Chapter 4 - variety of solar cells

National Formosa University

Institute of Electro-Optical and Material Science

Chapter 4 - variety of solar cells

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Chapter 4 - variety of solar cells4-1 單晶矽太陽電池 (single crystal Si)

Bulk, wafer type4-2 多晶矽太陽電池 (poly crystal Si)

Wafer type4-3 非晶矽太陽電池 (amorphous Si)

Thin film type4-4 化合物半導體太陽電池

Compound semiconductor4-5 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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4-1-14-1-1 SummarySolar 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 Semiconductor materials市場模組發電轉換效率

晶矽Crystalline

單晶矽Single Crystalline

12~20%

多晶矽Poly Crystalline

10~18%

非晶矽Amorphous

Si、 SiC、 SiGe、 SiH、 SiO

6~9%5



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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4-1-24-1-2 構造構造 – – (1) (1) 基本構造基本構造• 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光起電力效果之少數載體效應depletion region in PN junctiondepletion region in PN junction

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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接合n p

Lp Ln

光

Xj



(2) (2) 淺接合構造淺接合構造

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)(3) BSF(Back Surface Field) 構造構造如圖 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10



含有含有 BSFBSF 構造之太陽電池能階模式構造之太陽電池能階模式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

圖 4-4 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 P+

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2.2. 電極構造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 )12



BSRBSR 構造構造

圖 4-6 BSR 構造 ( 附 BSF 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。

裏面電極裏面反射膜(Al或Au)

反射防止膜表面電極

n+

p

p+ BSFBSF

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3.3. 封存光之構造封存光之構造 (Light (Light trapping)trapping) (1)By anti-reflection film(1)By anti-reflection film(2)By texture surface or roughness(2)By texture surface or roughness

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。

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

λ=4nd， n2=nsi no

(1)(1) 反射防止膜反射防止膜 -1 -1 (anti-reflection film)(anti-reflection film)

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(1)(1) 反射防止膜反射防止膜 -2-2

圖 4-7 以實線表示 Si 之反射特性與施以折射率為 2.25 時之反射防止膜

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

P-type Si

N-type SiITO

Al

Al

P-type Si

N-type SiITO

(1)

(2)

(3)

(4)

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(2)(2) 組織組織 (Texture)(Texture) 構造構造 -- 粗糙化粗糙化 (texture, (texture, roughness)roughness)

by etching on the Si surfaceby 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 16



4-1-34-1-3 單晶矽太陽電池之製作法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。

圖 4-9 單晶矽太陽電池之製作流程

硅石SiO2

金屬級Si 矽烷氣體多晶矽單晶矽切割

Texture處裡

研磨.蝕刻接合成形電極成形反射防止膜電池

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(1) (1) 氣體擴散法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 18



(2) (2) 固相擴散法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

此不純物分佈在圖 4-10 中以點線表示。

DtDt

NxN xo

4exp)(

2

DtDt

NxN xo

4exp)(

2

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(3)(3) 離子注入法離子注入法不純物分 N(χ) 依高斯分佈

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 )

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。

2

2

2exp

2)(

RxN

xNo

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BSRBSR 構造構造：：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21



4.4. 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。

表 4-1 各種材料的折射率

材料折射率SiO2

MgF2

SiO2-TiO2

Al2O3

CeO2

1.44

1.44

1.80~1.96

1.86

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

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(2)(2) 組織構造組織構造前述之 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23



4-1-44-1-4 單晶矽太陽電池之高效率化單晶矽太陽電池之高效率化 1.1. 理論效率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

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 ) 。

Pin

IscVocFF

Pin

Vm

Pin

Pm

Im

FF=(ImVm) / (IscVoc)FF=(ImVm) / (IscVoc)

Fill FactorFill Factor24



太陽電池的光照射特性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25



2.2. 高效率化基本考量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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氧化物誘起之氧化物誘起之 HLHL 接合接合圖 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

(AM-0， 25度 )圖 4-16 氧化物誘起之 HL 接合

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NINPNINP 構造太陽電池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29



4-1-54-1-5 高效率單結晶矽太陽電池高效率單結晶矽太陽電池1.1. 平面型太陽電池平面型太陽電池 - - (1) PESC(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，增大光電流。

圖 4-18 PESC 之構造

P

反射防止膜

極薄酸化膜

表面電極

裏面電極

n

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(1) PESC(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(2) μg PESC

圖 4-19 μg PESC 構造

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。

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(3) PERC(passivated emitter rear cell)(3) PERC(passivated emitter rear cell) 電池電池太陽電池裡面 passivation 之重要性的 PERC 構造畫在圖 4-

20 。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)(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)(5) 電極埋入式太陽電池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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2.2. 大面積太陽電池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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3.3. 集光型太陽電池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。

37



(1)(1) 點接觸型點接觸型• 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

圖 4-23 點接觸型太陽電池構造

AM-1.5， 100mW/cm2 ，24 度時， Jsc=41.5mA/

cm2

， Voc=582mV， FF=0.786

， η=22.2%

38



(2) (2) 微細溝型微細溝型 (micro groove)(micro groove)

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。

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%

39



Prismatic CoverPrismatic Cover 之原理之原理圖 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。圖 4-25

Prismatic Cover 之原理

40



4-1-64-1-6 今後的課題今後的課題• 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。

41



4-24-2 多晶矽太陽電池多晶矽太陽電池

42



4-24-2 多晶矽太陽電池多晶矽太陽電池 4-2-1 多晶矽材料之形成 4-2-2 結晶粒界之電氣特性及不活性化 4-2-3 接合構造及理論效率 4-2-4 太陽電池製造技術 4-2-5 將來展望

43



4-24-2 多晶矽太陽電池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。

44



4-2-1 4-2-1 多晶矽材料之形成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。

45



矽中金屬不純物及其大略容許量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 。

表 4-2 矽中金屬不純物及其大略容許量

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

46



轉換效率的結晶粒徑依存性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50μm 以上之結晶粒徑要求。

圖 4-26 轉換效率的結晶粒徑依存性 ( 實線虛線各為無光封存，載體封存效果之

理論值 )

47



液相矽基板製造法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

48



SilsoSilso 製造裝置概略圖製造裝置概略圖

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49



電磁鑄造法之理論圖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50



S-WedS-Wed 法原理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51



SCIM(silicon coating by inverted meniscus)SCIM(silicon coating by inverted meniscus)法法陶瓷表面、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

52



RAFT(ramp assissted foil casting)RAFT(ramp assissted foil casting) 法原理法原理

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

53



Cast RibbonCast Ribbon 法制備矽薄板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54



4-2-24-2-2 結晶粒界之電氣特性及不活性結晶粒界之電氣特性及不活性化化 1. 1. 結晶粒界的物性及光電特性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

55



2. 2. 粒界的特性評估法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。

表 4-3 結晶粒界的特性評估法

手法具體分析技術

結晶學的評估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)56



單色光勵起電流像法單色光勵起電流像法 (Monochromatic-light(Monochromatic-lightbeam induced currentbeam induced current，， MBIC)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

57



4-2-34-2-3 接合構造及理論效率接合構造及理論效率 1. 1. 多晶太陽電池作動之理論解析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。

58



結晶粒界考量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

長為 A 之正方形結晶粒

再結合速度 S

減衰常數為代表結晶粒夠大

gfil A

D

1

2

12

2

gfil A

S

11

g

gfil

59



結晶粒界的電荷狀態與太陽電池特性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。

表 4-4 結晶粒界的電荷狀態與太陽電池特性

構成

Base Emitter 可預期特性粒內

粒界

粒內

粒界

1

2

3p p+ n

n+ 低 Voc

n- 最佳p 低 Voc

4

5

6p p- n

n+ 佳n- 佳p 低 Voc

7

8

9p n n

n+ 低 Jsc

n- 低 Jsc

p 低 Jsc

60



高效率之結晶粒界的電荷狀態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

61



2. 2. 光封存及擔體光封存及擔體 (( 載子載子 ,carrier),carrier) 封存封存

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。

圖 4-37 光封存構造

光

(a)傾斜裏面構造

α

接合

(b)裏面Texture構造

Si

透明基板

Si

62



3.3. 各種高效率太陽電池構造各種高效率太陽電池構造(1) 多晶厚膜電池

表 4-5 多結晶矽太陽電池的出力特性

元件構造開放端電壓(mV)

短路光電流(mA/cm2)

曲線率(%)

轉換效率(%)

受光面積(cm2)

厚膜機械 V溝構造3 電極BSNSC

Cast Ribbon

601611611596

36.535.435.437.4

77.875.975.975.4

17.116.416.416.8

100100125100

薄膜陶瓷基板金屬級 Si基板

593608

32.430.0

74.0781

14.214.2

0.98100

63



機械的機械的 VV 溝構造電池模式圖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64



33 電極電極 BifacialBifacial 電池之構造電池之構造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

65



BSNSCBSNSC 之構造之構造而 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66



圖 4-41 典型的厚膜多晶矽太陽電池製程67



4-34-3 非晶矽太陽電池非晶矽太陽電池amorphous Siamorphous Si

微晶矽微晶矽micro crystal Simicro crystal Si

μc-Siμc-Si

68



4-3 非晶系太陽電池 amorphous Siamorphous Si

4-3-1 conspectus

4-3-2 Preparation and properties of amorphoussilicon

4-3-3 Solar cell structure and preparation process

4-3-4 Solar cells for moving characteristics

4-3-5 High-efficiency technology

4-3-6 Stability and reliability

69



4-3-1 4-3-1 conspectusPECVD: plasma enhanced chemical vapor deposition

Amorphous solar cells dates back to the early 1970s, tothe plasma CVD method , SiH4 gas preparation of amorphous silicon film, visible light, has a large absorption coefficient, andexcellent 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.70



Amorphous silicon solar cell conversion efficiency changes

71

TandemTandem

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.



4-3-2 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.

72



(1) Plasma Enhanced Chemical Vapor Deposition (1) Plasma Enhanced Chemical Vapor Deposition (PECVD)(PECVD) 法法

圖 4-43 電漿 CVD法材料氣體至成膜之個種形成

73

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.



Capacity bound Plasma Enhanced CVD Plasma Enhanced CVD (PECVD) (PECVD) device concept

圖 4-44 容量結合型 Plasma CVD裝置概念

13.56 MHz13.56 MHz

60 MHz60 MHz

74

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.



(1) (1) Structure and electronic stateHave 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.

75

Figure 4-45 amorphous silicon semiconductor electronic density of states model



(2)(2) Optical PropertiesFigure 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.

圖 4-46 非晶矽半導體之光吸收係數光譜特徵

N is the refractive index

M is a positive number

E0 is the optics can order gap is virtual volume

m

m

EEEnE

EEnE

0

0

/)(

E

76



Electronic and positivehole lifetime Fermi level dependence on silicon

At present , the general solar gradea-Si Tauc Gap around 1.75 ~1.80eV. About the hydrogen content is inversely proportional to the change .

圖 4-47 a-Si 上電子及正孔 ( 電洞 )壽命費米準位依存性77

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



(3) (3) Electrical propertiesElectrical properties

σ0Known as the exponential factor of the conductivity of the pre-

εcfor the end of mobility (transport energy)

εFfor the Fermi quasi-bit

Room temperature, the conductivity in the mobility of end near the DC conductivity σ (T)

The following formula (4.22)

kTFc /expT 0

78



The conductivity of a-Si alloy materials under The conductivity of a-Si alloy materials under the irradiation of lightthe irradiation of light

Figure 4-48

shows some new Film-forming 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

79



(4) Doping Feature(4) Doping Feature

圖 4-49 a-Si Impurity Doping due to the electrical conduction type and conductivity control cases

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.

80



4-3-3 Solar cell structure and 4-3-3 Solar cell structure and preparation processpreparation process1. Solar cells constructed The basic structure of the pin junction, the general p-layer

thickness of about 50 ~ 200A, ι, layer 4000 ~ 6000A thick n-layer 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.

81



The high efficiency of The high efficiency of a variety of solar cella variety of solar cell structure structure

(1) wide Band Gap and conduction of Dope high material formed uneven 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.

圖 4-50 The high efficiency of a variety of solar cell structure

82



Integrated layer-type a-Si solar cell Integrated layer-type a-Si solar cell basic structurebasic 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 OxideITO: In-Sn-O, Indium Tin Oxide

83



Method the formation of amorphous silicon Method the formation of amorphous silicon solar cell manufacturing equipment in solar cell manufacturing equipment in accordance with the pin s parationaccordance 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 equipment84



Continuous automated processContinuous automated processUse 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 process85



4-3-44-3-4 Actuation characteristics of solar Actuation characteristics of solar cellcell

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 level86



nno

xx = 0

pno

ppo

npo

log(n), log(p)

-eNa

eNd

M

x

E (x)

B-

h+

p n

M

As+

e–

Wp Wn

Neutral n-regionNeutral p-region

Space charge region Vo

V(x)

x

PE(x)

Electron PE(x)

Metallurgical Junction

(a)

(b)

(c)

(e)

(f)

x

–Wp

Wn

(d)

0

eVo

x (g)

–eVo

Hole PE(x)

–Eo

Eo

M

net

M

Wn–Wp

ni

Properties of the pn junction.

© 1999 S.O. Kasap, Optoelectronics (Prentice Hall)

Hole diffusion from the left to the right

depletion region

87



Voltage dependence of the photocurrent calculation 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

Fig. 4-55 Voltage dependence of the photocurrent calculation

bpn qV

kT

LL

dC

21CFF

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

88



(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 4-56(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 characteristics89



Solar cell fill factor of the irradiation light wavelength dependency calculation

Fig. 4-57 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)

90



(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 built-in 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.

nnppc

niiv

ipnpoib ddEV //

91



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.

92



In addition, the Voc is available the following formula to approximate

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.

dxxEx

xVVoc b

dd

b )()(

)(0

93



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.

94



3. Conversion efficiency expectations3. Conversion efficiency expectations

95

1.single junction solar cell1.single junction solar cellE0=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 target2.layers of laminated solar cell2.layers of laminated solar cellThe upper part of the a-Si (E0=1.75eV) ，The lower part of the materials used E0 ~ 1.4eV a-Si alloyConversion efficiency to the measured value of 15.5%

2.layers of 2.layers of laminated solar celllaminated solar cell

1.single junction 1.single junction solar cellsolar cell

conv

ersi

on

effi

cien

cy

Fig 4-61 Use of a-Si alloy single-junction and the two layer laminated structure on solar cells the estimated conversion efficiency



4-3-54-3-5 High-efficiency technologyHigh-efficiency technology 1. p layer connected technology1. 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 wide-gap (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

Table 4-6 Solar cell characteristics and the relationship of the p-layer characteristics

96

Solar cell Solar cell characteristicscharacteristics

relevant characteristics of the P layerrelevant characteristics of the P layer

ISC Light draw coefficientIndex of refraction

Voc Fermi preparation(Activation energy)

FF, Voc TCO/p, ,/iInterface characteristicsP-layer thickness and properties of homogeneous surname



4-3-44-3-4 Solar cells for moving characteristicsSolar cells for moving characteristics1. 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 levelconstruct97



(1) p-layer material due to solar cell efficiency(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 characteristics98



P-type a-SiC film light conductivity and P-type a-SiC film light conductivity and optical Gap relationsoptical Gap relations

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

Figure 4-63 P-type a-SiC film optical conductivity and optical Gap

99

Opt

ical

con

duct

ivit y

OpticsOptics



ECR plasma CVD ECR plasma CVD & & RF plasma CVDRF plasma CVD

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.

Figure 4-64 the ECR plasma CVD and RF plasma CVD, the formation of the P layer of dark conductivity and optical Gap relationship

100

Dar

k D

ark

cond

uctiv

ityco

nduc

tivity

OpticsOptics



2. 2. ι ι layer connected intrinsiclayer 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 a-Si: H film.

101



(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

102



H2 diluted with no H2 diluted a-of H2 diluted with no H2 diluted a-of SiGe film conductivity on the optical mapSiGe 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, membranecontaining large amounts of Ge occasions than dilution increase greater.

P--------i----------nSiC SeGe

Figure 4-66 H2 diluted with no H2 diluted a-of SiGe film optical diagram conductivity

103



(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 solarcell, N-tier than the p-layeror the ι layer of hard antireflect the membrane properties.Because in the pin groupsynthetic battery,n-tier living intothe light the lower of the exitsurface, light absorption lessthe reasons.

Figure 4-67 n-type of μc-Si optical map and Doping amount of dependency of conductivity

104



p/i interface Buffer layer concept p/i interface Buffer layer concept and characteristics of the batteryand characteristics of the battery

Figure 4-68

p/i interface Buffer layer concept

and characteristics of the battery

異質接異質接面面

105

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.



3. 3. Optical storage technologyOptical storage technology

a-Si solar cell initially this technology is ExxonDeckman,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 .

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 long-wavelength lightabsorption.

106



4-3-64-3-6 Stability and reliabilityStability and reliability 1. An amorphous plasma membrane of the photodegradation

2. light of the a-Si film deterioration phenomenon is known as the Staebler-Wronski 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.

Figure 4-70 defect density changes in light exposure time

3/13/2 tGCtN SWS Ns is the Dangling Bond, defect density

Csw combination of rebirth for

the Band connection between

the rate constants of dangling Bond defects

107



Light irradiation time of the change of defect densityLight 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 lightirradiationborn.

Figure 4-71 defect density changes in light exposure time

108



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

109



2. the light degradation of solar cells

Figure 4-73 a-Si solar cells,

long-term optical degradation characteristics

110

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.



a-Sia-SiSolar cells due to photodegradation born energy Solar cells due to photodegradation born energy level style changeslevel style changes

111Figure 4-74 a-Si solar cells due to light degradation 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.

Documents

Chapter 4 - variety of solar cells