TWI473289B - Method of making a solar cell - Google Patents

Method of making a solar cell Download PDF

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TWI473289B
TWI473289B TW100134086A TW100134086A TWI473289B TW I473289 B TWI473289 B TW I473289B TW 100134086 A TW100134086 A TW 100134086A TW 100134086 A TW100134086 A TW 100134086A TW I473289 B TWI473289 B TW I473289B
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substrate
solar cell
group iii
cell according
layer
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TW100134086A
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TW201314941A (en
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Heng Liu
Pei Yun Kuo
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Pinecone En Inc
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Priority to PCT/US2012/045697 priority patent/WO2013043250A1/en
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier
    • H01L31/072Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type
    • H01L31/0735Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type comprising only AIIIBV compound semiconductors, e.g. GaAs/AlGaAs or InP/GaInAs solar cells
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/184Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP
    • H01L31/1844Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP comprising ternary or quaternary compounds, e.g. Ga Al As, In Ga As P
    • H01L31/1848Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP comprising ternary or quaternary compounds, e.g. Ga Al As, In Ga As P comprising nitride compounds, e.g. InGaN, InGaAlN
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/184Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP
    • H01L31/1852Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP comprising a growth substrate not being an AIIIBV compound
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/184Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP
    • H01L31/1856Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP comprising nitride compounds, e.g. GaN
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy
    • Y02E10/544Solar cells from Group III-V materials
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50Manufacturing or production processes characterised by the final manufactured product

Description

太陽能電池的製造方法 Solar cell manufacturing method

本發明係有關一種太陽能電池,特別是關於一種使用雷射以製造聚集式光電池(CPV)的方法。 The present invention relates to a solar cell, and more particularly to a method of using a laser to fabricate a concentrated photovoltaic cell (CPV).

電源可由多種方式產生,例如核能發電、風力發電、水力發電、火力發電或太陽能發電等。電源的選擇必需考量各種因素,例如安全性、成本、對環境的影響、生命期、來源的取得等。近來,綠能源特別受到重視,例如太陽能、地熱(geothermal)能、水力能等,其中,太陽能由於來源的取得容易且不會造成環境的污染,因此特別受到重視。 Power can be generated in a variety of ways, such as nuclear power generation, wind power, hydropower, thermal power, or solar power. The choice of power supply must consider various factors such as safety, cost, impact on the environment, lifetime, and source. Recently, green energy has been particularly valued, such as solar energy, geothermal energy, and hydropower. Among them, solar energy is particularly valued because it is easy to obtain from the source and does not cause environmental pollution.

太陽能電源的產生方式,最常見的有以下兩種:太陽熱(solar thermal)方式及光電(photovoltaic)方式。其中,太陽熱方式係使用太陽的熱能來進行加熱或產生電力;光電方式則是利用光電效應(photovoltaic effect),使用太陽能電池(solar cell)將光輻射直接轉換為電力。 The most common types of solar power generation are solar thermal and photovoltaic. Among them, the solar thermal method uses the thermal energy of the sun to heat or generate electricity; the photoelectric method uses a photovoltaic effect to directly convert the optical radiation into electricity using a solar cell.

目前所使用的太陽能電池最主要有以下兩種:大面積光電板(bulky panel photovoltaic)及聚集式光電池(concentrated photovoltaic,CPV)。大面積光電板又稱為矽基(silicon-based)太陽能電池,其主動層 (active layer)一般係使用矽晶圓或薄膜,其中,矽晶圓可為單晶矽(monocrystalline silicon)、多晶矽(multicrystalline silicon)或帶狀矽(ribbon silicon);薄膜可為碲化鎘(cadium telluride,CdTe)、銅銦鎵硒(copper indium gallium selenide,CIGS)或非晶矽(amorphous silicon,A-Si)。大面積光電板的結構簡單,且不需額外使用光學元件,但是轉換效率偏低(8~10%),因此整體系統成本為中間等級,一般約為US$6/Wp,其中Wp為峰值瓦特。 Currently, there are two main types of solar cells used: bulky panel photovoltaics and concentrated photovoltaics (CPV). Large-area photovoltaic panels are also known as silicon-based solar cells, and active layers are generally made of germanium wafers or thin films, wherein the germanium wafers can be monocrystalline silicon or polycrystalline germanium ( Multicrystalline silicon) or ribbon silicon; the film may be a cadmium telluride (CdTe), a copper indium gallium selenide (CIGS) or an amorphous silicon (A-Si). The large-area photovoltaic panel has a simple structure and does not require additional optical components, but the conversion efficiency is low (8-10%), so the overall system cost is intermediate, generally about US$6/W p , where W p is the peak. watt.

聚集式光電池又稱為化合物基(chemical compound-based)太陽能電池,其主動層一般係使用III-V族化合物,例如砷化鎵(GaAs)、砷化銦鎵(InXGa1-XAs)、磷化鋁(AlP)或磷化鎵(GaP)。第一圖顯示傳統聚集式光電池的結構剖面圖,其由下而上依序包含基板10、砷化鎵(GaAs)層11、砷化銦鎵(InGaAs,InXGa1-XAs)層12、磷化鎵(GaP)層13及磷化鋁(AlP)層14。 Aggregated photovoltaic cells, also known as chemical compound-based solar cells, typically use a III-V compound such as gallium arsenide (GaAs) or indium gallium arsenide (In X Ga 1-X As) as the active layer. , aluminum phosphide (AlP) or gallium phosphide (GaP). The first figure shows a structural cross-sectional view of a conventional concentrating photovoltaic cell, which sequentially includes a substrate 10, a gallium arsenide (GaAs) layer 11, and an indium gallium arsenide (InGaAs, In X Ga 1-X As) layer 12 from bottom to top. , a gallium phosphide (GaP) layer 13 and an aluminum phosphide (AlP) layer 14 .

上述化合物的能帶間隙(band gap)範圍極為狹窄,一般介於0.36~2.45電子伏(eV)之間。下表一列示該些化合物的能帶間隙值: The band gap of the above compounds is extremely narrow, generally ranging from 0.36 to 2.45 electron volts (eV). The energy band gap values for these compounds are listed in Table 1 below:

如第二圖所示的能帶(energy band)圖,當太陽電池吸收的 光能量遠超過最大能帶間隙(2.45電子伏)Eg所對應的能量時,電子20從價帶(valence band)Ev被光能量過激發(over excite)至導帶(conduction band)Ec以上,當電子20返回導帶Ec時,即會產生熱能。如此不但浪費了光能量,且還需額外使用冷卻系統或散熱裝置以排放所產生的熱能。 Energy band diagram as shown in the second figure, when the solar cell absorbs When the light energy far exceeds the energy corresponding to the maximum energy band gap (2.45 electron volts) Eg, the electron 20 is overexcited from the valence band Ev by the light energy to the conduction band Ec. When the electron 20 returns to the conduction band Ec, heat energy is generated. This not only wastes light energy, but also requires additional cooling systems or heat sinks to dissipate the heat generated.

上述化合物大部分為有毒物質且材質易碎,因此增加製造成本或者無法提高良率(yield)。此外,第一圖所示傳統太陽能電池所使用的砷化鎵(GaAs),其對於缺陷密度的容忍度僅為103/cm2,因此也會影響到良率。上述化合物的形成一般係使用昂貴的有機金屬化學氣相沈積法(MOCVD),由於其通常無法沈積的夠厚,因而侷限了太陽電池的轉換效能。再者,傳統聚集式光電池的製程溫度較高(>500℃),因而提高製造成本。 Most of the above compounds are toxic substances and the materials are brittle, thus increasing manufacturing costs or failing to improve yield. In addition, the gallium arsenide (GaAs) used in the conventional solar cell shown in the first figure has a tolerance to defect density of only 10 3 /cm 2 and thus also affects the yield. The formation of the above compounds is generally carried out using expensive organometallic chemical vapor deposition (MOCVD), which limits the conversion efficiency of solar cells due to their generally inability to deposit thick enough. Moreover, the conventional assembly type photovoltaic cell has a high process temperature (>500 ° C), thereby increasing the manufacturing cost.

相較於大面積光電板,聚集式光電池的尺寸較小且轉換效率(25~45%)較高,但是必需額外使用光學元件以進行聚光(例如使用1:1000面積比值的透鏡)以及使用前述的冷卻系統或散熱裝置,因此整體系統成本較高,一般約為US$10/WpCompared to large-area photovoltaic panels, the size of the concentrating photocell is small and the conversion efficiency (25~45%) is high, but additional optical components must be used for concentrating (for example, using a 1:1000 area ratio lens) and The aforementioned cooling system or heat sink, so the overall system cost is high, typically about US$10/W p .

由於傳統聚集式光電池的轉換效率無法有效提高,且整體系統成本無法進一步降低,因此亟需提出一種新穎的太陽能電池,用以改善傳統聚集式光電池的效能。 Since the conversion efficiency of the conventional concentrating photovoltaic cell cannot be effectively improved, and the overall system cost cannot be further reduced, it is urgent to propose a novel solar cell to improve the performance of the conventional concentrating photovoltaic cell.

鑑於上述,本發明實施例的目的之一在於提出一種太陽能電池的製造方法,其使用III族氮化物以取代傳統的III-V族化合物,且使用低溫化學氣 相沈積法或物理氣相沈積法以取代傳統有機金屬化學氣相沈積法(MOCVD),並使用雷射作為反應時的激發能。藉此,本實施例的太陽能電池可提高轉換效能,降低尺寸,且使用低溫製程以降低整體系統成本。 In view of the above, one of the objects of embodiments of the present invention is to provide a method for fabricating a solar cell using a group III nitride in place of a conventional III-V compound and using a low temperature chemical gas. Phase deposition or physical vapor deposition replaces conventional organometallic chemical vapor deposition (MOCVD) and uses laser as the excitation energy for the reaction. Thereby, the solar cell of the present embodiment can improve conversion efficiency, reduce size, and use a low temperature process to reduce overall system cost.

根據本發明實施例,首先提供一底材,且形成一基板於底材的表面。在一實施例中,底材/基板的材質為鋁/氧化鋁。接著,選擇性形成一緩衝層於基板上。沈積複數III族氮化物(III-nitride)層於基板或緩衝層上,其中該些III族氮化物層於沈積時係使用雷射作為反應時的激發能,且該些III族氮化物層的能帶間隙(band gap)值從靠近基板開始依序遞增。其中該底材為鋁底材,該基板為氧化鋁(Al2O3)基板,且氧化鋁基板係藉由硬式陽極處理(hard-anodizing)鋁底材所形成。 According to an embodiment of the invention, a substrate is first provided and a substrate is formed on the surface of the substrate. In one embodiment, the material of the substrate/substrate is aluminum/alumina. Next, a buffer layer is selectively formed on the substrate. Depositing a plurality of III-nitride layers on the substrate or the buffer layer, wherein the group III nitride layers are deposited using a laser as an excitation energy during the reaction, and the group III nitride layers are The band gap value is sequentially increased from the vicinity of the substrate. Wherein the substrate is an aluminum substrate, the substrate is an alumina (Al 2 O 3 ) substrate, and the alumina substrate is formed by a hard-anodizing aluminum substrate.

10‧‧‧基板 10‧‧‧Substrate

11‧‧‧砷化鎵(GaAs)層 11‧‧‧ gallium arsenide (GaAs) layer

12‧‧‧砷化銦鎵(InGaAs)層 12‧‧‧Indium gallium arsenide (InGaAs) layer

13‧‧‧磷化鎵(GaP)層 13‧‧‧Gallium phosphide (GaP) layer

14‧‧‧磷化鋁(AlP)層 14‧‧‧Aluminum phosphide (AlP) layer

20‧‧‧電子 20‧‧‧Electronics

30‧‧‧底材 30‧‧‧Substrate

31‧‧‧基板 31‧‧‧Substrate

32‧‧‧緩衝層(GaN) 32‧‧‧ Buffer Layer (GaN)

33A‧‧‧氮化銦(InN) 33A‧‧‧Indium nitride (InN)

33B‧‧‧氮化銦鎵(InGaN) 33B‧‧‧Indium Gallium Nitride (InGaN)

33C‧‧‧氮化銦鋁鎵(InAlGaN) 33C‧‧‧Indium Gallium Nitride (InAlGaN)

33D‧‧‧氮化鋁(AlN) 33D‧‧‧Aluminum Nitride (AlN)

Ev‧‧‧價帶 Ev‧‧‧Price Belt

Ec‧‧‧導帶 Ec‧‧‧ Guide belt

Eg‧‧‧能帶間隙 Eg‧‧‧ with gap

第一圖顯示傳統聚集式光電池的結構剖面圖。 The first figure shows a structural cross-sectional view of a conventional concentrating photovoltaic cell.

第二圖顯示能帶(energy band)圖。 The second image shows the energy band diagram.

第三A圖至第三C圖的剖面圖顯示本發明實施例之太陽能電池的製造方法及結構。 The cross-sectional views of the third to third C diagrams show the manufacturing method and structure of the solar cell of the embodiment of the present invention.

第四圖顯示本實施例之太陽能電池結構及其對應的太陽光波長。 The fourth figure shows the structure of the solar cell of this embodiment and its corresponding wavelength of sunlight.

第三A圖至第三C圖的剖面圖顯示本發明實施例之太陽能電池(solar cell,又稱為photovoltaic cell或photoelectric cell)的製造方法及結構。太陽能電池可用以將光能(例如太陽光能)轉換為電能。圖式僅顯示出 與本實施例相關的組成要件,因此,所示層級之間可視實際應用需求而插入其他額外層級。此外,圖式中各組成要件的尺寸並未依實際比例繪製。 The cross-sectional views of the third embodiment to the third C show the manufacturing method and structure of a solar cell (also referred to as a photovoltaic cell or a photoelectric cell) according to an embodiment of the present invention. Solar cells can be used to convert light energy (eg, solar energy) into electrical energy. The schema only shows The constituent elements related to the present embodiment, therefore, other additional levels can be inserted between the illustrated levels depending on actual application requirements. In addition, the dimensions of the various components in the drawings are not drawn to scale.

根據本發明實施例之一,如第三A圖所示,提供矽(silicon,Si)底材30。接著,於矽底材30的表面形成碳化矽(silicon carbide,SiC)基板31。在一較佳實施例中,碳化矽基板31的厚度大約為2~10微米(μm),但不限定於此。關於碳化矽基板31的形成方法可參考Udagawa等人所提出的美國專利公開第2009/0045412號,題為“Method for Production of Silicon Carbide Layer,Gallium Nitride Semiconductor device and Silicon Substrate”,其內容可視為本說明書的一部份。 According to one of the embodiments of the present invention, as shown in FIG. 3A, a silicon (Si) substrate 30 is provided. Next, a silicon carbide (SiC) substrate 31 is formed on the surface of the tantalum substrate 30. In a preferred embodiment, the thickness of the tantalum carbide substrate 31 is approximately 2 to 10 micrometers (μm), but is not limited thereto. For a method of forming the tantalum carbide substrate 31, reference is made to U.S. Patent Publication No. 2009/0045412, entitled "Method for Production of Silicon Carbide Layer, Gallium Nitride Semiconductor device and Silicon Substrate". Part of the manual.

根據本發明實施例之二,第三A圖結構的形成方法如下所述。首先,提供鋁(aluminum,Al)底材30。接著,對鋁底材30進行硬式陽極處理(hard-anodizing),因而於鋁底材30的表面形成氧化鋁(aluminum oxide,Al2O3)基板31。氧化鋁一般又稱為藍寶石(sapphire),其較未處理過的鋁來得堅硬。在一較佳實施例中,氧化鋁基板31的厚度大約為2~10微米(μm),但不限定於此。 According to the second embodiment of the present invention, the method of forming the structure of the third A is as follows. First, an aluminum (Al) substrate 30 is provided. Next, the aluminum substrate 30 is subjected to hard-anodizing, whereby an aluminum oxide (Al 2 O 3 ) substrate 31 is formed on the surface of the aluminum substrate 30. Alumina is also commonly referred to as sapphire, which is harder than untreated aluminum. In a preferred embodiment, the thickness of the alumina substrate 31 is approximately 2 to 10 micrometers (μm), but is not limited thereto.

陽極氧化處理(anodizing)係為一種電解(electrolytic)製程,將待處理金屬浸於酸液(例如硫酸(sulfuric acid))中並通以電流。關於陽極氧化處理的技術細節可參考Chang等人所提出的美國專利公開第2011/0146795號,題為“Structure and Preparation of CIGS-Based Solar Cells Using an Anodized Substrate with an Alkali Metal Precursor”,其內容可視為本說明書的一部份。本實施例使用的硬式陽極處理和一般陽極氧化處理的主要差別在於,硬式陽極處理的溫度較低於一般陽極氧化處理的溫度,且 通過的電流較一般陽極氧化處理來得高。經硬式陽極處理所形成的氧化鋁基板31,其表面具晶粒介面(grain boundary),且其晶體具單一方位(single orientation),例如C平面(C-plane)或A平面(A-plane)。 Anodizing is an electrolytic process in which a metal to be treated is immersed in an acid solution such as sulfuric acid and passed through an electric current. For details of the technique of the anodizing treatment, refer to US Patent Publication No. 2011/0146795, entitled "Structure and Preparation of CIGS-Based Solar Cells Using an Anodized Substrate with an Alkali Metal Precursor", the contents of which are visible. This is part of this manual. The main difference between the hard anodizing and the general anodizing treatment used in this embodiment is that the temperature of the hard anode treatment is lower than the temperature of the general anodizing treatment, and The current passed is higher than that of the general anodizing treatment. The alumina substrate 31 formed by the hard anodization has a grain boundary on its surface, and its crystal has a single orientation, such as a C-plane or an A-plane. .

接著,如第三B圖所示,形成緩衝層32於基板31上。在本說明書中,方向“上”係指遠離底材30的方向,亦即靠近光源的方向;方向“下”係指靠近底材30的方向。緩衝層32係用以調節後續層級與基板31之間的應力(stress)。本實施例使用氮化鎵(gallium nitride,GaN)作為緩衝層32的材質,其可使用(但不限定於)一般化學氣相沈積法(chemical vapor deposition,CVD)以沈積於基板31上。本實施例所使用的氮化鎵(GaN)對於缺陷密度(defect density)的容忍度可達109/cm2,然而,傳統太陽能電池所使用的砷化鎵(gallium arsenide,GaAs),其對於缺陷密度的容忍度僅為103/cm2。本實施例雖形成緩衝層32於基板31上,然而,也可省略緩衝層32的形成。 Next, as shown in FIG. B, a buffer layer 32 is formed on the substrate 31. In the present specification, the direction "upper" refers to the direction away from the substrate 30, that is, the direction close to the light source; the direction "down" refers to the direction near the substrate 30. The buffer layer 32 is used to adjust the stress between the subsequent level and the substrate 31. In this embodiment, gallium nitride (GaN) is used as the material of the buffer layer 32, which can be deposited on the substrate 31 using, but not limited to, general chemical vapor deposition (CVD). The gallium nitride (GaN) used in this embodiment has a tolerance of 10 9 /cm 2 for defect density. However, gallium arsenide (GaAs) used in conventional solar cells is The defect density tolerance is only 10 3 /cm 2 . In the present embodiment, the buffer layer 32 is formed on the substrate 31. However, the formation of the buffer layer 32 may be omitted.

如第三C圖所示,形成複數III族氮化物(group III-nitride)層33A~33D於緩衝層32上。換句話說,每一III族氮化物層33A~33D包含氮原子以及至少一種III族原子(例如鋁、鎵(gallium)、銦(indium)等)。以第三C圖所示為例,該些III族氮化物層33A~33D從下(靠近基板31)而上(遠離基板31)分別為氮化銦(indium nitride,InN)33A、氮化銦鎵(indium gallium nitride,InGaN,InXGa1-XN)33B、氮化銦鋁鎵(indium aluminum gallium nitride,InAlGaN)33C及氮化鋁(aluminum nitride,AlN)33D。 As shown in the third C diagram, a plurality of group III-nitride layers 33A to 33D are formed on the buffer layer 32. In other words, each of the group III nitride layers 33A to 33D contains a nitrogen atom and at least one group III atom (for example, aluminum, gallium, indium, etc.). Taking the third C diagram as an example, the III-nitride layers 33A to 33D are indium nitride (InN) 33A and indium nitride from the bottom (near the substrate 31) and away from the substrate 31. Indium gallium nitride (InGaN, In X Ga 1-X N) 33B, indium aluminum gallium nitride (InAlGaN) 33C, and aluminum nitride (AlN) 33D.

根據本實施例的特徵之一,該些III族氮化物層33A~33D的能帶 間隙(band gap)值從下而上依序遞增。下表二列示該些III族氮化物層33A~33D的能帶間隙值: According to one of the features of the embodiment, the band gap values of the group III nitride layers 33A to 33D are sequentially increased from bottom to top. The energy band gap values of the III-nitride layers 33A to 33D are listed in Table 2 below:

第四圖顯示本實施例之太陽能電池結構及其對應的太陽光波長。根據E=h*(c/λ),波長λ與光能量E成反比,其中h為普朗克(Planck)常數,c為光速。根據本實施例的結構,能帶間隙值愈大者愈靠近光源(例如太陽光源)處,藉此,當電子從價帶(valence band)被光能量激發至導帶(conduction band)時,可避免(或減少)電子因過激發(over excite)所產生的無謂熱能。反觀傳統太陽能電池,其最大能帶間隙值僅為2.45電子伏,因此,大於該數值所對應的光能量會產生電子的過激發而產生無謂的熱能。 The fourth figure shows the structure of the solar cell of this embodiment and its corresponding wavelength of sunlight. According to E = h * (c / λ), the wavelength λ is inversely proportional to the light energy E, where h is the Planck constant and c is the speed of light. According to the structure of the present embodiment, the larger the band gap value is, the closer it is to the light source (for example, the sun light source), whereby when the electron is excited from the light energy to the conduction band by the valence band, Avoid (or reduce) the unnecessary heat generated by electrons due to over excite. In contrast, the traditional solar cell has a maximum band gap value of only 2.45 eV. Therefore, the light energy corresponding to this value produces over-excitation of electrons and generates unnecessary heat energy.

根據第四圖及表二所示,由於本實施例之太陽能電池的結構具有較寬廣的能帶間隙範圍,亦即0.7~6.3電子伏,因此可以對應至較寬廣的光能量(或波長)範圍。反觀傳統太陽能電池,其能帶間隙的範圍較窄,例如0.36~2.45電子伏,因此對應的光能量(或波長)範圍較窄。如前所述,對於較大的光能量(或較小波長),會造成電子的過激發而產生無謂的熱 能。因此,本實施例的太陽能電池之(光轉電)轉換效能遠大於傳統太陽能電池的轉換效能。此外,本實施例的緩衝層32(GaN)具有3.4電子伏的能帶間隙,上述碳化矽(SiC)基板31具有2.86電子伏的能帶間隙,也有助於轉換效率的提升。例如,當一部份的光能量未被III族氮化物層33A~33D吸收時,則仍可由緩衝層32及碳化矽基板31加以吸收。根據粗略的估算,本實施例的轉換效能可大於60%,而傳統太陽能電池僅能達到45%。除了具有較寬廣的能帶間隙範圍外,本實施例因使用III族氮化物,相較於傳統太陽能電池的材質,本實施例具有較多的材質組合搭配可能性,而可形成較多層級數,此也有助於整體轉換效率的改善。 According to the fourth figure and the second table, since the structure of the solar cell of the embodiment has a wide band gap range, that is, 0.7 to 6.3 electron volts, it can correspond to a wide range of light energy (or wavelength). . In contrast, conventional solar cells have a narrow band gap, for example, 0.36 to 2.45 eV, so the corresponding range of light energy (or wavelength) is narrow. As mentioned earlier, for larger light energies (or smaller wavelengths), over-excitation of electrons can result in unwanted heat. can. Therefore, the (light-to-electricity) conversion efficiency of the solar cell of the present embodiment is much greater than that of the conventional solar cell. Further, the buffer layer 32 (GaN) of the present embodiment has an energy band gap of 3.4 electron volts, and the above-described silicon carbide (SiC) substrate 31 has an energy band gap of 2.86 electron volts, which also contributes to an improvement in conversion efficiency. For example, when a portion of the light energy is not absorbed by the group III nitride layers 33A to 33D, it can be absorbed by the buffer layer 32 and the tantalum carbide substrate 31. According to a rough estimate, the conversion efficiency of this embodiment can be greater than 60%, while the conventional solar cell can only reach 45%. In addition to having a wide range of band gaps, this embodiment uses a group III nitride, and this embodiment has more material combinations and possibilities than the material of a conventional solar cell, and more layers can be formed. This also contributes to the improvement of overall conversion efficiency.

根據本發明實施例之三,該些III族氮化物層33A~33D可使用化學氣相沈積法(CVD)且使用雷射作為反應時的激發能。本實施例可使用雷射光作為激發能,實施熱分解(pyrolytic)以進行熱化分解(thermochemical decomposition)反應,用以將反應氣體分解後再結合而形成所要沈積的薄膜。本實施例也可使用雷射光作為激發能,實施光分解(photolytic)以進行光化(photochemical)反應,用以將反應氣體分解後再結合而形成所要沈積的薄膜。關於熱分解及光分解的技術細節可參考Narula等人所提出的美國專利第5,417,823號,題為“Metal-Nitrides Prepared by Photolytic/Pyrolytic decomposition of Metal-Amides”,其內容可視為本說明書的一部份。 According to the third embodiment of the present invention, the group III nitride layers 33A to 33D may use chemical vapor deposition (CVD) and use laser as the excitation energy in the reaction. In the present embodiment, laser light can be used as the excitation energy, and pyrolytic can be performed to carry out a thermal chemical decomposition reaction for decomposing the reaction gas and then combining to form a film to be deposited. In this embodiment, laser light can also be used as the excitation energy, and photolytic is carried out to carry out a photochemical reaction for decomposing the reaction gas and then combining to form a film to be deposited. For a detailed description of the thermal decomposition and the photodecomposition, see U.S. Patent No. 5,417,823, to the name of "Metal-Nitrides Prepared by Photolytic/Pyrolytic decomposition of Metal-Amides", which may be considered as a part of this specification. Share.

下表三例示(但不限定)本實施例於進行化學氣相沈積法時可使用的反應氣體源(reactant):表三 Table 3 below exemplifies (but does not limit) the reactive gas source (reactant) that can be used in the chemical vapor deposition method of this embodiment: Table 3

除了實施例三所述的化學氣相沈積法,該些III族氮化物層33A~33D的形成也可使用物理氣相沈積法(physical vapor deposition,PVD)。相較於化學氣相沈積法,物理氣相沈積法通常使用較低溫度及壓力(例如真空),首先將所要沈積薄膜的元素或化合物予以氣化或蒸發(vaporized),經沈澱凝結(condensation)後,於視線範圍(line of sight)內形成薄膜。關於使用物理氣相沈積法以形成III族氮化物層的技術細節可參考Nagai等人所提出的美國專利第6,716,655號,題為“Group III Nitride Compound Semiconductor Element and Method for Producing the Same”,其內容可視為本說明書的一部份。 In addition to the chemical vapor deposition method described in the third embodiment, the formation of the group III nitride layers 33A to 33D may also be performed by physical vapor deposition (PVD). Compared to chemical vapor deposition, physical vapor deposition generally uses lower temperatures and pressures (such as vacuum) to first vaporize or vaporize the elements or compounds of the film to be deposited, and to form condensation. Thereafter, a film is formed in the line of sight. For a detailed description of the use of physical vapor deposition to form a group III nitride layer, reference is made to U.S. Patent No. 6,716,655 to Nagai et al., entitled "Group III Nitride Compound Semiconductor Element and Method for Producing the Same", It can be seen as part of this manual.

根據本發明實施例之四,該些III族氮化物層33A~33D的形成可使用脈衝雷射(pulsed laser)沈積法,其為物理氣相沈積法的一種。在本實施例中,使用高功率脈衝雷射束作為激發能,打擊來源物質靶使其氣化,經沈澱凝結後形成薄膜。關於使用雷射作為激發能以沈積氮化物的技術細節可參考A.Perrone所提出的“An Overview on Nitride Film Deposited by Reactive Pulsed Laser Ablation”(Lasers and Electro-Optics Europe,2000,Conference Digest),其內容可視為本說明書的一部份。 According to the fourth embodiment of the present invention, the formation of the group III nitride layers 33A to 33D may be performed by a pulsed laser deposition method which is one of physical vapor deposition methods. In the present embodiment, a high-power pulsed laser beam is used as the excitation energy, the source material target is struck to vaporize, and a film is formed by precipitation and condensation. For details on the use of lasers as excitation energy to deposit nitrides, reference is made to A. Perrone's "An Overview on Nitride Film Deposited by Reactive Pulsed Laser Ablation" (Lasers and Electro-Optics Europe, 2000, Conference Digest), which The content can be considered as part of this manual.

根據上述,本實施例使用雷射作為反應的激發能,相較於傳統 方法(例如,有機金屬化學氣相沈積法(MOCVD)),本實施例可操作於較低溫度(<500℃),因而得以降低熱預算(thermal budget)或成本。此外,相較於有機金屬化學氣相沈積法(MOCVD),本實施例較容易形成較厚的III族氮化物層33A~33D,此也有助於整體轉換效率的改善。 According to the above, this embodiment uses a laser as the excitation energy of the reaction, compared to the conventional Methods such as organometallic chemical vapor deposition (MOCVD), this embodiment can operate at lower temperatures (<500 °C), thereby reducing thermal budget or cost. In addition, this embodiment is easier to form thicker group III nitride layers 33A to 33D than metalorganic chemical vapor deposition (MOCVD), which also contributes to an improvement in overall conversion efficiency.

鑑於上述本實施例因具有較寬廣的能帶間隙範圍、因使用III族氮化物而具有較多的材質組合搭配可能性且容易形成較厚的層級,所以轉換效率遠高於傳統太陽能電池。因此,本實施例可以使用較小尺寸的聚光光學元件,甚至不需要任何聚光光學元件,且可簡化或縮小冷卻系統或散熱裝置的尺寸(亦可不需使用任何冷卻系統),因而得以降低整體太陽能電池的尺寸與成本。除此之外,本發明實施例之太陽能電池因III族氮化物本身的材質特性(較大的缺陷密度容忍度及不易碎)可做成較大尺寸,進而直接提高整體轉換電力。 In view of the fact that the above embodiment has a wider band gap range, has more material combination and combination possibilities due to the use of the group III nitride, and is easy to form a thicker layer, the conversion efficiency is much higher than that of the conventional solar cell. Therefore, the present embodiment can use a smaller size concentrating optical element, even without any concentrating optical element, and can simplify or reduce the size of the cooling system or the heat sink (or no need to use any cooling system), thereby reducing The size and cost of the overall solar cell. In addition, the solar cell of the embodiment of the present invention can be made into a larger size due to the material characteristics (large defect density tolerance and non-fragile) of the group III nitride itself, thereby directly improving the overall conversion power.

以上所述僅為本發明之較佳實施例而已,並非用以限定本發明之申請專利範圍;凡其它未脫離發明所揭示之精神下所完成之等效改變或修飾,均應包含在下述之申請專利範圍內。 The above description is only the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention; all other equivalent changes or modifications which are not departing from the spirit of the invention should be included in the following Within the scope of the patent application.

30‧‧‧底材 30‧‧‧Substrate

31‧‧‧基板 31‧‧‧Substrate

32‧‧‧緩衝層(GaN) 32‧‧‧ Buffer Layer (GaN)

33A‧‧‧氮化銦(InN) 33A‧‧‧Indium nitride (InN)

33B‧‧‧氮化銦鎵(InGaN) 33B‧‧‧Indium Gallium Nitride (InGaN)

33C‧‧‧氮化銦鋁鎵(InAlGaN) 33C‧‧‧Indium Gallium Nitride (InAlGaN)

33D‧‧‧氮化鋁(AlN) 33D‧‧‧Aluminum Nitride (AlN)

Claims (10)

一種太陽能電池的製造方法,包含:提供一底材;形成一基板於該底材的表面;及沈積複數III族氮化物(III-nitride)層於該基板上,其中該些III族氮化物層於沈積時係使用雷射作為反應時的激發能,且該些III族氮化物層的能帶間隙(band gap)值從靠近該基板開始依序遞增;其中該底材為鋁底材,該基板為氧化鋁(Al2O3)基板,且該氧化鋁基板係藉由硬式陽極處理(hard-anodizing)該鋁底材所形成。 A method of manufacturing a solar cell, comprising: providing a substrate; forming a substrate on a surface of the substrate; and depositing a plurality of III-nitride layers on the substrate, wherein the III-nitride layers In the deposition, a laser is used as the excitation energy in the reaction, and the band gap values of the group III nitride layers are sequentially increased from the substrate; wherein the substrate is an aluminum substrate, The substrate is an alumina (Al 2 O 3 ) substrate, and the alumina substrate is formed by hard-anodizing the aluminum substrate. 如申請專利範圍第1項所述太陽能電池的製造方法,其中該氧化鋁基板的表面具晶粒介面,且其晶體具單一方位。 The method for manufacturing a solar cell according to claim 1, wherein the surface of the alumina substrate has a grain interface and the crystal has a single orientation. 如申請專利範圍第1項所述太陽能電池的製造方法,更包含形成一緩衝層於該基板與該些III族氮化物層之間。 The method for manufacturing a solar cell according to claim 1, further comprising forming a buffer layer between the substrate and the group III nitride layers. 如申請專利範圍第3項所述太陽能電池的製造方法,其中該緩衝層包含氮化鎵(GaN)。 The method of manufacturing a solar cell according to claim 3, wherein the buffer layer comprises gallium nitride (GaN). 如申請專利範圍第1項所述太陽能電池的製造方法,其中該些III族氮化物層從靠近該基板開始依序至少包含氮化銦(InN)層、氮化銦鎵(InGaN)層、氮化銦鋁鎵(InAlGaN)層及氮化鋁(AlN)層。 The method for fabricating a solar cell according to claim 1, wherein the group III nitride layer comprises at least an indium nitride (InN) layer, an indium gallium nitride (InGaN) layer, and nitrogen from the substrate. Indium aluminum gallium (InAlGaN) layer and aluminum nitride (AlN) layer. 如申請專利範圍第1項所述太陽能電池的製造方法,其中該些III族氮化物層的能帶間隙範圍介於0.7~6.3電子伏。 The method for manufacturing a solar cell according to claim 1, wherein the group III nitride layer has a band gap ranging from 0.7 to 6.3 electron volts. 如申請專利範圍第1項所述太陽能電池的製造方法,其中該些III族氮化物層係以低於500溫度之化學氣相沈積法所沈積。 The method of manufacturing a solar cell according to claim 1, wherein the group III nitride layer is deposited by a chemical vapor deposition method at a temperature lower than 500. 如申請專利範圍第7項所述太陽能電池的製造方法,其中該雷射實施熱分解(pyrolytic)以進行熱化分解(thermochemical decomposition)反應,或者實施光分解(photolytic)以進行光化(photochemical)反應。 The method for producing a solar cell according to claim 7, wherein the laser is subjected to pyrolytic for a thermochemical decomposition reaction or photolytic for photochemical. reaction. 如申請專利範圍第1項所述太陽能電池的製造方法,其中該些III族氮化物層係以物理氣相沈積法所沈積。 The method for fabricating a solar cell according to claim 1, wherein the group III nitride layers are deposited by physical vapor deposition. 如申請專利範圍第9項所述太陽能電池的製造方法,其中該些III族氮化物層之沈積係使用脈衝雷射(pulsed laser)沈積法。 The method of manufacturing a solar cell according to claim 9, wherein the deposition of the group III nitride layer is performed by a pulsed laser deposition method.
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