太陽能電池的原理及製作
Solar cells elements, how solar cells work. .(英文)
Solar energy is inexhaustible renewable energy for humans. It's also clean energy, do not generate any environmental pollution. Solar photovoltaic was the most watched item in the researching of solar energy utilize.
The production of solar cells based on semiconductor materials, and its working principle is photovoltaic materials photoelectron conversion reaction after absorb light energy , according to different materials, solar cells can be divided into: 1, silicon solar cells; 2 multi-material cells using inorganic salts such as gallium arsenide III-V compounds, cadmium sulfide, copper indium selenium compounds; 3, polymer materials solar cells; 4, nano-crystalline solar cells. etc.
1.Silicon solar cells
Silicon solar cell's structure and working principle,
Solar cells' elements is the photoelectric effect of semiconductors, normally simiconductors have below structure:
As shown in the picture, positive charge(+) means silicon atom, negtive charge(-) means electron around the silicon atom.
A hole will exist in the crystalline silicon when the cyrstalline silicon mixed with boron, it's shape as below picture:
In the picture, Positive charge (+) means silicon atom, Negetive charge(-) means electron around the silicon atom. and the yellow means mixed boron atom, as only 3 electron around the boron atom, it's bring the hole as in blue, this hole is unstable as it's without electron, easily absorb electron to neutralize to be a P(positive) type semiconductor.
Sameness, when mixed with phosphor atom, it's become highly active as the phosphor atom have 5 electron, it's comes the N(negative) type semiconductor. as shown in below picture, the yellow means Phosphor atom, the red means superfluous electron.
N type semiconductor contains more hole, while the P type semiconductor contains more electron, in this way, the electric potential difference will be formed when the P and N type semiconductor combine, that comes the PN junction.
When the P and N-type semiconductor combine, the two types of semiconductors at the interface region will form a special thin-layer, the P side contains negative electron, N side contains positive electron. This is because P-type semiconductor have many hole, N-type semiconductor have many free electrons. Electron from N-zone will be spread to the P-zone, hole from the P-zone will spread to the N-zone.
When the lights reach the crystalline silicon, the hole from N-type semiconductor move to P zone, and electron from P-zone move to N-zone, that formed the electric current from N-zone to P-zone, then formed the electric potential difference, that comes the electricity source. (shown in below picture)
Because the semiconductor is not a good conductor of electricity, the electron will waste very much when passed the P-N junction and flow in semiconductor as it's large resistance. However, if painted a metal upper, sunlight can not going through, electric current will not be able to produce, so in general with a metal mesh covering the p-n junction (pectinate electrode), in order to increase the size of the incident light.
In addition, the silicon surface is very bright, will reflect many of the sun lights,could not be used by the solar cells. Therefore, scientists painted it with a very small reflectance film, to decrease the sunlights reflection loss below 5% or eve less. A single solar cell can provide only a limited current and voltage, so people join many pieces of solar cells (usually 36) in parallel or series to become the solar modules.
2.Crystalline silicon solar cell manufacturing process.
Usual crystalline silicon solar cells are made up from the high-quality silicon at thickness of 350 ~ 450μm, such silicon wafers are cutted from Czochralski or casted silicon ingot
The above method consum more silicon material. In order to save materials, the current preparation of polycrystalline silicon thin-film solar cells using chemical vapor deposition method, including low pressure chemical vapor deposition (LPCVD) and plasma enhanced chemical vapor deposition (PECVD) process. In addition, liquid phase epitaxy (LPPE) and sputtering deposition method can also be used to prepare poly-silicon thin-film battery.
Chemical vapor deposition mainly the SiH2Cl2, SiHCl3, SiCl4 or SiH4, as the reaction gas,It's react at a certain protection atmosphere and deposite silicon atoms at the heated substrate, the general substrate materials are Si, SiO2, Si3N4, etc.. But the researching found that it's difficult to form the large crystal on the amorphous silicon (a-si) substrates and easy to cause interspace between crystal. Solutions for this problem is to deposite a thin layer of amorphous silicon on the substrate by LPCVD, then annealing this layer of amorphous silicon, to get larger crystal, and then deposite a more thick poly-crystalline silicon film at this layer, therefore, re-crystallization technology is no doubt a very important aspect, the current technology used is solid-phase crystallization and recrystallization in the FZ method. Polysilicon thin-film solar cells not onlyi use the re-crystallization process, also used almost all of the mono-crystalline silicon solar cells preparation technology, the solar cells made by this way have a remarkablly increased it's conversion efficiency.
3.Nanocrystalline chemistry solar cell
Silicon solar cells are undoubtedly the most sophisticated amone all solar cells, but because of it's high cost, can not meet the requirements of large-scale application. Therefore, Peoples always explore in process, new material and thin film solar cells etc, among this, the newly developed nano TiO2 crystalline chemistry solar cells get a great importance from home and abroad scientists.
For example, the dye-sensitized nanocrystalline solar cells (DSSCs), such solar cells mainly includes a glass substrate deposited with trasparent conductive film, dye-sensitized semiconductor materials, electrode and electrolyte etc.
As shown in below picture, the white ball means TiO2, red ball means dye molecules. Dye molecules transite to excited state after absorb solar energy, excited state unstable, the electron rapidly injected into the nearby TiO2 conduction band, Dye lost the electron is quickly be compensated from the electrolyte, electron enter the conduction band of TiO2 and eventually enter the electric conductive film, and then through the outer loop photocurrent generated.
Nanocrystalline TiO2 solar cells have it's advantages of cheap cost, simple production process and a stable performance. Photoelectric efficiency stability at 10%, and the production costs is only 1 / 5 ~ 1 / 10 of silicon solar cells. Life expectancy can achieve more than 20 years. However, because of such a solar cell researching and development still in its infancy, it is estimated to be in the market gradually.
Anode: dye-sensitized semi-conductive thin film ( TiO2 film)
Cathode: TCO glass deposted with platinic
Electrolyte: I3-/I-
Nanocrystalline chemistry solar cell application model
4 Hand made dye-sensitized nanocrystalline solar cells
1. TiO2 film Preparation
1)Grinding titanium dioxide powder with adhesive mortars
2)Spread the mixture on TCO (transparent conductive) glass
3)Sinter it on alcohol burner,them cool it down.
2.Color up the TiO2 with natural dyestuff
as shown in the picture, extrude the fresh or freezing black berry, Punica granatum seeds or black tea added with a spoon of water, then put the TiO2 film into it for color up, it's need around 5 minutes till the film become modena, if the color is nonuniform for both side, could dip in for another 5 minutes. afterwards, wash it with ethanol, then dry it with soft paper lightly.
3.Make positive electrode,
The electron outflow from dyed TiO2, means negative electrode. The positive electrode could be the conductive side of the TCO glass(the side depsited with SnO2), it's could be distinguish which side of the glass are conductive by a multi meter, also could distinguish by finger as the conductive side more coarseness. as below picture, mark the non-conductive side with "+", and use a pencil wipe the conductive side with a layer of black lead equably,
4.Join the electrolyte
Use the solution with iodin-hydronium to be the electrolyte for solar cells, mainly for revert and rebirth dyestuff. drop 1 or 2 dripping electrolyte on the TiO2 .
5.Assemble the solar cells
Put the color up TiO2 film on the tale facing up, drop on 1 or 2 dripping of iodin-hydronium electrolyte, then put the positive electrode facing down on the TiO2 film. put the 2 glass slightly staggered, use 2 clamps to nip the solar cell, the 2 glass exposed parts are for connect wires. In this way, you maked the solar cells.
6.Solar cell testing:
put the solar cell under sunshine outdoor, test your solar cell if it could generate electric current.
The production of solar cells based on semiconductor materials, and its working principle is photovoltaic materials photoelectron conversion reaction after absorb light energy , according to different materials, solar cells can be divided into: 1, silicon solar cells; 2 multi-material cells using inorganic salts such as gallium arsenide III-V compounds, cadmium sulfide, copper indium selenium compounds; 3, polymer materials solar cells; 4, nano-crystalline solar cells. etc.
1.Silicon solar cells
Silicon solar cell's structure and working principle,
Solar cells' elements is the photoelectric effect of semiconductors, normally simiconductors have below structure:
As shown in the picture, positive charge(+) means silicon atom, negtive charge(-) means electron around the silicon atom.
A hole will exist in the crystalline silicon when the cyrstalline silicon mixed with boron, it's shape as below picture:
In the picture, Positive charge (+) means silicon atom, Negetive charge(-) means electron around the silicon atom. and the yellow means mixed boron atom, as only 3 electron around the boron atom, it's bring the hole as in blue, this hole is unstable as it's without electron, easily absorb electron to neutralize to be a P(positive) type semiconductor.
Sameness, when mixed with phosphor atom, it's become highly active as the phosphor atom have 5 electron, it's comes the N(negative) type semiconductor. as shown in below picture, the yellow means Phosphor atom, the red means superfluous electron.
N type semiconductor contains more hole, while the P type semiconductor contains more electron, in this way, the electric potential difference will be formed when the P and N type semiconductor combine, that comes the PN junction.
When the P and N-type semiconductor combine, the two types of semiconductors at the interface region will form a special thin-layer, the P side contains negative electron, N side contains positive electron. This is because P-type semiconductor have many hole, N-type semiconductor have many free electrons. Electron from N-zone will be spread to the P-zone, hole from the P-zone will spread to the N-zone.
When the lights reach the crystalline silicon, the hole from N-type semiconductor move to P zone, and electron from P-zone move to N-zone, that formed the electric current from N-zone to P-zone, then formed the electric potential difference, that comes the electricity source. (shown in below picture)
Because the semiconductor is not a good conductor of electricity, the electron will waste very much when passed the P-N junction and flow in semiconductor as it's large resistance. However, if painted a metal upper, sunlight can not going through, electric current will not be able to produce, so in general with a metal mesh covering the p-n junction (pectinate electrode), in order to increase the size of the incident light.
In addition, the silicon surface is very bright, will reflect many of the sun lights,could not be used by the solar cells. Therefore, scientists painted it with a very small reflectance film, to decrease the sunlights reflection loss below 5% or eve less. A single solar cell can provide only a limited current and voltage, so people join many pieces of solar cells (usually 36) in parallel or series to become the solar modules.
2.Crystalline silicon solar cell manufacturing process.
Usual crystalline silicon solar cells are made up from the high-quality silicon at thickness of 350 ~ 450μm, such silicon wafers are cutted from Czochralski or casted silicon ingot
The above method consum more silicon material. In order to save materials, the current preparation of polycrystalline silicon thin-film solar cells using chemical vapor deposition method, including low pressure chemical vapor deposition (LPCVD) and plasma enhanced chemical vapor deposition (PECVD) process. In addition, liquid phase epitaxy (LPPE) and sputtering deposition method can also be used to prepare poly-silicon thin-film battery.
Chemical vapor deposition mainly the SiH2Cl2, SiHCl3, SiCl4 or SiH4, as the reaction gas,It's react at a certain protection atmosphere and deposite silicon atoms at the heated substrate, the general substrate materials are Si, SiO2, Si3N4, etc.. But the researching found that it's difficult to form the large crystal on the amorphous silicon (a-si) substrates and easy to cause interspace between crystal. Solutions for this problem is to deposite a thin layer of amorphous silicon on the substrate by LPCVD, then annealing this layer of amorphous silicon, to get larger crystal, and then deposite a more thick poly-crystalline silicon film at this layer, therefore, re-crystallization technology is no doubt a very important aspect, the current technology used is solid-phase crystallization and recrystallization in the FZ method. Polysilicon thin-film solar cells not onlyi use the re-crystallization process, also used almost all of the mono-crystalline silicon solar cells preparation technology, the solar cells made by this way have a remarkablly increased it's conversion efficiency.
3.Nanocrystalline chemistry solar cell
Silicon solar cells are undoubtedly the most sophisticated amone all solar cells, but because of it's high cost, can not meet the requirements of large-scale application. Therefore, Peoples always explore in process, new material and thin film solar cells etc, among this, the newly developed nano TiO2 crystalline chemistry solar cells get a great importance from home and abroad scientists.
For example, the dye-sensitized nanocrystalline solar cells (DSSCs), such solar cells mainly includes a glass substrate deposited with trasparent conductive film, dye-sensitized semiconductor materials, electrode and electrolyte etc.
As shown in below picture, the white ball means TiO2, red ball means dye molecules. Dye molecules transite to excited state after absorb solar energy, excited state unstable, the electron rapidly injected into the nearby TiO2 conduction band, Dye lost the electron is quickly be compensated from the electrolyte, electron enter the conduction band of TiO2 and eventually enter the electric conductive film, and then through the outer loop photocurrent generated.
Nanocrystalline TiO2 solar cells have it's advantages of cheap cost, simple production process and a stable performance. Photoelectric efficiency stability at 10%, and the production costs is only 1 / 5 ~ 1 / 10 of silicon solar cells. Life expectancy can achieve more than 20 years. However, because of such a solar cell researching and development still in its infancy, it is estimated to be in the market gradually.
Anode: dye-sensitized semi-conductive thin film ( TiO2 film)
Cathode: TCO glass deposted with platinic
Electrolyte: I3-/I-
Nanocrystalline chemistry solar cell application model
4 Hand made dye-sensitized nanocrystalline solar cells
1. TiO2 film Preparation
1)Grinding titanium dioxide powder with adhesive mortars
2)Spread the mixture on TCO (transparent conductive) glass
3)Sinter it on alcohol burner,them cool it down.
2.Color up the TiO2 with natural dyestuff
as shown in the picture, extrude the fresh or freezing black berry, Punica granatum seeds or black tea added with a spoon of water, then put the TiO2 film into it for color up, it's need around 5 minutes till the film become modena, if the color is nonuniform for both side, could dip in for another 5 minutes. afterwards, wash it with ethanol, then dry it with soft paper lightly.
3.Make positive electrode,
The electron outflow from dyed TiO2, means negative electrode. The positive electrode could be the conductive side of the TCO glass(the side depsited with SnO2), it's could be distinguish which side of the glass are conductive by a multi meter, also could distinguish by finger as the conductive side more coarseness. as below picture, mark the non-conductive side with "+", and use a pencil wipe the conductive side with a layer of black lead equably,
4.Join the electrolyte
Use the solution with iodin-hydronium to be the electrolyte for solar cells, mainly for revert and rebirth dyestuff. drop 1 or 2 dripping electrolyte on the TiO2 .
5.Assemble the solar cells
Put the color up TiO2 film on the tale facing up, drop on 1 or 2 dripping of iodin-hydronium electrolyte, then put the positive electrode facing down on the TiO2 film. put the 2 glass slightly staggered, use 2 clamps to nip the solar cell, the 2 glass exposed parts are for connect wires. In this way, you maked the solar cells.
6.Solar cell testing:
put the solar cell under sunshine outdoor, test your solar cell if it could generate electric current.
太陽能電池的原理及製作
太陽能是人類取之不盡用之不竭的可再生能源。也是清潔能源，不產生任何的環境污染。在太陽能的有效利用當中；大陽能光電利用是近些年來發展最快，最具活力的研究領域，是其中最受矚目的專案之一。
製作太陽能電池主要是以半導體材料為基礎，其工作原理是利用光電材料吸收光能後發生光電於轉換反應，根據所用材料的不同，太陽能電池可分為：1、矽太陽能電池；2、以無機鹽如砷化鎵III-V化合物、硫化鎘、銅銦硒等多元化合物為材料的電池；3、功能高分子材料製備的大陽能電池；4、納米晶太陽能電池等。
一、矽太陽能電池
1．矽太陽能電池工作原理與結構
太陽能電池發電的原理主要是半導體的光電效應，一般的半導體主要結構如下：
圖中，正電荷表示矽原子，負電荷表示圍繞在矽原子旁邊的四個電子。
當矽晶體中摻入其他的雜質，如硼、磷等，當摻入硼時，矽晶體中就會存在著一個空穴，它的形成可以參照下圖：
當矽晶體中摻入其他的雜質，如硼、磷等，當摻入硼時，矽晶體中就會存在著一個空穴，它的形成可以參照下圖：
圖中，正電荷表示矽原子，負電荷表示圍繞在矽原子旁邊的四個電子。而黃色的表示摻入的硼原子，因為硼原子周圍只有3個電子，所以就會產生入圖所示的藍色的空穴，這個空穴因為沒有電子而變得很不穩定，容易吸收電子而中和，形成P（positive）型半導體。
同樣，摻入磷原子以後，因為磷原子有五個電子，所以就會有一個電子變得非常活躍，形成N（negative）型半導體。黃色的為磷原子核，紅色的為多餘的電子。如下圖。
同樣，摻入磷原子以後，因為磷原子有五個電子，所以就會有一個電子變得非常活躍，形成N（negative）型半導體。黃色的為磷原子核，紅色的為多餘的電子。如下圖。
N型半導體中含有較多的空穴，而P型半導體中含有較多的電子，這樣，當P型和N型半導體結合在一起時，就會在接觸面形成電勢差，這就是PN結。
當P型和N型半導體結合在一起時，在兩種半導體的交界面區域裏會形成一個特殊的薄層)，介面的P型一側帶負電，N型一側帶正電。這是由於P型半導體多空穴，N型半導體多自由電子，出現了濃度差。N區的電子會擴散到P區，P區的空穴會擴散到N區，一旦擴散就形成了一個由N指向P的“內電場”，從而阻止擴散進行。達到平衡後，就形成了這樣一個特殊的薄層形成電勢差，這就是PN結.
當晶片受光後，PN結中，N型半導體的空穴往P型區移動，而P型區中的電子往N型區移動，從而形成從N型區到P型區的電流。然後在PN結中形成電勢差，這就形成了電源。(如下圖所示）
由於半導體不是電的良導體，電子在通過p－n結後如果在半導體中流動，電阻非常大，損耗也就非常大。但如果在上層全部塗上金屬，陽光就不能通過，電流就不能產生，因此一般用金屬網格覆蓋p－n結（如圖 梳狀電極），以增加入射光的面積。
另外矽表面非常光亮，會反射掉大量的太陽光，不能被電池利用。為此，科學家們給它塗上了一層反射係數非常小的保護膜（如圖），將反射損失減小到5％甚至更小。一個電池所能提供的電流和電壓畢竟有限，於是人們又將很多電池（通常是36個）並聯或串聯起來使用，形成太陽能光電板。
另外矽表面非常光亮，會反射掉大量的太陽光，不能被電池利用。為此，科學家們給它塗上了一層反射係數非常小的保護膜（如圖），將反射損失減小到5％甚至更小。一個電池所能提供的電流和電壓畢竟有限，於是人們又將很多電池（通常是36個）並聯或串聯起來使用，形成太陽能光電板。
2．矽太陽能電池的生產流程
通常的晶體矽太陽能電池是在厚度350～450μm的高品質矽片上製成的，這種矽片從提拉或澆鑄的矽錠上鋸割而成。
上述方法實際消耗的矽材料更多。為了節省材料，目前製備多晶矽薄膜電池多採用化學氣相沉積法，包括低壓化學氣相沉積（LPCVD）和等離子增強化學氣相沉積（PECVD）工藝。此外，液相外延法（LPPE）和濺射沉積法也可用來製備多晶矽薄膜電池。
化學氣相沉積主要是以SiH2Cl2、SiHCl3、SiCl4或SiH4,為反應氣體,在一定的保護氣氛下反應生成矽原子並沉積在加熱的襯底上，襯底材料一般選用Si、SiO2、Si3N4等。但研究發現，在非矽襯底上很難形成較大的晶粒，並且容易在晶粒間形成空隙。解決這一問題辦法是先用 LPCVD在襯底上沉積一層較薄的非晶矽層，再將這層非晶矽層退火，得到較大的晶粒，然後再在這層籽晶上沉積厚的多晶矽薄膜，因此，再結晶技術無疑是很重要的一個環節，目前採用的技術主要有固相結晶法和中區熔再結晶法。多晶矽薄膜電池除採用了再結晶工藝外，另外採用了幾乎所有制備單晶矽太陽能電池的技術，這樣制得的太陽能電池轉換效率明顯提高。
三、納米晶化學太陽能電池
在太陽能電池中矽系太陽能電池無疑是發展最成熟的，但由於成本居高不下，遠不能滿足大規模推廣應用的要求。為此，人們一直不斷在工藝、新材料、電池薄膜化等方面進行探索，而這當中新近發展的納米TiO2晶體化學能太陽能電池受到國內外科學家的重視。
以染料敏化納米晶體太陽能電池（DSSCs）為例，這種電池主要包括鍍有透明導電膜的玻璃基底，染料敏化的半導體材料、對電極以及電解質等幾部分。
如圖所示，白色小球表示TiO2，紅色小球表示染料分子。染料分子吸收太陽光能躍遷到激發態，激發態不穩定，電子快速注入到緊鄰的TiO2導帶，染料中失去的電子則很快從電解質中得到補償，進入TiO2導帶中的電於最終進入導電膜,然後通過外回路產生光電流。
納米晶TiO2太陽能電池的優點在於它廉價的成本和簡單的工藝及穩定的性能。其光電效率穩定在10％以上，製作成本僅為矽太陽電池的1/5～1/10．壽命能達到20年以上。但由於此類電池的研究和開發剛剛起步，估計不久的將來會逐步走上市場。
陽極：染料敏化半導體薄膜（TiO2膜）
陰極：鍍鉑的導電玻璃
電解質：I3-/I-
染料電池應用模型:
1.製作二氧化鈦膜
(1)先把二氧化鈦粉末放入研缽中與粘合劑進行研磨
(2)接著用玻璃棒緩慢地在導電玻璃上進行塗膜
(3)把二氧化鈦膜放入酒精燈下燒結10～15分鐘，然後冷卻
2.利用天然染料為二氧化鈦著色
如圖所示，把新鮮的或冰凍的黑梅、山梅、石榴籽或紅茶，加一湯匙的水並進行擠壓，然後把二氧化鈦膜放進去進行著色，大約需要5分鐘，直到膜層變成深紫色，如果膜層兩面著色的不均勻，可以再放進去浸泡5分鐘，然後用乙醇沖洗，並用柔軟的紙輕輕地擦幹。
3.製作正電極
由染料著色的TiO2為電子流出的一極（即負極）。正電極可由導電玻璃的導電面（塗有導電的SnO2膜層）構成，利用一個簡單的萬用表就可以判斷玻璃的那一面是可以導電的，利用手指也可以做出判斷，導電面較為粗糙。如圖所示，把非導電面標上‘+’，然後用鉛筆在導電面上均勻地塗上一層石墨。
4.加入電解質
利用含碘離子的溶液作為太陽能電池的電解質，它主要用於還原和再生染料。如圖所示，在二氧化鈦膜表面上滴加一到兩滴電解質即可。
5.組裝電池
把著色後的二氧化鈦膜面朝上放在桌上，在膜上面滴一到兩滴含碘和碘離子的電解質，然後把正電極的導電面朝下壓在二氧化鈦膜上。把兩片玻璃稍微錯開，用兩個夾子把電池夾住，兩片玻璃暴露在外面的部分用以連接導線。這樣，你的太陽能電池就做成了。
6.電池的測試
在室外太陽光下，檢測你的太陽能電池是否可以產生電流。
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