201251051 六、發明說明： 【發明所屬之技術領域】 本發明涉及一種奈米晶石夕薄膜異質接面太陽能電 池，尤指入光層為奈米晶矽半導體，使該層的能隙提 高，提高開路電壓，也產生更高的轉換效率。 【先前技術】 以η型單晶石夕為基板之高效率a-Si/c-Si之HIT太 陽電池在1994年由Sawada研究團隊提出，接著許多研 究圑隊從事異質接面（Heterojunction with Intrinsic Thin layer; HIT)太陽電池的相關研究，HIT太陽電池是目前 高效率太陽能電池領域中最熱門的研究之一，主要是因 為HIT太陽電池具有極高（〜23°/。)之轉換效率及極低 (〜200eC)之製程溫度。主要以熱燈絲化學氣相沉積法 (Hot wire chemical vapor deposition ; HWCVD)及電漿輔 助化學氣相沈積系統(Plasma enhanced chemical vapor deposition; PECVD)沉積矽膜製造異質接面太陽電池， 其中Sanyo以PECVD製作出世界最高效率23%之異質 接面太陽電池。與單晶太陽電池比較，HIT太陽電池具 下列優點： 1. HIT太陽電池與單晶太陽電池比較，HIT太陽電 池在電池表面有較少的功率損失，因為上電極採用透明 導電膜(ITO)’而單晶太陽電池所產生之電子會在指狀金 屬電極處發生復合損失。 201251051 2. 因為HIT太陽電池在單晶基板上沉積一層非晶 矽薄膜可以有效鈍化單晶表面懸浮鍵缺陷，減少複合損 失，可以改善p_n界面特性，減少功率損失。 3. 在同樣的模組面積下，HIT太陽電池有較高的電 力輸出，以1000 m2面積下，單晶太陽電池模組輸出功 率為127 kW’而HIT太陽電池模組輸出功率為168 kW，足足多出41 kW。 4. 在高溫的環境下，單晶太陽電池模組因溫度升高 使得效率下降，而HIT太陽電池在高溫下(〜7〇Qc)有較 尚的電力輸出，與單晶太陽電池模組比較可以有多出 10%電力輸出。 HI T太陽電池結^合單晶矽太陽電池與薄膜太陽電池 的優點，如高效率、低製程溫度等等，所以在太陽能電 池產業中是極需發展的一種技術。一般而言，單晶矽的 能隙寬度為1.1 eV，光入射至單晶太陽能電池中會有 31 %的熱損失，特別是在短波長的光(uv波段）。而異質 接面太陽電池中n-a_SiC矽膜具有2.leV的寬能隙，可 以減少表面的熱損失。 但上敘技術在沉積寬能隙矽薄膜需摻入碳原子或 氧原子；窄能隙矽薄膜需摻入鍺原子，在製程上有相當 的困難度。 【發明内容】 於是，為解決上述之缺失，本發明之目的係在提供 -種奈米轉薄膜異質接面太陽能電池，❺沉積太陽 201251051 電池入光層提升短波長光譜利用範圍，也利用奈米晶矽 改變材料能隙’有效的提高能隙增加長波長光譜利用範 圍。 本發明之另一目的係在提供一種奈米晶矽薄膜異 質接面太陽能電池，改善目前發展多接面串接太陽電池 製程的困難，有效降低薄膜太陽電池中矽基薄膜厚度， 縮短製程時間，降低生產成本。 為達上述之目的，本發明揭露一種奈米晶矽薄膜異 質接面太陽能電池，其主要包括：一可透光之透明電 極；一背電極；及一光電轉換結構介於前面所述電極 間，所述光電轉換結構包含一個導電型式之第一層的結 晶石夕半導體於該背電極上；第二層係本質非晶矽半導 體；及第三層係導電型式與第一層相反之奈米晶矽半導 體’俾藉奈米晶矽半導體的量子侷限效應有效使第三層 的能隙提高，有效的提高能隙增加長波長光譜利用範 圍’產生更高的轉換效率。 其中’第二層奈米晶石夕半導體之晶粒大小係3ηϊη至 5nm ’第三層奈米晶矽半導體之厚度係5ηιη至i〇mn。 本發明的優點在於，透過做為入光層的第三層係由 奈米晶矽半導體所形成的薄膜，利用奈米晶矽特有之量 子倡限效應（quantum confinement effect)，可將入光層的 能隙提高，提高開路電壓，也因為有效光能隙之增強現 象提高光的吸收範圍，如沉積太陽電池的入光層（p_layer) 提升短波長光譜利用範圍，而奈米晶矽改變材料能隙增 加長波長光譜利用範圍。應用奈米晶矽結構的尺寸大小 201251051 控制吸收的光譜的波長範圍，其量子 " 收的光子能量 大約從L5eV到2.GeV，吸收完的奸能量將轉換成載 子（Carrier)’最後由正負電極兩端將载子傳導出，形 成光轉換之電流。 另’本發明不需如習知異質接面太陽電池中n_a_sic 在沉積寬能隙矽薄膜需摻入碳原子或氧原子，窄能隙石夕 薄膜需摻入鍺原子；本發明只需透過沉積技術：可形 成，可改善目前發展多接面串接太陽電池製程的困難， 有效降低薄膜太陽電池中矽基薄膜厚度，縮短製程時 間，降低生產成本。 【實施方式】 茲有關本發明之詳細内容及技術說明，現以實施例 來作進一步說明，但應瞭解的是，該等實施例僅為例示 說明之用，而不應被解釋為本發明實施之限制。 圖1係為本發明太陽能電池之實施例示意圖。實施 上係由光電轉換結構所組成，第一層為η型結晶矽半導 體1〇為基底作為一個導電類型半導體層，第二層為本 質非晶矽半導體2〇。第三層係導電型式與第一層導電型 式相反之ρ型奈米晶石夕半導體30。銀或銘金屬層形成一 背電極40位於該η型結晶矽半導體10下方’透明電 極50是形成了 ΙΤ〇 (銦錫氧化物）或錫氧化物電極形 成於該第三層之ρ型奈米晶石夕半導體30上方，及銀或 鋁金屬層形成一正面電極6〇於該透明電極50表面。 前述圖1之太陽能電池的製造方法如下。首先，厚 201251051 度小於400/zm的η型結晶矽半導體10在電漿輔助化學 氣相沉積系統(PECVD)，通入SiH4矽曱烷氣體，基板 加熱到大約120°C，打開電漿使SiH4矽曱烷氣體解離開 始沉積矽氫薄膜，如矽烷，即在該内在η型結晶矽半導 體10表面形成小於5 nm的本質非晶矽半導體20。 然後於該本質非晶矽半導體20表面，利用電漿輔 助化學氣相沉積系統（PECVD)，控制氣體流量、電漿 功率等參數，得到一種矽與氫鍵結的奈米顆粒（結晶顆粒 大小可控制在1〜30nm)結晶性介電質薄膜，該類薄膜就 是矽氫為主的氫化奈米晶矽（nc-Si)薄膜，為第三層之 P型奈米晶石夕半導體30，厚度約5nm至1 Onm。 此後，透明電極50採用蒸鍍法、濺鍍法製做任何 已知透明導電膜(TCO)做為太陽能電池的正面電極。 最後，背電極40採用蒸鍍法已知或類似在由形成 η型微晶矽半導體層10背面 圖2為能隙值(Eg)與晶粒大小(L)之關係圖。當該第 三層之P型奈米晶矽半導體30的晶粒大小（L)在5nm以 下時，藉由第三層P型奈米晶矽半導體30材料將會出 現量子侷限效應（quantum confinement effect)，可將第三 層非晶矽半導體層材料能隙提高，與第二層的本質非晶 矽半導體20形成異質接面，提高開路電壓，以本實施 例第三層材料奈米化後能隙從1.7eV提高到2.5eV。201251051 VI. Description of the Invention: [Technical Field] The present invention relates to a nanocrystalline spar film heterojunction solar cell, especially if the light entrance layer is a nanocrystalline semiconductor, so that the energy gap of the layer is improved and improved. The open circuit voltage also produces higher conversion efficiency. [Prior Art] The high-efficiency a-Si/c-Si HIT solar cell with η-type single crystal as the substrate was proposed by the Sawada research team in 1994, and then many research teams engaged in Heterojunction with Intrinsic Thin. HIT) HIT solar cell is one of the most popular research in the field of high-efficiency solar cells, mainly because HIT solar cells have extremely high conversion efficiency (~23°/.) and extremely low Process temperature (~200eC). Heterogeneous junction solar cells are mainly fabricated by hot wire chemical vapor deposition (HWCVD) and plasma enhanced chemical vapor deposition (PECVD) deposition, in which Sanyo is PECVD. Produced the world's highest efficiency 23% heterojunction solar cells. Compared with single-crystal solar cells, HIT solar cells have the following advantages: 1. HIT solar cells have less power loss on the surface of the cell compared to single-crystal solar cells because the upper electrode uses a transparent conductive film (ITO). The electrons generated by the single crystal solar cell undergo a composite loss at the finger metal electrode. 201251051 2. Because HIT solar cells deposit an amorphous germanium film on a single crystal substrate, it can effectively passivate the surface floating bond defects of the single crystal and reduce the composite loss, which can improve the p_n interface characteristics and reduce power loss. 3. Under the same module area, HIT solar cells have higher power output. With 1000 m2 area, the output power of single crystal solar cell module is 127 kW' and the output power of HIT solar cell module is 168 kW. A full 41 kW. 4. In a high temperature environment, the single crystal solar cell module has a lower efficiency due to the increase in temperature, while the HIT solar cell has a higher power output at a high temperature (~7〇Qc), compared with a monocrystalline solar cell module. There can be an extra 10% power output. HI T solar cells combine the advantages of single crystal germanium solar cells and thin film solar cells, such as high efficiency, low process temperature, etc., so they are a technology that needs to be developed in the solar cell industry. In general, single crystal germanium has a band gap of 1.1 eV, and light incident on a single crystal solar cell has a heat loss of 31%, especially in short wavelength light (uv band). In the heterojunction solar cell, the n-a_SiC ruthenium film has a wide energy gap of 2.leV, which can reduce the heat loss of the surface. However, the above-mentioned techniques require the incorporation of carbon atoms or oxygen atoms in the deposition of a wide-gap film; the narrow-gap film needs to be doped with germanium atoms, which is quite difficult in the process. SUMMARY OF THE INVENTION Accordingly, in order to solve the above-mentioned drawbacks, the object of the present invention is to provide a nano-transfer film heterojunction solar cell, which is used to enhance the short-wavelength spectrum utilization range of the solar cell, and also utilizes nanometers. The crystal lattice changes the energy gap of the material to effectively increase the energy gap and increase the utilization range of the long wavelength spectrum. Another object of the present invention is to provide a nanocrystalline germanium film heterojunction solar cell, which improves the current difficulty in developing a multi-joint tandem solar cell process, effectively reduces the thickness of the germanium-based film in the thin film solar cell, and shortens the process time. reduce manufacturing cost. In order to achieve the above object, the present invention discloses a nanocrystalline germanium film heterojunction solar cell, which mainly comprises: a transparent electrode capable of transmitting light; a back electrode; and a photoelectric conversion structure interposed between the electrodes. The photoelectric conversion structure comprises a first layer of a crystalline type of a semiconductor layer on the back electrode; a second layer of an intrinsic amorphous germanium semiconductor; and a third layer of a conductive pattern opposite to the first layer of the nanocrystal The quantum confinement effect of the semiconductor semiconductor is effective to increase the energy gap of the third layer, and effectively increase the energy gap to increase the long-wavelength spectrum utilization range to produce higher conversion efficiency. Wherein the grain size of the second layer of nanocrystalline semiconductor is 3ηϊη to 5nm', and the thickness of the third layer of nanocrystalline semiconductor is 5ηιη to i〇mn. The invention has the advantages that the thin film formed by the nanocrystalline semiconductor as the third layer of the light entrance layer can utilize the quantum confinement effect unique to the nanocrystalline crystal to enter the optical layer. The energy gap is increased, the open circuit voltage is increased, and the absorption range of the light is increased by the enhancement of the effective optical energy gap. For example, the light-input layer (p_layer) of the deposited solar cell enhances the utilization range of the short-wavelength spectrum, and the nanocrystalline crystal changes the material gap. Increase the range of long-wavelength spectrum utilization. Applying the size of the nanocrystalline structure 201251051 Controls the wavelength range of the absorbed spectrum, and its quantum "photon energy is approximately from L5eV to 2.GeV, and the absorbed energy is converted into a carrier'. Both ends of the positive and negative electrodes conduct the carriers out to form a current for light conversion. In addition, the present invention does not need to be a conventional heterojunction solar cell in which n_a_sic is required to incorporate carbon atoms or oxygen atoms in the deposition of a wide-gap film, and a narrow-energy gap film needs to be doped with germanium atoms; Technology: It can be formed to improve the current difficulties in developing multi-junction tandem solar cell process, effectively reducing the thickness of the ruthenium-based film in the thin film solar cell, shortening the process time and reducing the production cost. The embodiments and the technical description of the present invention are further described in the following examples, but it should be understood that the embodiments are merely illustrative and should not be construed as being The limit. 1 is a schematic view of an embodiment of a solar cell of the present invention. The upper layer is composed of a photoelectric conversion structure, the first layer is an n-type crystalline germanium semiconductor, and the first layer is a conductive type semiconductor layer, and the second layer is a crystalline amorphous semiconductor. The third layer is a p-type nanocrystalline semiconductor 30 having a conductivity type opposite to that of the first layer. A silver or metal layer is formed to form a back electrode 40 under the n-type crystalline germanium semiconductor 10. The transparent electrode 50 is a p-type nano-form formed by forming a germanium (indium tin oxide) or tin oxide electrode on the third layer. Above the spar semiconductor 30, and a layer of silver or aluminum metal forms a front electrode 6 on the surface of the transparent electrode 50. The method of manufacturing the solar cell of Fig. 1 described above is as follows. First, the n-type crystalline germanium semiconductor 10 having a thickness of 201251051 degrees and less than 400/zm is in a plasma-assisted chemical vapor deposition system (PECVD), SiH4 decane gas is introduced, the substrate is heated to about 120 ° C, and the plasma is turned on to make SiH4. The dissociation of the decane gas begins to deposit a hydrogen hydride film, such as decane, to form an intrinsic amorphous germanium semiconductor 20 of less than 5 nm on the surface of the intrinsic n-type crystalline germanium semiconductor 10. Then, on the surface of the intrinsic amorphous germanium semiconductor 20, a plasma-assisted chemical vapor deposition system (PECVD) is used to control parameters such as gas flow rate and plasma power to obtain a hydrogen-bonded nanoparticle (the crystal particle size can be Controlled in 1~30nm) crystalline dielectric film, which is a hydrogenated nanocrystalline nc-Si film, which is a third layer of P-type nanocrystalline semiconductor 30, thickness About 5nm to 1 Onm. Thereafter, the transparent electrode 50 is formed by vapor deposition or sputtering to form any known transparent conductive film (TCO) as a front electrode of a solar cell. Finally, the back electrode 40 is known by vapor deposition or similarly to the relationship between the energy gap value (Eg) and the grain size (L) from the back side of the n-type microcrystalline germanium semiconductor layer 10. When the grain size (L) of the third layer of the P-type nanocrystalline germanium semiconductor 30 is less than 5 nm, a quantum confinement effect will occur by the third layer of the P-type nanocrystalline semiconductor 30 material. The energy gap of the third layer of the amorphous germanium semiconductor layer material can be increased, forming a heterojunction with the intrinsic amorphous germanium semiconductor 20 of the second layer, and the open circuit voltage is increased to enable the third layer of material in the embodiment to be nanometerized. The gap is increased from 1.7 eV to 2.5 eV.
AE =\e28+ 2h2Eg(nlR)2 ImT 201251051 其中Δε為材料顆粒改變後之能隙；AE =\e28+ 2h2Eg(nlR)2 ImT 201251051 where Δε is the energy gap after the material particles are changed;
Eg為材料能隙； h為蒲朗克常數； R為材料顆粒大小； m*為材料等效質量。 所以’第三層的奈米晶矽半導體30能階式子為:Eg is the material energy gap; h is the Planck constant; R is the material particle size; m* is the material equivalent mass. So the third layer of nanocrystalline semiconductor 30 energy level is:
-EgikT-EgikT
Jo = J(m'Eg/kT 4.73*10— (T + 0.636) ΛJo = J(m'Eg/kT 4.73*10— (T + 0.636) Λ
Eg(T) = Eg(Q、-t 其中Jsc為短路電流密度，J0為逆向飽和電流。 藉由第三層p型奈米晶矽半導體30結構應用在太 陽能電池上做為入光層，可以有效的增加光波長範圍吸 收並增加太陽電池轉換的電能’提高整體的太陽能電池 效率’在精準控制第三層p型奈米晶矽半導體30的厚 度後’可使得產生的載子可以利用穿隧（Tunneling)效 應將載子傳送到兩端的電極40與電極60。 本說明實施例係以η型半導體作為第一層基板已被 描述在上述實施例中，很明顯的ρ型半導體基板也是可 以實施的。 惟以上所述者，僅為本發明之較佳實施例而已，當 不能以此限定本發明實施之範圍，即大凡依本發明申請 專利範圍及發明說明内容所作之簡單的等效變化與修 201251051 飾，皆仍屬本發明專利涵蓋之範圍内。 【圖式簡單說明】 圖1為本發明太陽能電池之實施.例示意圖。 圖2為能隙值(Eg)與晶粒大小(L)之關係圖。 【主要元件符號說明】 10 : η型結晶矽半導體 20 :本質非晶矽半導體 30 : ρ型奈米晶矽半導體 40 :背電極 50 :透明電極 60 :正面電極Eg(T) = Eg(Q, -t where Jsc is the short-circuit current density and J0 is the reverse saturation current. The third layer of p-type nanocrystalline germanium semiconductor 30 is applied to the solar cell as the light-in layer. Effectively increasing the wavelength range of light absorption and increasing the electrical energy converted by the solar cell 'Improving the overall solar cell efficiency' can accurately make the generated carriers use tunneling after precisely controlling the thickness of the third p-type nanocrystalline germanium semiconductor 30 The (Tunneling) effect transmits the carrier to the electrode 40 and the electrode 60 at both ends. The embodiment of the present invention uses an n-type semiconductor as the first layer substrate. In the above embodiment, it is apparent that the p-type semiconductor substrate can also be implemented. The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent change of the patent application scope and the description of the invention is修修201251051 Decorations are still covered by the patent of the present invention. [Simplified illustration of the drawings] Fig. 1 is a schematic view showing the implementation of the solar cell of the present invention. Fig. 2 is an energy gap value (Eg Relationship with grain size (L) [Description of main component symbols] 10 : η-type crystalline germanium semiconductor 20 : Intrinsic amorphous germanium semiconductor 30 : p-type nanocrystalline germanium semiconductor 40 : back electrode 50 : transparent electrode 60 : front electrode