JPH03285361A - Solar cell - Google Patents
Solar cellInfo
- Publication number
- JPH03285361A JPH03285361A JP2087192A JP8719290A JPH03285361A JP H03285361 A JPH03285361 A JP H03285361A JP 2087192 A JP2087192 A JP 2087192A JP 8719290 A JP8719290 A JP 8719290A JP H03285361 A JPH03285361 A JP H03285361A
- Authority
- JP
- Japan
- Prior art keywords
- region
- layer
- base
- emitter region
- impurity concentration
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 239000012535 impurity Substances 0.000 claims abstract description 34
- 239000004065 semiconductor Substances 0.000 claims abstract description 9
- 238000005215 recombination Methods 0.000 abstract description 6
- 230000006798 recombination Effects 0.000 abstract description 6
- 102100029391 Cardiotrophin-like cytokine factor 1 Human genes 0.000 abstract description 3
- 101000989964 Homo sapiens Cardiotrophin-like cytokine factor 1 Proteins 0.000 abstract description 3
- 230000002708 enhancing effect Effects 0.000 abstract 1
- 238000010248 power generation Methods 0.000 description 17
- 239000000969 carrier Substances 0.000 description 11
- 239000000758 substrate Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 230000008094 contradictory effect Effects 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
Classifications
-
- Y—GENERAL 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
Landscapes
- Photovoltaic Devices (AREA)
Abstract
Description
〈産業上の利用分野〉
本発明はベース領域の不純物濃度により影響を受ける性
能の改善を図った太陽電池に関する。
〈従来の技術〉
光起電力効果により光エネルギーを電気エネルギーに変
換する太陽電池は、クリーン且つ無尽蔵な発電システム
とし・てその利用が積極的に図られている。
第３図に従来の太陽電池の一例を示す。
この太陽電池は、Ｐ型半導体（Ｓｌ）基板の表面に高濃
度のＮ型拡散層を形成腰 Ｐ型のベース領域１を形成す
ると共にＮ３型のエミッタ領域２を形成しである。そし
て、基板の裏面には高濃度の不純物を拡散させてＰ゛型
のパックサーフエースフィールド’（ＢＳＦ）３が設け
られており、このＢＳＦ３の表面にはＡＩ等から成る電
極４が設けられている。また、基板の表面側には絶縁膜
（Ｓｉ０２）５を介してＡＩ等から成る電極６が設けら
れており、この電極６はエミッタ領域２に接続されてい
る。
この太陽電池によれは、表面側から光子エネルキーが禁
制帯幅より大きい光ｈνが照射されると、ＰＮ接合部の
光起電力効果で電極４．６間に電力が生ずる。そして、
この際、ＢＳＦ３はベース領域１の少数キャリア（この
場合、電子）をエミッ夕領域２側へ反射させて界面での
再結合を防止し、発電効率を向上させている。
〈発明が解決しようとする課題〉
従来より、太陽電池にはＢＳＦ３が設けられ、その発電
効率向上が図られているが、更なる効率向上が要望され
ている。
ここに、発電領域たるベース領域１の不純物濃度は発電
効率にとって重要である。すなわち、ベース領域の少数
キャリアの界面での再結合の減少、あるいは、ＰＮ接合
部の空乏層を広げて発生キャリアの収集効率の向上を図
り、これによって発電効率の向上を図るためには、ベー
ス領域１の不純物濃度は低い方がよい。一方、ベース領
域１からエミッタ領域２へ注入される少数キャリアぐ上
記例て：よ、電子）による暗電流成分の減少、あるいは
、電極間の直列抵抗の低減を図り、これによって発電効
率の向上を図るためには、・′＼−ス領域１の不純物濃
度は高い方がよい。
このようにベース＠域１の不純物濃度には相反する条件
があり、従来てはベース領域１の不純物濃度を両者の折
衷的な適当なものに設定していた。
しかしながら、大幅な発電効率の向上は実現できず、ま
た、微妙な濃度設定が必要なことから製造管理が煩雑と
なってし・まうという問題があった。
本発明は上記従来の事情に鑑みなされたもので、ベース
領域を不純物濃度の異なる多層構造とすることにより、
ベース領域に課せられる相反する条件を満足させ、発電
効率の大幅な向上を実現する太陽電池を提供することを
目的とする。
〈課題を解決するための手段〉
本発明に係る太陽電池は、−の導電型の半導体から成る
ベース領域に接して、他の導電型の半導体から成るエミ
ッタ領域を形成し・た太陽電池において、前記ベース領
域を不純物濃度の異なる複数層ここ形成し、前記エミッ
タ領域に接する・ベース層に較へて当該エミッタ領域か
ら遠い・ベース層の不純物濃度を高くしたことを特撮と
する。
〈作用〉
エミッタ領域に接するベース領域の不純物濃度を低くし
て、ベース領域の少数キャリアの界面での再結合を減少
させると共に、ＰＮ接合部の空乏層幅を広げる。そして
、エミッタ領域から遣いベース層の不純物濃度を高くし
て、ベース領域からエミッタ領域へ注入される少数キャ
リアによる暗電流成分を減少させると共に、電極間の直
列抵抗を低減させる。
〈実施例〉
本発明の太陽電池を実施例に基づいて具体的に説明する
。
第１図には本発明の一実施例に係る太陽電池を示す。尚
、前述し・た従来例と同一部分には同一符号を付して重
複する説明は省略する。
本実施例の太陽電池はＰ型半導体から成るベース領域を
不純物濃度の異なる２つの層１１ａ、１１ｂで形成して
あり、Ｎ型半導体から成るエミッタ領域２に接するベー
スＪｉ ］ ｌ ａの不純物濃度を低くしくＰ−）、エ
ミッタ領域２がら遠いベース層】】<Industrial Application Field> The present invention relates to a solar cell whose performance, which is affected by the impurity concentration in the base region, is improved. <Prior Art> Solar cells, which convert light energy into electrical energy through the photovoltaic effect, are actively being used as a clean and inexhaustible power generation system. FIG. 3 shows an example of a conventional solar cell. In this solar cell, a highly concentrated N-type diffusion layer is formed on the surface of a P-type semiconductor (Sl) substrate, a P-type base region 1 is formed, and an N3-type emitter region 2 is formed. Then, on the back surface of the substrate, a P' type Pack Surf Ace Field' (BSF) 3 is provided by diffusing impurities at a high concentration, and on the surface of this BSF 3, an electrode 4 made of AI or the like is provided. There is. Further, an electrode 6 made of AI or the like is provided on the surface side of the substrate via an insulating film (Si02) 5, and this electrode 6 is connected to the emitter region 2. In this solar cell, when light hv whose photon energy is larger than the forbidden band width is irradiated from the surface side, electric power is generated between the electrodes 4 and 6 due to the photovoltaic effect of the PN junction. and,
At this time, the BSF 3 reflects minority carriers (electrons in this case) in the base region 1 toward the emitter region 2 to prevent recombination at the interface, thereby improving power generation efficiency. <Problems to be Solved by the Invention> Conventionally, solar cells have been provided with BSF3, and attempts have been made to improve the power generation efficiency, but there is a demand for further efficiency improvement. Here, the impurity concentration of the base region 1, which is the power generation region, is important for power generation efficiency. In other words, in order to improve the collection efficiency of generated carriers by reducing the recombination of minority carriers in the base region at the interface or by expanding the depletion layer at the PN junction, and thereby improving the power generation efficiency, it is necessary to The lower the impurity concentration in region 1, the better. On the other hand, it is possible to reduce the dark current component due to minority carriers (for example, electrons) injected from the base region 1 to the emitter region 2, or to reduce the series resistance between the electrodes, thereby improving power generation efficiency. In order to achieve this, it is preferable that the impurity concentration of the .'\- space region 1 is high. As described above, there are contradictory conditions for the impurity concentration of the base@region 1, and conventionally, the impurity concentration of the base region 1 has been set to an appropriate value that is a compromise between the two. However, it has not been possible to achieve a significant improvement in power generation efficiency, and there has been a problem in that manufacturing management becomes complicated due to the need for delicate concentration settings. The present invention was made in view of the above-mentioned conventional circumstances, and by forming the base region into a multilayer structure with different impurity concentrations,
The objective is to provide a solar cell that satisfies the contradictory conditions imposed on the base region and achieves a significant improvement in power generation efficiency. <Means for Solving the Problems> A solar cell according to the present invention is a solar cell in which an emitter region made of a semiconductor of another conductivity type is formed in contact with a base region made of a semiconductor of a negative conductivity type. The base region is formed with a plurality of layers having different impurity concentrations, and the impurity concentration of the base layer which is in contact with the emitter region and which is further from the emitter region is higher than that of the base layer. <Operation> The impurity concentration of the base region in contact with the emitter region is lowered to reduce recombination of minority carriers in the base region at the interface and to widen the width of the depletion layer at the PN junction. Then, by increasing the impurity concentration in the base layer from the emitter region, the dark current component due to minority carriers injected from the base region to the emitter region is reduced, and the series resistance between the electrodes is reduced. <Example> The solar cell of the present invention will be specifically described based on an example. FIG. 1 shows a solar cell according to an embodiment of the present invention. Incidentally, the same parts as those in the conventional example described above are given the same reference numerals, and redundant explanation will be omitted. In the solar cell of this example, the base region made of a P-type semiconductor is formed of two layers 11a and 11b with different impurity concentrations, and the impurity concentration of the base Ji ] la in contact with the emitter region 2 made of an N-type semiconductor is Low P-), base layer far from emitter region 2]
【）の不純物濃度を
高くしである（Ｆｌ）。すなわち、エミッタ領域２は濃
度の低いベース層１１ａに形成され、このベース１ｌｌ
ａとＢＳＦ３との開にベースｆｉｌｌｂが介在する構造
となっている。但し、この・ベース層】１ｂの不純物濃
度は極端に高ぐするとキャリア〈この場合、電子）の拡
散長が短くなって発電領域としての機能が損なわれるの
で、この層１１ｂの不純物濃度はベース領域のキャリア
をエミッタ領域２側へ反射させる機能部分たるＥ（Ｓ
Ｆ ３の濃度〈Ｐ゛）より低く設定する。
上記のよう：こ互いに′ａ度の異なるベース領域１１ａ
、１ ｌ ｂを形成する方法としては、ベース層１１ｂ
の上：こ低濃度のベースＨ１１ａをエビタキシキ・ル戎
長させて形成する方法、低濃度（Ｐ−）の基板の裏面側
から不純物を拡散させて濃度の異なるベース層１１ａ、
１１ｂを形成する方法等かある。
上記構成の太陽電池によれは、不純物濃度の低＜ イベ
ース９Ｍ域１１ ａにより少数キャリアの界面での再結
合が減少すると共にＰ Ｎ接合部の空乏層幅が広がり、
不純物濃度の高いベース層１１ｂにより暗電流成分が減
少すると共に電極間の直列抵抗が低減し、総して発電効
率の向上が達成できる。
第３図に示した従来構造でベース領域１を厚さ５０μｍ
、不純物濃度Ｉ Ｘ １０ ”ｃｍ−３としたものに対
し、第１図に示した構造でベース層１１ａを厚さ１．０
μｍ、不純物濃度Ｉ Ｘ １０ ”’ａｍ−３ペース１
ｌｌｂを厚ざ４９ｔ１ｍ、不純物濃度５×１０１７ｃ！
ｍ″３としたものの発電効率を測定した。尚、両者共に
エミッタ領域２は厚さ０． ６μｎｌ、 不純物濃度
４Ｘ１０”ｃｍ−３８ＳＦ３は厚さ１．７μｍ、不純物
濃度５ Ｘ Ｉ ０１９ｃｍ−３とした。
この結果、第３図に示した従来構造のものｂ月５％であ
ったのに対し、第１図に示した構造のもの＃＜１９％で
あり、本発明を適用することにより発電効率が４％向上
した。
第２図には本発明の他の一実施例に係る太陽電池を示す
。
二の実施例において本発明を適用した太陽電池は、高濃
度Ｐ型コレクタ領域７をエミッタ領域２と同一面内に形
成して画電極４．６を基板の一面側に設定し、これら電
極の設けられた面とは反対側の面から光ｈνを照射する
ようにして光エネルギーの吸収効率を向上させたもので
ある。尚、図中の８．９は絶縁膜である。
この実施例の太陽電池にあってもエミッタ領域２とＢＳ
Ｆ３との間てベース領域を濃度の異なる２層１１ａ、ｌ
ｌｂから構成し、上記した実施例と同様に発電効率の向
上を図っている。
尚、上記した各実施例では、ベース領域を濃度の異なる
２層構造としたものを示したが、ベース領域を３層以上
の積層構造とし、これら各層の不純物濃度をエミッタ領
域から遠くなるに従って高くなるようにしてもよい。
また、上記した各実施例では、ベース領域のキャリアを
エミッタ領域側へ反射させるＢＳＦを備えたものを示し
たが、本発明はＢＳＦを（ｉｓえない太陽電池に適用し
ても所期の効果を得ることがてきる。
また、本発明では、導電型の■）Ｎ関係を上記実施例で
示したものとは逆にしてもよい。
く効果〉
本発明に係る太陽電池に３よれば、ベース領域を不純物
濃度の異なる複数層に形成し、エミッタ領域に接するベ
ース層に較べて当該エミッタ領域から遠い・ベース層の
不純物濃度を高くしたため、ベース領域の少数キャリア
の界面での再結合の減少及びＰＮＮ接合部空乏層幅の拡
大と、暗電流成分の減少及び電極間の直列抵抗の低減と
いう相反する要求を共に満足させることができ、総して
発電効率の大幅な向上が達成できる。
２はエミッタ領域、
３はバック（ノーフェースフィールド、４．６は電極、
５．８．９は絶縁層、
１１ａ、Ｉｌｂはベース層である。The impurity concentration of [) is increased (Fl). That is, the emitter region 2 is formed in the low concentration base layer 11a, and the emitter region 2 is formed in the base layer 11a with a low concentration.
The structure has a base fill b interposed between a and BSF3. However, if the impurity concentration of the base layer 1b is extremely high, the diffusion length of carriers (electrons in this case) will become short and the function as a power generation region will be impaired. E(S) is a functional part that reflects the carriers of
Set lower than the concentration of F3 (P゛). As above: base regions 11a with different degrees of 'a' from each other.
, 1 lb, the base layer 11b
Top: A method of forming a base layer 11a with a low concentration by elongating the base layer 11a, a base layer 11a with a different concentration by diffusing impurities from the back side of a low concentration (P-) substrate,
There are methods of forming 11b. The reason for the solar cell having the above structure is that due to the low impurity concentration, recombination of minority carriers at the interface is reduced and the width of the depletion layer at the PN junction is widened.
The base layer 11b with a high impurity concentration reduces the dark current component and reduces the series resistance between the electrodes, making it possible to improve the power generation efficiency as a whole. In the conventional structure shown in Figure 3, the base region 1 has a thickness of 50 μm.
, the impurity concentration is I x 10"cm-3, and the base layer 11a has a thickness of 1.0" in the structure shown in FIG.
μm, impurity concentration I x 10 ”'am-3 pace 1
llb has a thickness of 49t1m and an impurity concentration of 5x1017c!
The power generation efficiency was measured with the emitter region 2 having a thickness of 0.6 μnl in both cases, and the impurity concentration of 4×10”cm−38SF3 having a thickness of 1.7 μm and an impurity concentration of 5×I019cm−3. . As a result, the power generation efficiency of the conventional structure shown in Fig. 3 was 5%, while the power generation efficiency of the structure shown in Fig. 1 was <19%, and the power generation efficiency was improved by applying the present invention. It improved by 4%. FIG. 2 shows a solar cell according to another embodiment of the present invention. In the second embodiment, a solar cell to which the present invention is applied has a highly concentrated P-type collector region 7 formed in the same plane as the emitter region 2, and a picture electrode 4.6 set on one side of the substrate. The light energy absorption efficiency is improved by irradiating the light hv from the surface opposite to the surface on which it is provided. Note that 8.9 in the figure is an insulating film. Even in the solar cell of this example, the emitter region 2 and the BS
The base region is formed with two layers 11a and 11a with different concentrations between F3 and F3.
lb, and is intended to improve power generation efficiency in the same way as the above-mentioned embodiment. In each of the above embodiments, the base region has a two-layer structure with different concentrations, but the base region has a laminated structure of three or more layers, and the impurity concentration of each layer increases as the distance from the emitter region increases. You may do so. In addition, although each of the above-mentioned embodiments is equipped with a BSF that reflects carriers in the base region toward the emitter region, the present invention provides that even if the BSF is applied to a solar cell that does not have the desired effect. Further, in the present invention, the conductivity type ■)N relationship may be reversed from that shown in the above embodiment. Effect> According to 3 of the solar cell according to the present invention, the base region is formed into multiple layers with different impurity concentrations, and the impurity concentration of the base layer that is far from the emitter region is higher than that of the base layer that is in contact with the emitter region. , it is possible to satisfy the contradictory demands of reducing recombination of minority carriers in the base region at the interface and expanding the width of the PNN junction depletion layer, as well as reducing the dark current component and reducing the series resistance between the electrodes, Overall, a significant improvement in power generation efficiency can be achieved. 2 is an emitter region, 3 is a back (no face field), 4.6 is an electrode, 5.8.9 is an insulating layer, and 11a and Ilb are base layers.
Claims (1)
の導電型の半導体から成るエミッタ領域を形成した太陽
電池において、前記ベース領域を不純物濃度の異なる複
数層に形成し、前記エミッタ領域に接するベース層に較
べて当該エミッタ領域から遠いベース層の不純物濃度を
高くしたことを特徴とする太陽電池。In a solar cell in which an emitter region made of a semiconductor of another conductivity type is formed in contact with a base region made of a semiconductor of one conductivity type, the base region is formed in a plurality of layers with different impurity concentrations, and the base region is formed in contact with the emitter region. A solar cell characterized in that a base layer farther from the emitter region has a higher impurity concentration than the base layer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2087192A JPH03285361A (en) | 1990-03-31 | 1990-03-31 | Solar cell |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2087192A JPH03285361A (en) | 1990-03-31 | 1990-03-31 | Solar cell |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH03285361A true JPH03285361A (en) | 1991-12-16 |
Family
ID=13908125
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2087192A Pending JPH03285361A (en) | 1990-03-31 | 1990-03-31 | Solar cell |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH03285361A (en) |
-
1990
- 1990-03-31 JP JP2087192A patent/JPH03285361A/en active Pending
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