量的氫氣電漿存在多晶基板上，故氫氣不活
性化同時也存在。
圖4-40 BSNSC之構造
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圖4-41 典型的厚膜多晶矽太陽電池製程
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4-3 非晶矽太陽電池
amorphous Si
微晶矽
micro crystal Si
μc-Si
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4-3 非晶系太陽電池 amorphous Si
4-3-1
4-3-2
4-3-3
4-3-4
4-3-5
4-3-6
conspectus
Preparation and properties of amorphoussilicon
Solar cell structure and preparation process
Solar cells for moving characteristics
High-efficiency technology
Stability and reliability
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4-3-1 conspectus
PECVD: plasma enhanced chemical vapor deposition
Amorphous solar cells dates back to the early 1970s, to
the plasma CVD method , SiH4 gas preparation of amorphous
silicon film, visible light, has a large absorption coefficient, and
excellent light transmission characteristics.
SiH4 the plasma CVD method, system of a si (amorphous silicon),
containing 10 ~ 20% atomic hydrogen can reduce the structural
defects, resulting in excellent optical and electrical properties
and valence electron control nature. of a-Si: H by using the
fluorine iscalled a-Si: F, but is not widely available, so this
section follows the a-Si: H, referred to the a-Si.
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Amorphous silicon solar cell conversion
efficiency changes
Tandem
The chart below of a-Si solar cell
conversion efficiency increases and
its related technologies. Single
combination of the structure, the
photocurrent generation of a-Si layer
of the pin junction structure. Some of
the design for the incident photon to try
to imprt i-typ a-Si layer, or sequestration,
absorbing the body of the bear collection
to the electrode.
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4-3-2 Preparation and properties
of amorphous silicon
1. Thin film deposition method
a-Si and its alloys is based on the plasma CVD, thermal CVD,
reactive Sputtering method or optical CVD method, vapor-phase
syntheis is method to prepare thin films. Solar cells with a-Si plasma
of CVD method to prepare,it is the first production method described,
followed by optical CVD method, Doping.
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(1) Plasma Enhanced Chemical Vapor Deposition
(PECVD)法
As shown the generated SiHx (x ≦ 3)
response (neutral andionic).These
reactions are diffusion to reach 100
to 300 。C substrate, on which a variety
of reactions (adsorption, detachment ,
pulled out, insert and surface diffusion
process), the formation of a-Si film.
圖4-43 電漿CVD法材料氣體
至成膜之個種形成
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Capacity bound Plasma Enhanced CVD
(PECVD) device concept
Figure opposite electrode of the one electrode, Blocking capacity,
power Integrator with high frequency power supply connected to the
other electrode and the reactor when the ground. The poor quality
of the plasma in the electronic and ionic phase of the plasma
electrode (wall), and negative potential on the plasma in terms
of showing.
13.56 MHz
60 MHz
圖4-44 容量結合型Plasma CVD裝置概念
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(1) Structure and electronic state
Have long-range order of amorphous semiconductor material , although there
is no crystallization However, the chemical combination of atoms around
the state , may be considered for the crystallization of the same state.
But the combination of angle and combined with the close construct the
entropy of the length to and the dihedral angle of the middle distance
construct bias, making the crystallization on the sharp, level side, the
performance shown in figure crony style exists in the band gap.
Figure 4-45 amorphous silicon semiconductor
electronic density of states model
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(2) Optical Properties
Figure shows a typical a-Si ray absorption spectroscopy.
Described in the a region, migration between the valence
electrons with the conduction band of the optical Tauc region.
 E nE  E  E 0 m
 ( E ) n / E   E  E 0 m
N is the refractive index
M is a positive number
E0 is the optics can order gap is virtual volume
圖4-46 非晶矽半導體之光吸收係數光譜特徵
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Electronic and positivehole lifetime Fermi level
dependence on silicon
At present , the general solar gradeaSi Tauc Gap around 1.75 ~1.80eV.
About the hydrogen content is
inversely proportional to the change .
If more alloying can be produced as
shown in Figure wide range under the
Tauc Gap, that is the absorption
coefficient spectra and conductivity
different marerials
圖4-47 a-Si上電子及正孔(電洞)壽命費米準位依存性
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(3) Electrical properties
Room temperature, the conductivity in the mobility of
end near the DC conductivity σ (T)
The following formula (4.22)
 T   0 exp  c   F  / kT 
σ0Known as the exponential factor of the
conductivity of the pre-
εcfor the end of mobility (transport energy)
εFfor the Fermi quasi-bit
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The conductivity of a-Si alloy materials under
the irradiation of light
Figure 4-48
shows some new Filmforming method from a-of
SiGe and optical
conductivity of a-SiC
alloys σ ph and dark
conductivity σdark The
Tauc Gap dependence.
圖4-48 The conductivity of a-Si alloy
materials under the irradiation of light
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(4) Doping Feature
Figure 4-49 shows the data from
the spear Against the a-Si done
Doping special Sex. By the
impurity Doping Control of p and
n-layer conductivity controlled
System in 1011S/cm to 102S/cm,
Room. Important for Doping
efficiency Sui Gas Doping 1/2
power Inversely proportional to
the rate of decline, and the lack
of Membrane Trapped in pairs
due.
圖4-49 a-Si Impurity Doping due to the electrical
conduction type and conductivity control cases
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4-3-3 Solar cell structure and
preparation process
1. Solar cells constructed
The basic structure of the pin junction, the general p-layer
thickness of about 50 ~ 200A, ι, layer 4000 ~ 6000A thick nlayer thickness, while around 100 ~ 300A.
Doping had the a-Si materials, even if the optical conductivity
and high defect density due to tectonic Degree, it is the internal
electric field in the width of the area, not Dope (ι, type) field Hop
to narrow. Therefore, pin joints constitute the transport layer
that is photocurrent generated In ι layer, the p and n layers can
be made ​to promote the Carrier, Drift ι layer containing potential.
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The high efficiency of(1) wide Band Gap and
a variety of solar cell
conduction of Dope high
material formed uneven
structure
圖4-50 The high efficiency of a
variety of solar cell structure
bonding window structure.
(2) inside metal layer to the
the Texture substrate and
high reflectivity to light to
capture the effect,
increase the degree of
light absorption layer ι.
(3) combined with the more
narrow than the a-Si
Band Gap materials to
form a laminate structure.
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Integrated layer-type a-Si solar cell
basic structure
a-Si solar cell sub module (module) as shown in Figure 4-51 laminated
To manufacture. Has nothing to do with the external wiring of the thin film
integrated process, as the basic battery connected to any segment
parallel to the formation of deputy modules.
Figure 4-51 integrated layer-type a-Si solar cell
basic structure
TCO: Transparent Conductive Oxide
ITO: In-Sn-O, Indium Tin Oxide
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Method the formation of amorphous silicon
solar cell manufacturing equipment in
accordance with the pin s paration
Shown in Figure 4-52,
p.i.n layer Separation of
the general mining With.
Figure 4-52 (a) below,
The general use of the
batch. However, if then,
as the SUS Sheet Figure
4-52 (b) using the Roller
to Roller ways to increase
students Productive.
Figure 4-52 according to the pin separation method
the formation of amorphous silicon solar cell manufacturing equipment
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Continuous automated process
Use of laser processing technology, as shown in Figure 4-53
(single glass substrate bonding of solar power Pool cases),
automation, a large area and continuous quantity production
process, with the power The increase of power demand, the
future can be realized.
圖4-53 Continuous automated process
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4-3-4 Actuation characteristics of solar cell
1. p-i-n junction solar cells–(1) Actuation of analytical models
Shown in Fig 4-54, the basic structure of the a-Si solar cells p-i-n junction,
In this have a large ( built-in field, Eb). In this region general light irradiation
bulk density large values ​in the (Heat balanced).
Fig.4-54 pin junction and pn junction solar cell energy level
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p
n
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As+
Bh+
(a)
e–
M
M
Metallurgical Junction
Eo
Neutral p-region
E (x)
Neutral n-region
–Wp
0
Wn
x
(e)
(b)
–Eo
V(x)
M
log(n), log(p)
Wp
Wn
Vo
Space charge region
(f)
depletion region
ppo
x
nno
Hole diffusion from
the left to the right
(c)
ni
PE(x)
pno
npo
Hole PE(x)
x
x=0
net
eVo
x
M
eNd
(g)
Electron PE(x)
–Wp
x
Wn
(d)
–eVo
-eNa
Properties of the pn junction.
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Voltage dependence of the photocurrent calculation
Fig. 4-55 Will be normalized bias voltage (V/Vb) dependence of
the photocurrent Jph(V), Ln(=Lp)/d for the variable.
Ln: Electronic diffusion distance
Lp: Hole diffusion distance
FF  C1  C 2
d
Ln  L p
kT
qVb
In C1~0.86，C2~1.9. the resulting fill
factor (FF)、 (Ln、Lp) and built-in
potential (Vb) is correlation, film
thickness (d) is not relevant
Fig. 4-55 Voltage dependence of the photocurrent calculation
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(2) General solar cell characteristics
When ι layer thickness increase, the amount of light is
absorbed, also increase in the photocurrent, its style in Fig 456(a). conversion efficiency η changes in Fig. (b)Vb=0.9V.
conversion efficiency with the diffusion length by the optimized
thickness.
Fig. 4-56 General solar cell characteristics
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Solar cell fill factor of the irradiation light wavelength
dependency calculation
Fig. 4-57 to a variable minority
worried Mode, to calculation solar
cell fill factor of the irradiation light
wavelength dependency (Is a
general, the horizontal axis is the
optical absorption coefficient α)
Fig. 4-57 Solar cell fill factor of the irradiation light wavelength
dependency calculation
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(3) Built-in potential and open-circuit voltage
• Built-in potential (Vb) is important
parameter to dominate the a-Si
solar cells, defined for the builtin field integral value of Eb in ι
layer region, shown in Fig. 4-58
pin unevenly a junction
structure, the Vb available
approximation of the following
formula to represent.
Vb  Eoi   p   n   pv / i   ic/ ni   p d p   n d n 
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A variety of joint purchase into the built-in electric field
and the open circuit voltage relationship
Fig. 4-59 is a variety of different
bonding structure, use Electro
Absorption method to measured Vb
and Voc (AM-1，100mW/cm2)
relationship. With the expansion of p
or n layer Gap, and the conductivity
increases, Vb is increased from 0.8V
to 1.2V. Voc to increase with the
increase of Vb of 0.95V, but more
than is the saturation.
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In addition, the Voc is available the following formula to approximate
Voc  Vb  
d
0
 d ( x)
Eb ( x)dx
 ( x)
σd and σ is the thermal equilibrium and conductivity
irradiation, proportion about the irradiation of the
virtual Fermi level separation degree. near ι layer
central, This ratio (σd /σ) is quite small, therefore, Its
built-in electric field can contribute to the Voc.
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2. Multilayer structure solar cells
Using a Tauc Gap the E0 of
the a-Si alloy produced by
the solar cell, expectations of
short-circuit photocurrent Jsc
(In conditions AM-1.5,
100mW/cm2 absorption of light
quantum value), and built-in
potential, Open-circuit voltage
Vocin Fig 4-60.
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3. Conversion efficiency expectations
conversion efficiency
2.layers of
laminated solar cell
1.single junction
solar cell
1.single junction solar cell
E0=1.75eV of a-Si is 14.2%，E0~1.5eV of
a-Sialloy maximum is 14.7%
Maximum conversion efficiency is 14 ~
15% of research and development target
2.layers of laminated solar cell
The upper part of the a-Si (E0=1.75eV)，
The lower part of the materials used E0 ~
1.4eV a-Si alloy
Conversion efficiency to the measured
value of 15.5%
Fig 4-61 Use of a-Si alloy single-junction and the two layer
laminated structure on solar cells the estimated conversion efficiency
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4-3-5 High-efficiency technology
1. p layer connected technology
In the 3-3 Description of amorphous solar cells pin type for general.
Because as the window layer, it is also effective to remove the load of
the body. Need to be able to form a high quality of the internal electric
field on the p layer, solar cells has reached a high efficiency.
1981 due to the use of widegap (Wide-Gap) material a-SiC,
making the increase of a-Si cell
characteristics. Opens the p
layer of the material and
tectonic studies. P-layer
characteristics and solar cell
characteristics of the relevant
Series in Table 4-6
Solar cell
characteristics
relevant characteristics of the P layer
ISC
Light draw coefficient
Index of refraction
Voc
Fermi preparation(Activation energy)
FF, Voc
TCO/p, ,/iInterface characteristics
P-layer thickness and properties
of homogeneous surname
Table 4-6 Solar cell characteristics and the relationship
of the p-layer characteristics
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4-3-4 Solar cells for moving characteristics
1. PIN junction solar cell–(1) Actuation of analytical models
Fig.4-54 shown in the model , the basic structure of a-Si
solar cells for the pin junction, have a lot of built-in electric
field(built-in field，Eb). In this area, bear body density
general rays dark (thermal equilibrium), value is the larger.
Fig. 4-54 pin junction and pn junction solar cell energy levelconstruct
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(1) p-layer material due to solar cell efficiency
Fig. 4-62 for the use of a - SiC
formed by plasma CVD method, I-V
characteristics of the p layer of solar
cells to increase in cases. This is
because the a-SiC p layer of the
reduced absorption coefficient and
the Gap of Wide.。However, the p
layer of the membrane properties are
not fully there is a low FF problem to
be solved.
Figure 4-62 on the p layer of a-Si
and a-Si solar cell characteristics
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P-type a-SiC film light conductivity and
optical Gap relations
Optical conductivity
Fig. 4-63 relationship between used
up by CVD to form a p-type conductivity of
a-SiC film and Tauc plot income optical
Gap (Eopt). B(CH3)3 conductivity rate
higher than B2H6 10 times or more . Other
cases of the use of BF3 review, the use of
BF3 due to decomposition of the energy
needed for higher. So used the method of
pulse plasma CVD. However, the current
characteristics of not more than B2H6and
B(CH3)3
Optics
Figure 4-63 P-type a-SiC film
optical conductivity and
optical Gap
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ECR plasma CVD & RF plasma CVD
Dark conductivity
Fig. 4-64 for the dark
electrical conductivity and the
optical Tauc plot are asking
Gap relations, μC-SiC above
2eV Wide-Gap, 105 times
more conductive than
traditional a-SiC.
Optics
Figure 4-64 the ECR plasma CVD and RF plasma CVD, the formation
of the P layer of dark conductivity and optical Gap relationship
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2. ι layer connected intrinsic
In the non-crystalline solar cells, generating layer ι layer on the
cell characteristics and most influential large. ι layer is generally of
a-Si: H
(1) The improvement of the reactor
ι layer of oxygen or nitrogen impurities or p layer and n-tier
Doping materials pollution ι membranous lower layer reason.
Reduce the amount of devices of impurities. Aforementioned
separation forming method proposal. Followed by the Hot Wall,
type reactor. In addition, inhibition of the degassing of the
chamber wall, improve the vacuum, the supply of high purity
gases, which can effectively reduce the amount of impurities of aSi: H film.
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(2) Review the reaction conditions
Figure conductivity, optical Gap, etc. has nothing to do with
the other reflects the conditions. Determined by the balance of
film speed and substrate temperature. That is not a party to the
conditions constraints, but will enable the optimization of a-Si:
H-the membrane properties.
Fig. 4-65 a variety of reaction pressure, RF power and gas flow
under the form of a-Si: H film
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H2 diluted with no H2 diluted a-of
SiGe film conductivity on the optical map
Figure 4-66 for the a-of SiGe optical
conductivity The example of the
rate increase due to hydrogen
dilution. Optical conductivity of the
hydrogen dilution particularly in
the optical Gap narrow, membrane
containing large amounts of Ge
occasions than dilution increase
greater.
P--------i----------n
SiC SeGe
Figure 4-66 H2 diluted with no H2 diluted a-of
SiGe film optical diagram conductivity
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(3) n-layer related technology
N-tier generally of a-Si solar cells
, P (phosphorus) Dope of the a-Si:
H. The actual features on the solar
cell, N-tier than the p-layer
or the ι layer of hard anti
reflect the membrane properties.
Because in the pin group
synthetic battery,n-tier living into
the light the lower of the exit
surface, light absorption less
the reasons.
Figure 4-67 n-type of μc-Si optical map and
Doping amount of dependency of conductivity
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p/i interface Buffer layer concept
and characteristics of the battery
p / ι, the interface absorption in the
neighborhood of the harvests light,
bear body likely to affect features.
The p-layer a-SiC:H as much,
andιlayer of a-Si:H, this structural
difference Quasi-circles of bites, so
use the buffer layer. Figure 4-68
buffer layer of conductivity entry can
be seen in the open voltage and
short circuit photocurrent the
increase of the current.
異質接
面
Figure 4-68
p/i interface Buffer layer concept
and characteristics of the battery
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3. Optical storage technology
Since ancient times in the single-crystalline silicon solar cells to anisotropic etching tobuild
into μm to tens of μm unit pyramid uneven CNR (comsat start a non-reflective solar cell).
The effect of:
(1) the multiple reflections of the surface to reduce surface reflection.
(2) of light refraction effect born of the optical path length of the longwavelength lightabsorption.
a-Si solar cell initially this
technology is Exxon
Deckman,etc., is shown in Figure
4-69Metal on a glass substrate
bump, can take
the light scattered chaos.
Figure 4-69 the initial use of a-Si solar
cell cases .
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4-3-6 Stability and reliability
1.
2.
An amorphous plasma membrane of the photodegradation
light of the a-Si film deterioration phenomenon is known as the StaeblerWronski effect.
Figure 4-70 for the ESR
method to change the light
intensity, measured Dangling the
bond defects generated with the
following formula, calculate the results.
N S t   CSW G
2 / 3 1/ 3
t
Ns is the Dangling Bond, defect density
Csw combination of rebirth for
the Band connection between
the rate constants of dangling Bond defects
Figure 4-70 defect density changes in light exposure time
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Light irradiation time of the change of defect density
Said that the characteristics of
a-Si Stretched the exponential
dispersion process isoften used,
performance Dangling the bond
defect generation process is
also oftenreview.As shown,the
computability with saturation of
the defect density of light
irradiationborn.
Figure 4-71 defect density changes in light exposure time
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Photodegradation defect density after heat
treatment changes
Figure 4-72 for the
photodegradation of a-Si dangling the
bond amount reduced due toheat
treatment and style, the ESR
measurement, the heat treatment
process, high temperature faster.
Figure 4-72 photodegradation
defect density after heat treatment changes
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2. the light degradation of solar cells
Light irradiation in a-Si membrane
of Dangling the bond born defects,
will encumber the electronic
and positive holes generated in the solar
cells within the flow, so that light from
the electrical characteristics of the low.
Figure
4-73 for typical light degradation characteristics.
Long light exposure, lower in FF, resulting in
low efficiency.
Figure 4-73 a-Si solar cells,
long-term optical degradation characteristics
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a-SiSolar cells due to photodegradation born energy
level
style
changes
Figure 4-74
shows the energy level diagram of a-Si
solar cell (a) initial (b) after lightirradiation.Early: that battery electric
field generated diffusion potential due to the pinbetween the in ι layer of the
whole region, the light generated electrons and positronsholes are
attracted to the n layer and p layer, the result of
a power.Light irradiation:Dangling the bond defects generated
in the formation of space charge in the p layer and n near to ι layer of the
central field was reduced and the system electronics and holeeasily
separated, combined with defects Erzhi mostly been eliminated.
Figure 4-74 a-Si solar cells due to light degradation born energy level style changes
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