201218391 六、發明說明： 【發明所屬之技術領域】 本發明是有關於一種能增加光電流收集效率的太陽能電 池結構，尤指一種可有效保護太陽電池照光所產生之光電流， 使其遠離存在於窗口層表面的複合中心缺陷，以減少表面複合 效應(surface recombination)，而達到增加光電流收集效率之功 效者。 φ 【先前技術】 按’一般習用之太陽能電池3 (如第7圖所示），其包括 有基板31、背面電場層3 2、基極層3 3、射極層3 4、窗 口層3 5及接觸層3 6，其中該窗口層3 5可降低光電流在射 極層3 4表面附近的表面複合損失，進而提升載子效率。 而由該太陽能電池3照光而產生光電流之傳遞與收集路 徑可知，即便有窗口層3 5可α降低光電流在射極層3 4表面 之複合效應，但仍然無法避免光電流在窗口層3 5表面發生表 • 面複合效應’此現象尤其在聚光條件下更為顯著；以該電流路 徑來說明，該路徑a具有最低的表面複合效應，因此，收集效 率最佳，路往c則具有最高的表面複合效應，因此，收集效率 最差；而路徑b則是介於兩者之間，由於路徑e是太陽電池最 主要的光電流產生區域，因此，如何降低路徑c之表面複合效 應，進而提升載子收集效率，是聚光型太陽電池之一重要核心 議題。 目刖文獻上有報導利用表面硫化處理，來降低窗口層上表 面之複合效應’進而提高載子收集效率。硫化溶液有多種不同 201218391 型式，包括N^S、（NH^S、與(NH^Sx等等。文獻報導，以 (NH^Sx溶液進行硫化’效果較佳。其原理說明如下：以窗口 層材質是AllnP為例子，未施以硫化處理之前，窗口層上表面 存在許多與氧相關的鍵結，包括!鍵結與AJ—0鍵結，這些 鍵結皆屬再結合中心(recombination centers)，這些表面離 (surfacestates)容易捕捉光電流，增加表面複合速率。若施以硫 化處理’則這些與氧相關的鍵結會被硫原子取代而形成hs鍵 結與A1-S鍵結，因而降低表面態密度，降低表面複合速率； 但窗口層之表面硫化處理至少會產生有下列之缺點： 1 · (NH^Sx溶液對太陽電池其他膜層結構是否會衍生其他 副化學反應，目前文獻上仍未有詳盡報導。 2 ·對於須在聚光條件下操作的太陽能電池而言，結構之耐 高溫特性是重要考量。一旦窗口層表面之氧相關鍵結被硫原子 取代而形成硫原子相關鍵結，其對溫度的穩定性目前文獻上仍 未有詳盡報導。 然’除了上述之表面硫化處理方法之外，目前更有相關專 利利用改善窗口層本身材質來降低表面複合，材質選擇包括晶 格匹配類型與晶格不匹配類型。此外亦有報導利用氧化膜層來， 減少懸浮鍵結(dangling bond丨。 例如下列相關之美國專利與中華民國專利： 1·美國專利第 4,276，137 號之「Control 〇f surface recombination loss in solar cells j» 2. 美國專利第 7,119,271 號之「lattice-mismatchedwindow layer for a solar conversion device」。 3. 美國專利第 7,763,917 號之「Photovoltaic devices with [s] 4 201218391 silicon dioxide encapsulation layer and method to make samej e 4. 美國專利第 4,935,384 號之「Method of passivating semiconductor surfaces」〇 5. 中華民國專利公開第200901493號「製造太陽能電池 可用之氮化梦鈍化層的方法」。 6. 中華民國專利公開第200814344號之「具有減小之基 極擴散區域的太陽能電池」。 • 7.中華民國專利公開第200841478號之「矽晶太陽電池 與矽晶太陽電池之背電極的製造方法」。 而就上述各專利而言，無論是選擇晶格匹配類型或晶格不 匹配類型的窗口層材質，或是利用氧化膜層對窗口層的表面鈍 化覆蓋方式，窗口層表層必定仍存在氧相關缺陷，會減少光電 流的收集效率。 【發明内容】 籲本發明之主要目的係在於，可使表面能障層與窗口層之界 面處形成之内建電場，以有效保護太陽電池照光所產生之光電 流，使其遠離存在於窗口層表面的複合中心缺陷，以減少表面 複合效應，而達到增加光電流收集效率之功效。 為達上述之目的，本發明係一種能增加光電流收集效率的 太陽能電池結構，包含端面設有窗口層之太陽能電池；以及一 覆蓋於窗口層表面上之表面能障層，該表面能障層係可為磷化 物或神化物。 於本發明之一實施例中，該太陽能電池至少包含有一基 201218391 板、一層疊於基板上之緩衝層、一層疊於緩衝層上之背面電場 層、一層疊於背面電場層上之基極層、及一層疊於基極層上之 射極層、而該窗口層係層疊於射極層上’且於該窗口層上係設 有—接觸層’而形成一單接面太陽能電池。 於本發明之一實施例中，該太陽能電池至少包含有一基 板、一層疊於基板上之緩衝層、一層疊於緩衝層上之第一背面 電場層、—層4於第-背面電場層上n極層、一層叠於 第一基極層上之第一射極層、一層疊於第一射極層上之第一窗 口，、-層Φ於第H上之第二背面電場層、—層叠於第 二背面電場層上之第二基極層、—層疊於第二基極層上之第二 射極層…層Φ於第二射極層上之第二窗σ層及—層叠於第 二窗口層上之接觸層，而形成一雙接面太陽能電池，且使該表 面能障層覆蓋第二窗口層之表面上β β 於本發明之—實施射，該太陽能電池至少包含有一基 板、-層4於基板上之成核層、—層疊於成核層上之第一背面 電場層、-層疊於第—背面電場層上之第-基極層、一層叠於 第-基極層上之第-射極層、—層疊於第—射極層上之第一窗 :層、-層4於第-窗口層上之第二背面電場層、—層疊於第 #面電场層上之第二基極層、一層曼於第二基極層上之第二 射極層、—層4於第二射極層上之第二窗口層、及—層叠於第 -窗口層上之接觸層’而形成三接面太陽能電池且使該表面 能障層覆蓋於第二窗口層之表面上。 於本發明之—實施财，該窗口祕可為ρ型AlGaAs， :該表面能障層係可為相反極性之n型_々Λ5ΐ〇〇5ρ 中該χ=0〜1。 6 201218391 於本發明之一實施例中，該窗口層係可為p型WGAs , 而該表面能障層係可為相同極性之p型(AlyGai y)〇5ln〇5P，且其 中該0〜1。 於本發明之一實施例中，該窗口層係可為P型 (AlxGa^VsIn^p，而該表面能障層係可為相反極性之η型 AlyGa^yAs ,而其令該 y= 。 於本發明之一實施例中，該窗口層係可為ρ型 (A^Ga^Jo·5!^sp，而該表面能障層係可為相同極性之ρ型 AlzGakAs，而其中該 2=0^1。 於本發明之一實施例中，該表面能障層至少係以塗佈光 阻、軟烤、曝光、硬烤、顯影、表面能障層之局部蝕刻及移除 光’阻之步驟成型覆蓋於窗口層之表面上。 • . 【實施方式】 請參閱『第1、2、3及第4圖j所示，係分別為本發明 第一實施例之示意圖、本發明表面能障層之成型示意圖、本發 明接觸層之成型示意圖及本發明第一實施例之使用权態示意 圖。如圖所示：本發明係一種能增加先電流收集效率的太陽能 電池結構’其至少包含有_太陽能電池丨以及_表面能障層2 所構成。 一太陽能電池1至少包含有一基板10、一層疊於基板1 0上之緩衝層11、一層疊於緩衝層1 1上之背面電場層1 2、一層疊於背面電場層12上之基極層13、及一層疊於基 極層13上之射極層14、一層疊於射極層14上之窗口層1 5、及一層疊於窗口層15上之接觸層16，而形成一單面 201218391 太陽能電池。 該表面能障層2係覆蓋於窗口層15之表面上，而該表面 能障層2係可為磷化物或砷化物。 當本發明於製作時，係將該表面能障層2以塗佈光阻、軟 烤、曝光、硬烤、顯影、表面能障層2之局部蝕刻及移除光阻 等黃光製程步驟成型覆蓋於窗口層15之表面上（如第2圖所 示）’之後再利用金屬有機化學氣相沈積(MOCVD)於窗口層i 5之適當處進行再生層（regrowth)，而成長一層重摻雜之p型 GaAs接觸層16 (如第3圖所示），最後再施以標準的太陽電 池製作流程即可獲得具有表面能障層2之太陽能電池1 (如第 1圖所示）。 由於本實施例之基板1 〇係可為η型GaAs基板，而該窗 口層1 5之材料係為p型AlGaAs，因此，一旦成長完窗口屠 1 5之後，隨即成長一層採用n型AllnP表面能障層2，藉以 可有效減少窗口層15表面複合效應，以提昇載子收集效率， 進而提高太陽電池轉換效率β 另外該表面能障層2之材質選擇視下層窗口層15之材料 而定’例如該窗口層1 5係為ρ型AlGaAs，則表面能障層2 的材質可以是極性相反之η型(AlxGal-x)0.5In0.5P ,其中 x=(M、或是極性相同之ρ型(AlyGal-y)0.5In0.5P ,其中产 (M ;又例如該窗口層1 5係為ρ型(AlxGal-x)0.5In0.5P ’則表 面能障層2之材質可以是極性相反之η型AlyGal-yAs，其中 0~1、或是極性相同之p型AlzGal-zAs，其中z= 0〜1 〇當然， 對於其他晶格不匹配體系(metamoiphic)之太陽能電池而言，其 窗口層材質可能不是AlGaAs、（AlxGal-x)0.5In0.5P，因此，其 8 201218391 對應之表面能障層材質選擇亦可能隨之而變。 而當使用時（如第4圖所示），無論是選用極性相反之n 型AlGalnP，或是極性相同之ρ型所形成之表面能障 層2材料，皆會在該表面能障層2與窗口層15之界面處形成 一内建電場A，而此内建電場A能有效推離光電流聚集在窗口 層15表面’並進而大幅降低光電流在窗口層15表面之複合 效應’而提高太陽能電池1之轉換效率。 請參閱Γ第5圖j所示’係本發明第二實施例之剖面狀態 示意圖。如厨所示： 該太陽能電池1 a亦可包含有一基板1〇 a、一層疊於基 板10 a上之緩衝層11 a、一層疊於緩衝層11a上之第一 背面電場層12 a、一層疊於第一背面電場層12 a上之第一 基極層13 a、一層疊於第一基極層13 3上之第一射極層1 4 a、一層疊於第一射極層14 a上之第一窗口層15 a、一 層疊於第一窗口層15 a上之第二背面電場層16 a、一層疊 於第二背面電場層15 a上之第二基極層17 a、一層疊於第 二基極層1 7 a上之第二射極層1 8 a、一層疊於第二射極層 18 a上之第二窗口層19 a、及一層疊於第二窗口層19 a 上之接觸層191 a ’藉以形成一雙接面太陽能電池，且使該 表面能障層2以第一實施例之方式覆蓋於第二窗口層19 a 之表面上；如此，除可同樣達到上述第一實施例所提供效之 外，更能符合實際使用時之所需。201218391 VI. Description of the Invention: [Technical Field] The present invention relates to a solar cell structure capable of increasing photocurrent collection efficiency, and more particularly to a photocurrent that can effectively protect solar cell illumination from being present Composite center defects on the surface of the window layer to reduce surface recombination, and to achieve the effect of increasing the efficiency of photocurrent collection. φ [Prior Art] According to the 'usually used solar cell 3 (as shown in Fig. 7), it includes a substrate 31, a back surface electric field layer 3, a base layer 33, an emitter layer 34, and a window layer 3 5 And the contact layer 3 6, wherein the window layer 35 can reduce the surface recombination loss of the photocurrent near the surface of the emitter layer 34, thereby improving the efficiency of the carrier. The light source current transmission and collection path is illuminated by the solar cell 3, and even if the window layer 35 can reduce the composite effect of the photocurrent on the surface of the emitter layer 34, the photocurrent cannot be avoided in the window layer 3. 5 Surface occurrence surface • Surface composite effect' This phenomenon is more pronounced especially in concentrating conditions; this current path indicates that the path a has the lowest surface recombination effect, so the collection efficiency is the best, and the path to c has The highest surface recombination effect, therefore, the collection efficiency is the worst; and the path b is between the two, since the path e is the most important photocurrent generation region of the solar cell, therefore, how to reduce the surface recombination effect of the path c, Further improving the efficiency of carrier collection is an important core issue for concentrating solar cells. It has been reported in the literature that surface vulcanization treatment is used to reduce the composite effect of the surface on the window layer, thereby improving the efficiency of carrier collection. There are many different types of vulcanization solutions in 201218391, including N^S, (NH^S, and (NH^Sx, etc.). The literature reports that the effect of vulcanization with NH^Sx solution is better. The principle is as follows: The material is AllnP as an example. Before the vulcanization treatment, there are many oxygen-related bonds on the upper surface of the window layer, including the ! bond and the AJ-0 bond. These bonds are recombination centers. These surface states are easy to capture photocurrents and increase the surface recombination rate. If vulcanization is applied, these oxygen-related bonds are replaced by sulfur atoms to form hs bonds and A1-S bonds, thus reducing the surface. The density of states reduces the surface recombination rate; however, the surface vulcanization treatment of the window layer has at least the following disadvantages: 1 · (NH^Sx solution will derivate other sub-chemical reactions on other film structures of solar cells, which is still not in the literature. There are detailed reports. 2 · For solar cells that must be operated under concentrating conditions, the high temperature resistance of the structure is an important consideration. Once the oxygen-related bond on the surface of the window layer is taken by the sulfur atom The formation of sulfur atom-related bonds, its temperature stability has not been reported in detail in the literature. However, in addition to the above surface vulcanization treatment methods, there are more related patents to improve the surface layer composite by improving the material of the window layer itself. The material selection includes the lattice matching type and the lattice mismatch type. In addition, it has been reported to use the oxide film layer to reduce the dangling bond. For example, the following related US patents and Republic of China patents: 1. US Patent No. No. 4,276,137, "Control 〇f surface recombination loss in solar cells j» 2. "lattice-mismatched window layer for a solar conversion device", US Patent No. 7,119,271. 3. Photovoltaic devices with [US Patent No. 7,763,917] s] 4 201218391 silicon dioxide encapsulation layer and method to make samej e 4. US Patent No. 4,935,384 "Method of passivating semiconductor surfaces" 〇 5. Republic of China Patent Publication No. 200901493 "Manufacturing nitride passivation layer for solar cells Method. 6. Chinese people Patent Publication No. 200814344 of the "having a reduced base diffusion region of a solar cell." • 7. The method of manufacturing the back electrode of a twinned solar cell and a twinned solar cell of the Republic of China Patent Publication No. 200841478. As far as the above patents are concerned, whether the window layer material of the lattice matching type or the lattice mismatch type is selected, or the surface passivation covering method of the window layer by the oxide film layer is used, the oxygen layer-related defects are still present in the surface layer of the window layer. Will reduce the collection efficiency of photocurrent. SUMMARY OF THE INVENTION The main object of the present invention is to create a built-in electric field at the interface between the surface energy barrier layer and the window layer to effectively protect the photocurrent generated by the solar cell illumination from being present in the window layer. The composite center defect of the surface reduces the surface recombination effect and achieves the effect of increasing the efficiency of photocurrent collection. In order to achieve the above object, the present invention is a solar cell structure capable of increasing photocurrent collecting efficiency, comprising a solar cell having a window layer on an end surface thereof; and a surface energy barrier layer covering the surface of the window layer, the surface energy barrier layer The system can be a phosphide or a derivative. In an embodiment of the invention, the solar cell comprises at least a base 201218391 plate, a buffer layer laminated on the substrate, a back electric field layer laminated on the buffer layer, and a base layer laminated on the back electric field layer. And an emitter layer stacked on the base layer, wherein the window layer is laminated on the emitter layer and a contact layer is formed on the window layer to form a single junction solar cell. In an embodiment of the invention, the solar cell comprises at least a substrate, a buffer layer laminated on the substrate, a first back surface electric field layer laminated on the buffer layer, and a layer 4 on the first-back surface electric field layer. a pole layer, a first emitter layer stacked on the first base layer, a first window laminated on the first emitter layer, a second back surface electric field layer on the Hth layer, and a layer a second base layer on the second back surface field layer, a second emitter layer layered on the second base layer, a second window σ layer on the second emitter layer, and a layer Forming a contact layer on the second window layer to form a double junction solar cell, and causing the surface energy barrier layer to cover β β on the surface of the second window layer for performing the invention, the solar cell comprising at least one substrate, a nucleation layer on the substrate 4, a first back surface electric field layer laminated on the nucleation layer, a first base layer laminated on the first back surface electric field layer, and a layer stacked on the first base layer a first-emitter layer, a first window laminated on the first emitter layer: a layer, and a layer 4 on the first window layer a back surface electric field layer, a second base layer stacked on the ## surface electric field layer, a second emitter layer on the second base layer, and a layer 4 on the second emitter layer A two-window layer, and a contact layer laminated on the first-window layer, form a three-junction solar cell and the surface barrier layer covers the surface of the second window layer. In the present invention, the window may be p-type AlGaAs, and the surface energy barrier layer may be n-type _々Λ5ΐ〇〇5ρ of opposite polarity. 6 201218391 In an embodiment of the present invention, the window layer may be p-type WGAs, and the surface energy barrier layer may be p-type (AlyGai y) 〇 5ln〇5P of the same polarity, and wherein the 0~1 . In an embodiment of the invention, the window layer may be P-type (AlxGa^VsIn^p, and the surface energy barrier layer may be n-type AlyGa^yAs of opposite polarity, and let the y=. In an embodiment of the present invention, the window layer may be a p-type (A^Ga^Jo·5!^sp, and the surface energy barrier layer may be a p-type AlzGakAs of the same polarity, wherein the 2=0 In one embodiment of the present invention, the surface energy barrier layer is at least coated with photoresist, soft baked, exposed, hard baked, developed, partially etched with a surface energy barrier, and removed from the light barrier. The molding is applied to the surface of the window layer. [Embodiment] Please refer to "1, 2, 3, and 4, which are schematic views of the first embodiment of the present invention, and the surface energy barrier layer of the present invention. FIG. 2 is a schematic view showing the molding of the contact layer of the present invention and a schematic diagram of the use of the first embodiment of the present invention. As shown in the figure, the present invention is a solar cell structure capable of increasing the efficiency of current collection, which includes at least solar energy. The battery pack and the surface energy barrier layer 2 are formed. A solar cell 1 includes at least one substrate 1 0, a buffer layer 11 laminated on the substrate 10, a back surface electric field layer 12 laminated on the buffer layer 11, a base layer 13 laminated on the back surface electric field layer 12, and a layer stacked on the base layer The emitter layer 14 on the 13th, the window layer 15 stacked on the emitter layer 14, and the contact layer 16 laminated on the window layer 15 form a single-sided 201218391 solar cell. The surface barrier layer 2 can be phosphide or arsenide. When the invention is fabricated, the surface barrier layer 2 is coated with photoresist, soft baked, The yellow light process steps of exposure, hard baking, development, partial etching of the surface energy barrier 2, and removal of photoresist are formed on the surface of the window layer 15 (as shown in FIG. 2), and then the metal organic chemical gas is used. Phase deposition (MOCVD) performs a regrowth at the appropriate portion of the window layer i 5, and a heavily doped p-type GaAs contact layer 16 (as shown in FIG. 3) is grown, and finally a standard solar cell is applied. The solar cell 1 having the surface barrier layer 2 can be obtained by the production process (as shown in Fig. 1). The substrate 1 of the embodiment may be an n-type GaAs substrate, and the material of the window layer 15 is p-type AlGaAs. Therefore, once the window is grown, a layer of n-type AllnP surface barrier layer is grown. 2, thereby effectively reducing the surface recombination effect of the window layer 15 to improve the carrier collection efficiency, thereby improving the solar cell conversion efficiency β, and the material selection of the surface energy barrier layer 2 depends on the material of the lower window layer 15 'for example, the window The layer 1 5 is p-type AlGaAs, and the surface barrier layer 2 may be made of the opposite polarity n-type (AlxGal-x) 0.5In0.5P, where x=(M, or the same polarity of the p-type (AlyGal- y) 0.5In0.5P, wherein (M; for example, the window layer 15 is p-type (AlxGal-x) 0.5In0.5P ', then the material of the surface barrier layer 2 may be the opposite polarity η-type AlyGal- yAs, where 0~1, or p-type AlzGal-zAs of the same polarity, where z=0~1 〇 Of course, for other lattice-mismatched (metamoiphic) solar cells, the window layer material may not be AlGaAs , (AlxGal-x) 0.5In0.5P, therefore, its 8 201218391 corresponding surface energy barrier material selection It may change accordingly. When used (as shown in Fig. 4), either the n-type AlGalnP of opposite polarity or the surface energy barrier 2 formed by the p-type of the same polarity will be in the surface barrier layer 2 A built-in electric field A is formed at the interface of the window layer 15, and the built-in electric field A can effectively push away the photocurrent from the surface of the window layer 15 and further reduce the composite effect of the photocurrent on the surface of the window layer 15 to improve solar energy. Conversion efficiency of battery 1. Referring to Figure 5, a schematic cross-sectional view of a second embodiment of the present invention is shown. As shown in the kitchen: the solar cell 1a may further include a substrate 1A, a buffer layer 11a laminated on the substrate 10a, a first back surface electric field layer 12a laminated on the buffer layer 11a, and a stack a first base layer 13a on the first back surface field layer 12a, a first emitter layer 14a stacked on the first base layer 133, and a layer on the first emitter layer 14a a first window layer 15a, a second back surface layer 16a laminated on the first window layer 15a, and a second base layer 17a laminated on the second back surface layer 15a. a second emitter layer 18a on the second base layer 17a, a second window layer 19a stacked on the second emitter layer 18a, and a layer stacked on the second window layer 19a The contact layer 191a' is formed to form a double junction solar cell, and the surface barrier layer 2 is covered on the surface of the second window layer 19a in the manner of the first embodiment; In addition to the effects provided by the embodiments, it is more suitable for the actual use.
SISI
請參閱『第6圖』所示，係本發明第三實施例之剖面狀態 示意圖。如圖所示：該太陽能電池1b亦可包含有一基板1〇 b、一層疊於基板1〇 b上之成核層1〇1b、一層疊於成核I 9 201218391 層101b上之第一背面電場層丄2 b、一層疊於第一背面電 場層12 b上之第一基極層13 b、一層疊於第一基極層工3 b上之第一射極層χ 4 b、一層疊於第一射極層丄4 b上之第 -窗口層15b、-層疊於第一窗口層工5b上之第二背面電 場層16b、-層疊於第二背面電場層16b上之第二基極層 17b、一層疊於第二基極層丄7b上之第二射極層i8b、 一層疊於第二射極層18b上之第二窗口層1gb、及一層疊 於第二窗口層19b上之接觸層19!b，藉以形成三接面太 鲁 陽能電池，且使該表面能障層2以第一實施例之方式覆蓋於第 二窗口層19 b之表面上；如此，除可同樣達到上述第一實施 例所提供效之外’更能符合實際使用時之所需。 综上所述，本發明能增加光電流收集效率的太陽能電池結 構可有效改善習用之種種缺點，可使表面能障層與窗口層之界 面處形成之内建電場，以有效保護太陽電池照光所產生之光電 流’使其遠離存在於窗口層表面的複合中心缺陷，以減少表面 複合效應(surface recombination)，而達到增加光電流收集效率 鲁 之功效；進而使本發明之産生能更進步、更實用、更符合消費 者使用之所須，確已符合發明專利申請之要件，爰依法提出專 利申請。 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；故，凡依本發明申請專利範圍及發 明說明書内容所作之簡單的等效變化與修飾，皆應仍屬本發明 專利涵蓋之範圍内。 【圖式簡單說明】 201218391 第1圖，係本發明第一實施例之示意圖。 第2圖，係本發明表面能障層之成型示意圖。 第3圖，係本發明接觸層之成型示意圖。 第4圖，係本發明第一實施例之使用狀態示意圖。 第5圖，係本發明第二實施例之剖面狀態示意圖。 第6圖，係本發明第三實施例之剖面狀態示意圖。 第7圖，係習用太陽能電之示意圖。 【主要元件符號說明】 (本發明部分） 太陽能電池1、1 a、1b 基板10、10a、l〇b 成核層10 lb 緩衝層11、11 a 背面電場層12 第一背面電場層12 a 第一背面電場層12b 基極層1 3 第一基極層13 a、13 b 射極層1 4 第一射極層14 a、14b 窗口層1 5 第一窗口層15 a、15b 接觸層1 6 第二背面電場層16 a、16 b [si 11 201218391 第二基極層17a、17b 第二射極層18 a、18b 第二窗口層19 a、19 b 接觸層191a、191b 表面能障層2 内建電場A (習用部分） 太陽能電池3 基板3 1 背面電場層32 基極層3 3 射極層3 4 窗口層3 5 接觸層3 6 路徑a 路徑b 路徑c 12Referring to Fig. 6, there is shown a schematic cross-sectional view of a third embodiment of the present invention. As shown in the figure, the solar cell 1b may further include a substrate 1〇b, a nucleation layer 1〇1b laminated on the substrate 1〇b, and a first back surface electric field laminated on the nucleation I 9 201218391 layer 101b. a layer 2b, a first base layer 13b laminated on the first back surface layer 12b, and a first emitter layer χ4b laminated on the first base layer 3b, stacked on a first window layer 15b on the first emitter layer b4b, a second back surface electric field layer 16b laminated on the first window layer 5b, and a second base layer laminated on the second back surface field layer 16b 17b, a second emitter layer i8b laminated on the second base layer b7b, a second window layer 1gb laminated on the second emitter layer 18b, and a contact laminated on the second window layer 19b a layer 19!b, thereby forming a three-junction solar cell, and covering the surface barrier layer 2 on the surface of the second window layer 19b in the manner of the first embodiment; In addition to the effects provided by the first embodiment, it is more suitable for the actual use. In summary, the solar cell structure capable of increasing the photocurrent collecting efficiency of the present invention can effectively improve various disadvantages of the conventional use, and can form an internal electric field formed at the interface between the surface energy barrier layer and the window layer to effectively protect the solar cell illumination. The generated photocurrent 'removes away from the composite center defect existing on the surface of the window layer to reduce the surface recombination, thereby achieving the effect of increasing the photocurrent collection efficiency; thereby making the invention more progressive and more Practical and more in line with the needs of consumers, it has indeed met the requirements of the invention patent application, and filed a patent application according to law. However, the above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto; therefore, the simple equivalent changes and modifications made in accordance with the scope of the present invention and the contents of the invention are modified. All should remain within the scope of the invention patent. BRIEF DESCRIPTION OF THE DRAWINGS 201218391 Fig. 1 is a schematic view showing a first embodiment of the present invention. Fig. 2 is a schematic view showing the formation of the surface energy barrier layer of the present invention. Figure 3 is a schematic view showing the formation of the contact layer of the present invention. Fig. 4 is a view showing the state of use of the first embodiment of the present invention. Fig. 5 is a schematic cross-sectional view showing a second embodiment of the present invention. Figure 6 is a schematic cross-sectional view showing a third embodiment of the present invention. Figure 7 is a schematic diagram of conventional solar power. [Description of main component symbols] (part of the invention) solar cell 1, 1 a, 1b substrate 10, 10a, lb nucleation layer 10 lb buffer layer 11, 11 a back surface electric field layer 12 first back surface electric field layer 12 a a back surface field layer 12b a base layer 13 a first base layer 13 a, 13 b an emitter layer 14 a first emitter layer 14 a, 14b a window layer 1 5 a first window layer 15 a, 15b a contact layer 1 6 Second back surface electric field layer 16 a, 16 b [si 11 201218391 second base layer 17a, 17b second emitter layer 18 a, 18b second window layer 19 a, 19 b contact layer 191a, 191b surface energy barrier layer 2 Built-in electric field A (conventional part) Solar cell 3 Substrate 3 1 Back side electric field layer 32 Base layer 3 3 Emitter layer 3 4 Window layer 3 5 Contact layer 3 6 Path a Path b Path c 12