JP2004296712A

JP2004296712A - Photoelectric converter and method for manufacturing the same

Info

Publication number: JP2004296712A
Application number: JP2003086063A
Authority: JP
Inventors: Youji Seki; 洋二積; Yoshio Miura; 好雄三浦; Makoto Sugawara; 信菅原; Hisao Arimune; 久雄有宗
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2003-03-26
Filing date: 2003-03-26
Publication date: 2004-10-21
Anticipated expiration: 2023-03-26
Also published as: JP4153814B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive and reliable photoelectric converter. <P>SOLUTION: As for the photoelectric converter, a large number of granular crystal semiconductors 2 showing a single conduction type are disposed on a substrate 1 being an electrode of one side, an insulator 3 is interposed among the semiconductors 2, semiconductor layers 4 showing an inverse conduction type are formed on the semiconductors 2, and a conduction layer 5 being the other electrode is formed on the semiconductor layers 4 showing the inverse conduction type. Since the insulator 3 consists of polyimide curing at ≤250°C and is interposed between the semiconductor layers 4 and the conduction layer 5 at the lower part of the granular crystal semiconductors, a clean and large PN connection surface is secured and the insulator 3 is formed without thermally damaging PN connection. Thus, compared with a conventional photoelectric converter, the photoelectric converter with high conversion performance is manufactured inexpensively and easily, thereby providing the reliable photoelectric converter. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は太陽光発電などに使用される光電変換装置とその製造方法に関し、特に粒状結晶半導体を用いた光電変換装置とその製造方法に関する。
【０００２】
【従来の技術】
従来の粒状結晶半導体を用いた光電変換装置を図３〜図６に示す。例えば図３に示すように、第１のアルミニウム箔９に開口を形成し、その開口にｐ型の上にｎ型表皮部８を持つシリコン球２を挿着し、このシリコン球２の裏側のｎ型表皮部８を除去し、第１のアルミニウム箔９の裏面側に酸化物絶縁層３を形成し、シリコン球２の裏側の酸化物絶縁層３を除去し、シリコン球２と第２のアルミニウム箔７とを接合する光電変換装置が開示されている（例えば特許文献１参照）。
【０００３】
また、図４に示すように、基板１上に低融点金属層１０を形成し、この低融点金属層１０上に第１導電型の粒状結晶半導体２を配設し、この粒状結晶半導体２上に第２導電型のアモルファス半導体層６を上記低融点金属層１０との間に絶縁層３を介して形成する光電変換装置が開示されている（例えば特許文献２参照）。
【０００４】
また、図５に示すように、基板１上に高融点金属層１１と低融点金属層１０と半導体微小結晶粒１２とを堆積し、半導体微小結晶粒１２を融解させて飽和させた上で徐々に冷却して半導体を液相エビタキシャル成長させることによって多結晶薄膜１２を形成する方法が開示されている（例えば特許文献３参照）。
【０００５】
また、図６に示すように、シート状のモジュール基板１上に複数の第１導電型の球状半導体１６を導電ぺースト１４によって接着された状態で熱可塑性透明柔軟樹脂１７中に埋設し、球状半導体１６の表面領域に不純物を熱拡散あるいはイオン注入によってドープすることで第２導電型の表面層４を形成する方法が開示されている（例えば特許文献４参照）。
【０００６】
なお、図４、図５、図６において、５は透明導電膜などから成る電極である。
【０００７】
【特許文献１】
特開昭６１−１２４１７９号公報
【特許文献２】
特許第２６４１８００号公報
【特許文献３】
特公平８−３４１７７号公報
【特許文献４】
特開２００１−２３０４２９号公報
【０００８】
【発明が解決しようとする課題】
しかしながら、図３に示すような光電変換装置では、第１のアルミニウム箔９に開口を形成し、その開口にシリコン球２を押し込んでシリコン球２を第１のアルミニウム箔９に接合させる必要があるため、シリコン球２の球径に均一性が要求され、高コストになるという問題があった。また、接合させるときの処理温度がアルミニウムとシリコンとの共晶温度である５７７℃以下であるため、接合が不安定になるという問題があった。
【０００９】
また、図４に示すような光電変換装置によれば、第１導電型の粒状結晶半導体２上に第２導電型のアモルファス半導体層６を設けるため、安定なｐｎ接合を形成するにはアモルファス半導体層６を形成する前に粒状結晶半導体２の表面を十分にエッチングおよび洗浄する必要があった。また、アモルファス半導体層６の光吸収が大きいことに起因して膜厚を薄くしなければならず、アモルファス半導体層６の膜厚が薄い場合、欠陥に対する許容度も小さくなり、洗浄工程や製造環境の管理を厳しくする必要があり、その結果、高コストになるという問題があった。
【００１０】
また、図５に示すような光電変換装置によれば、低融点金属層１０が第１導電型の液相エピタキシャル多結晶層１２中に混入するために性能が落ち、また絶縁体がないために上部電極５と下部電極１１との間にリークが発生するという問題があった。
【００１１】
また、図６に示すような光電変換装置によれば、第１導電型の球状半導体１６の導電性ペースト１４との接合部には高濃度層が存在しないため、光子により励起された電子の障壁、いわゆるバックフィールド効果を得ることができず、光電変換効率が低下することが判明した。
【００１２】
本発明は上記従来技術の問題点に鑑みてなされたものであり、その目的は、低コストで高性能な信頼性の高い光電変換装置とその製造方法を提供することにある。
【００１３】
【課題を解決するための手段】
上記目的を達成するために、請求項１に係る光電変換装置は、一方の電極となる基板上に一導電型を呈する粒状結晶半導体を多数配設し、この粒状結晶半導体間に絶縁体を介在させ、この粒状結晶半導体上に逆導電型を呈する半導体層を形成し、この逆導電型を呈する半導体層上に他方の電極層を形成した光電変換装置において、前記絶縁体がポリイミドからなり前記粒状結晶半導体の下部において前記逆導電型を呈する半導体層と他方の電極となる導電層との間に介在することを特徴とする。
【００１４】
上記光電変換装置では、逆導電型を呈する半導体層と前記ポリイミドからなる絶縁体との間に、導電性保護層が介在することが望ましい。
【００１５】
上記光電変換装置では、導電性保護層の膜厚が３ｎｍ以上３０ｎｍ以下であることが望ましい。
【００１６】
上記光電変換装置では、ポリイミドの硬化温度が２５０℃以下であることが望ましい。
上記光電変換装置では、ポリイミドの厚み１μｍ当たりの光吸収率が、波長４００ｎｍのとき２０％以下、波長５００ｎｍのとき２％以下であることが望ましい。
【００１７】
また上記光電変換装置では、ポリイミドからなる絶縁体の厚みが１μｍ以上であることが望ましい。
【００１８】
また、請求項７に係る光電変換装置の製造方法では、一方の電極となる基板上に一導電型を呈する粒状結晶半導体を多数配設して加熱して前記基板と接合した後、この粒状結晶半導体上に逆導電型を呈する半導体層を形成し、この粒状結晶半導体間にポリイミドを有機溶剤に溶かした溶液を塗布して２５０℃以下で熱処理することによってこの粒状結晶半導体間に絶縁体を充填し、その後この逆導電型を呈する半導体層および絶縁体上に他方の電極となる導電層を形成することを特徴とする。
【００１９】
また、請求項８に係る光電変換装置の製造方法では、一方の電極となる基板上に一導電型を呈する粒状結晶半導体を多数配設して加熱して前記基板と接合した後、この粒状結晶半導体上に逆導電型を呈する半導体層を形成し、この逆導電型を呈する半導体層の上に導電性保護層を形成し、この粒状結晶半導体間にポリイミドを有機溶剤に溶かした溶液を塗布して２５０℃以下で熱処理することによってこの粒状結晶半導体間に絶縁体を充填し、その後この導電性保護層および絶縁体上に他方の電極となる導電層を形成することを特徴とする。
上記光電変換装置の製造方法では、前記２５０℃以下での熱処理を非酸化雰囲気で行うことが望ましい。
【００２０】
上記光電変換装置の製造方法では、前記粒状結晶半導体間にポリイミドを有機溶剤に溶かした溶液を塗布する工程において、一定量のポリイミド溶液を基板上の特定の位置にスポット状もしくはライン状に塗布した後、そのポリイミド溶液を粒状結晶半導体間に浸透させることで基板全体に充填することが望ましい。
【００２１】
また上記光電変換装置の製造方法では、前記ポリイミドを有機溶剤に溶かした溶液の粘度が、固形分１０ｗｔ％の時２５℃で１００ｍＰａ・ｓ以下であることが望ましい。
【００２２】
本発明の光電変換装置によれば、基板上に粒状結晶半導体を多数配置して加熱して両者の溶融した合金部によって接合し、この多数の粒状結晶半導体上に逆導電型を呈する半導体層を形成した構造において、絶縁体が露出している基板の全面を欠陥なく覆うことで、その後形成される他方の電極となる導電層と、一方の電極となる基板との間の絶縁性を確保することができ、なお且つ絶縁体に２５０℃以下で硬化するポリイミドを用いることで、この多数の粒状結晶半導体上に形成されたＰＮ接合に熱的ダメージを与えることなく、高いＰＮ接合の品質を保ったまま絶縁層を形成できるため、従来の光電変換装置と比較して、低コストで高い変換効率を有する光電変換装置の製造が可能となる。
【００２３】
【発明の実施の形態】
以下、図面に基づいて本発明を詳細に説明する。
図１は、請求項１に係る光電変換装置の一実施形態を示す図である。図１において、１は基板、２は粒状結晶半導体、３は絶縁体、４は粒状結晶半導体２とは逆の導電型を呈する半導体層、５は導電層、１５は基板１と粒状結晶半導体２との合金層である。
また図２は、請求項２に係る光電変換装置の他の一実施形態を示す図である。図２において、６は導電性保護層である。
【００２４】
基板１は例えばアルミニウム単体もしくはアルミニウムの融点以上の融点を有する金属やセラミックを下地基板としその上にアルミニウムから成る電極層を形成した複合体を用いることができる。
【００２５】
基板１上には、図１に示すように、第一導電型の結晶半導体粒子２を多数配設する。この結晶半導体粒子２は、例えばＳｉにｐ型を呈するＢ、Ａｌ、Ｇａ等、又はｎ型を呈するＰ、Ａｓ等が微量元素含まれているものである。結晶半導体粒子２の形状としては多角形を持つもの、曲面を持つもの等があり、粒径分布としては均一、不均一を問わないが、均一の場合は粒径を揃えるための工程が必要になるため、より安価にするためには不均一な方が有利である。さらに凸曲面を持つことによって光の光線角度の依存性も小さい。
【００２６】
結晶半導体粒子２の粒径としては、０．２〜１．０ｍｍがよく、１．０ｍｍを越えると切削部も含めた従来の結晶板型の光電変換装置のシリコン使用量と変わらなくなり、結晶半導体粒子を用いるメリットがなくなる。また、０．２ｍｍよりも小さいと基板１へのアッセンブルがしにくくなるという別の問題が発生する。より好適にはシリコン使用量の関係から０．２〜０．６ｍｍがよい。
【００２７】
多数の結晶半導体粒子２を基板１上に配設する方法としては、例えば結晶半導体粒子２を基板１の表面に散布した後一定の荷重を結晶半導体粒子２上に掛けながら、基板１のアルミニウムと結晶半導体粒子２のシリコンとの共晶温度５７７℃以上に加熱することによって、基板と結晶半導体粒子の合金層１５を介して基板１と結晶半導体粒子２を接合させる方法が用いられる。
【００２８】
なお、合金層１５に接触している第１導電型の領域では、基板１の材料であるアルミニウムが拡散してｐ^＋層を形成している。しかしながら、単に導電性拡散領域を形成するのであれば、ＡｌとＳｉとの共晶温度である５７７℃以下でもできるが、基板１と粒状結晶半導体２の接合が弱いために基板１から粒状結晶半導体２が離脱し、太陽電池としての構造を維持できなくなる。
逆導電型を呈する半導体層４は例えばＳｉから成り、気相成長法等で例えばシラン化合物の気相にｎ型を呈するリン系化合物の気相、又はｐ型を呈するホウ素系化合物の気相を微量導入して形成する。形成前に粒状結晶半導体２表面のクリーニングのため、ふっ酸硝酸混合液等によるウエットエッチング処理を行うが、周囲に樹脂等の介在物がないため清浄なＰＮ接合を作製することができる。膜質としては結晶質、非晶質、結晶質と非晶質とが混在するのいずれでもよいが、光線透過率を考慮すると結晶質又は結晶質と非晶質とが混在するものがよく、光線透過率については、粒状結晶半導体２がない部分で入射光の一部が半導体層４を透過し、下部の基板１で反射して粒状結晶半導体２に照射されることで、光電変換装置全体に照射される光エネルギーを効率よく粒状結晶半導体２に照射することが可能となる。
【００２９】
導電性については、半導体層４中の微量元素の濃度は高くてもよく、例えば１×１０^１６〜１０^１９ａｔｏｍｓ／ｃｍ^３台程度である。
【００３０】
さらに、半導体層４は粒状結晶半導体２の表面に沿って形成し、粒状結晶半導体２の凸曲面形状に沿って形成することが望ましい。粒状結晶半導体２の凸曲面状の表面に沿って形成することによってｐｎ接合の面積を広くとることができ、粒状結晶半導体２の内部で生成したキャリアを効率よく収集することが可能となる。なお、その外郭にｎ型を呈するＰ、Ａｓ等、又はｐ型を呈するＢ、Ａｌ、Ｇａ等が微量含まれている粒状結晶半導体２を用いる場合には、半導体層４はなくてもよく、その上に導電層５を形成してもよい。
【００３１】
絶縁体３は、正極と負極の分離を行うための絶縁材料からなり、硬化温度が２５０℃以下、好適には２２０℃以下のポリイミドから成る。熱処理温度を２５０℃以下とすることで、すでに形成されている粒状結晶半導体２と逆導電型を呈する半導体層４との間のＰＮ接合に熱的ダメージを与えることなく粒状結晶半導体２間にポリイミド絶縁体３を充填できるので、ＰＮ接合を高品質に保つことができ、高い光電変換効率が得られる。逆に硬化温度が２５０℃より高いポリイミドではＰＮ接合への熱的ダメージで光電変換効率が劣化する。ポリイミドの硬化温度を下げるには、原料の酸成分またはアミン成分の骨格を変更してもよいし、イミド化反応を促進する塩基性の低温硬化剤を添加してもよいが、低温硬化剤を用いる場合はポリイミドの硬化過程でできるだけ揮発除去できるものを選択することが望ましい。またポリイミドの硬化温度は通常、熱分析または赤外線ピーク比から求めるイミド化率で見積もれるが、イミド化率９９％以上になる温度を実質的に硬化温度と見なす事ができる。
【００３２】
前記ポリイミドの厚み１μｍ当たりの光吸収率は、波長４００ｎｍのとき２０％以下、波長５００ｎｍのとき２％以下であることが望ましい。この条件を満たすポリイミドからなる絶縁体３は実質的に透明であり、粒状結晶半導体２上に直接照射しなかった光も、粒状結晶半導体２間に充填された絶縁体３を透過し基板１で反射後再び粒状結晶半導体２で吸収利用できる。
【００３３】
絶縁体３の厚みは１μｍ以上が望ましい。厚みが１μｍより薄くになると、絶縁性が不安定になってリーク電流が流れやすくなり耐侯性や密着性等が劣化する。
【００３４】
また、前記シロキサン骨格を含有するポリイミドは有機溶媒に溶かして用いるが、有機溶媒としては、Ｎ−メチルピロリドン、Ｎ，Ｎ’−ジメチルホルムアミド、Ｎ，Ｎ’−ジメチルアセトアミド、ｏ，ｍ，ｐ−メチルフェノール等を用いることができ、中でも溶解性、毒性、コストの観点からＮ−メチルピロリドン、Ｎ，Ｎ’−ジメチルアセトアミドが望ましい。
【００３５】
ポリイミドの塗布方法としては、ディッピング法、スピンコート法、スプレー法、スクリーン印刷法、浸透法などがあるが、できるだけ粒状結晶半導体２上に形成されている逆の導電型を呈する半導体層４の表面を汚さず、塗布量も必要最少量に留めることができる浸透法が望ましい。浸透法の一例として、例えばディスペンサーを用いて一定量のポリイミド溶液を基板１上の等間隔の特定の位置にスポット状もしくはライン状に供給し、その後塗布されたポリイミド溶液を粒状結晶半導体２間に浸透させることで基板１全体に溶液を充填させる方法が用いられる。この塗布方法により一部の粒状結晶半導体２はポリイミドで必要以上に覆われることになるが、熱処理後のポリイミドが実質的に透明であるため、その後形成される導電層５と半導体層４の一部が接合していれば、特性上ほとんど影響を受けない。
浸透法で効果的に絶縁体３を形成するためには、ポリイミド溶液の粘度は固形分１０ｗｔ％の時２５℃で１００ｍＰａ・ｓ以下、好適には６０ｍＰａ・ｓ以下、より好適には４０ｍＰａ・ｓ以下であることことが望ましい。ポリイミド絶縁体３の厚みを１μｍ以上にするためには、ポリイミド溶液の塗布濃度は固形分１０ｗｔ％以上が好ましいが、その時の粘度が１００ｍＰａ・ｓより大きいとポリイミド溶液が粒状結晶半導体２間に浸透しにくくなるため、厚みばらつきが生じ絶縁性が不安定になる。
ポリイミドの熱処理は窒素またはアルゴン雰囲気等の非酸化雰囲気で行うことが望ましい。非酸化雰囲気で熱処理することでポリイミドの光吸収率が低くなり、基板との密着性も向上する。また粒状結晶半導体２表面が露出している場合に酸化雰囲気で熱処理するとその表面に酸化物層が生成し、その後形成されるＰＮ接合面の品質を劣化させてしまう。
【００３６】
導電層５はスパッタリング法や気相成長法等の成膜方法あるいは塗布焼成等によって形成し、ＳｎＯ_２、Ｉｎ_２Ｏ_３、ＩＴＯ、ＺｎＯ、ＴｉＯ_２等から選ばれる１種又は複数の酸化物系膜、又はＴｉ、Ｐｔ、Ａｕ等から選ばれる１種又は複数の金属系膜を形成する。なお、このような導電層５は透明であることが必要であり、粒状結晶半導体２がない部分で入射光の一部が導電層５を透過し、下部の基板１で反射して粒状結晶半導体２に照射されることで、光電変換装置全体に照射される光エネルギーを効率よく粒状結晶半導体２に照射することが可能となる。
【００３７】
導電層５は膜厚を選べば反射防止膜としての効果も期待できる。さらに、導電層５は半導体層４あるいは粒状結晶半導体２の表面に沿って形成し、粒状結晶半導体２の凸曲面形状に沿って形成することが望ましい。粒状結晶半導体２の凸曲面状の表面に沿って形成することによってｐｎ接合の面積を広くとることができ、粒状結晶半導体２の内部で生成したキャリアを効率よく収集することが可能となる。
図２における導電性保護層６は、半導体層４の熱的ダメージまたは汚染により、その上に形成される導電層５とのオーミック接触がとれなくなることを防止するために半導体層４上に設けた導電性材料からなる薄膜である。導電性材料としては導電層５と同一でもまた異なっていてもかまわないが、実質的に透明であることが望ましい。また導電層５と同様にスパッタリング法や気相成長法等の成膜方法あるいは塗布焼成等によって形成することができる。膜厚は３〜３０ｎｍが望ましい。膜厚が３ｎｍより薄いと半導体層４の保護層としての役目を果たさないし、３０ｎｍより厚いとその上に形成される他方の電極となる導電層５と基板１との間でのショートの原因となる。
【００３８】
また半導体層４あるいは導電層５上に保護層（不図示）を形成してもよい。このような保護層としては透明誘電体の特性を持つものがよく、ＣＶＤ法やＰＶＤ法等で例えば酸化珪素、酸化セシウム、酸化アルミニウム、窒化珪素、酸化チタン、ＳｉＯ_２−ＴｉＯ_２、酸化タンタル、酸化イットリウム等を単一組成又は複数組成で単層又は組み合わせて半導体層４又は導電層５上に形成する。保護層は、光の入射面に設けられるために、透明性が必要であり、また半導体層４又は導電層５と外部との間のリークを防止するために、誘電体であることが必要である。なお、保護層の膜厚を最適化すれば反射防止膜としての機能も期待できる。
【００３９】
また、直列抵抗値を低くするために、半導体層４又は導電層５の上に一定間隔のフィンガーやバスバーといったパターン電極（不図示）を設けて直接的又は間接的に半導体層４と接続し、変換効率を向上させることも可能である。
【００４０】
【実施例】
次に、本発明の光電変換装置の実施例を説明する。
〔実施例１〕
アルミニウム基板１上に直径０．３〜０．５ｍｍのｐ型シリコン粒子２を多数設置した後、ｐ型シリコン粒子２が動かないように一定の荷重をかけて押し付けた状態で、Ｎ_２−Ｈ_２雰囲気中の６３０℃で１０分間加熱処理してｐ型シリコン粒子２をアルミニウム基板１に接合させた（接合部１５）。
【００４１】
次にｐ型シリコン粒子２の上部表面をクリーニングするために、この基板１を弗酸硝酸混合液（ＨＦ：ＨＮＯ_３＝１：２０）に１分間浸漬して純水で十分洗浄した後、シランガスと微量のＰ化合物からなる混合ガスを用いたプラズマＣＶＤ法により、ｐ型シリコン粒子２上に厚み２０ｎｍのｎ型非晶質シリコン半導体層４を成膜した。
硬化温度が２３０℃であるポリイミド樹脂のＮ−メチルピロリドン溶液１２ｗｔ％品（１０ｗｔ％希釈時の２５℃での粘度は５０ｍＰａ・ｓ）を、上記シリコン粒子２を接合したアルミニウム基板１上にディスペンサーを用いた浸透法で塗布した。その後窒素雰囲気下２５０℃−１時間加熱処理しｐ型シリコン粒子２間のアルミニウム基板１上にポリイミド樹脂の絶縁層３を形成した。得られた絶縁層３の厚みはアルミニウム基板１上で２〜５μｍであった。
また上記ポリイミドをガラス基板に塗布し窒素雰囲気下２５０℃−１時間加熱処理した後、光吸収率を測定したところ、厚み１μｍ当たりの光吸収率が、波長４００ｎｍのとき１５％、波長５００ｎｍのとき１％であった。
【００４２】
次に、その上にスパッタリング法によって厚み１００ｎｍのＩＴＯ膜による導電層５を作製した。
【００４３】
フィンガーおよびバスバーからなるパターン電極を設けた後、光電変換率を測定したところ、８．３％と比較的高い値が得られた。また、この試料に対し−４０℃〜９０℃の温度サイクル試験５００サイクルを行ったところ、絶縁体３にクラック、剥がれ等は発生せず、光電変換率も８．１％と特性劣化はほとんど見られなかった。
〔実施例２〕
プラズマＣＶＤ法により、ｐ型シリコン粒子２上に厚み２０ｎｍのｎ型非晶質シリコン半導体層４を成膜した後、その上にスパッタリング法によって厚み１０ｎｍのＩＴＯ膜による導電性保護膜６を作製した他は実施例１と同様にして光電変換装置を作製した。得られた絶縁層３の厚みは実施例１と同等であった。光電変換率を測定したところ、８．５％と比較的高い値が得られた。また、この試料に対し−４０℃〜９０℃の温度サイクル試験５００サイクルを行ったところ、絶縁体３にクラック、剥がれ等は発生せず、光電変換率も８．４％と特性劣化はほとんど見られなかった。
【００４４】
【発明の効果】
以上のように、請求項１に係る光電変換装置によれば、基板に接合した粒状結晶半導体上に逆導電型を呈する半導体層を形成し、その上に導電層を形成した構造において、ポリイミドからなる絶縁体をその粒状結晶半導体の下部において逆導電型を呈する半導体層と導電層の間に介在させることから、粒状結晶半導体上に清浄な広いＰＮ接合面を確保でき、よって従来の光電変換装置と比較して、低コストで高い変換効率を有する光電変換装置の製造が可能となる。
【００４５】
また、請求項７に係る光電変換装置の製造方法によれば、粒状結晶半導体上に逆導電型を呈する半導体層を形成した後、ポリイミドを有機溶剤に溶かした溶液を塗布し非酸化性雰囲気下２５０℃以下で熱処理することによってこの粒状結晶半導体間にポリイミド絶縁体を充填することから、粒状結晶半導体上に形成されたＰＮ接合に熱的ダメージを与えることなく高いＰＮ接合の品質を保ったまま絶縁層を形成でき、従来の光電変換装置と比較して、低コストで高い変換効率を有する光電変換装置の製造が可能となる。
【図面の簡単な説明】
【図１】本発明の光電変換装置の一実施形態を示す断面図である。
【図２】本発明の光電変換装置の他の一実施形態を示す断面図である。
【図３】従来例１の光電変換装置を示す断面図である。
【図４】従来例２の光電変換装置を示す断面図である。
【図５】従来例３の光電変換装置を示す断面図である。
【図６】従来例４の光電変換装置を示す断面図である。
【符号の説明】
１・・・・基板
２・・・・一導電型を呈する粒状結晶半導体
３・・・・絶縁体
４・・・・逆導電型を呈する半導体層
５・・・・導電層
６・・・・導電性保護層
１５・・・アルミニウムとシリコンとの合金層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a photoelectric conversion device used for photovoltaic power generation and the like and a method of manufacturing the same, and more particularly, to a photoelectric conversion device using a granular crystal semiconductor and a method of manufacturing the same.
[0002]
[Prior art]
FIGS. 3 to 6 show a photoelectric conversion device using a conventional granular crystal semiconductor. For example, as shown in FIG. 3, an opening is formed in the first aluminum foil 9, and a silicon ball 2 having an n-type skin portion 8 on a p-type is inserted into the opening. The n-type skin portion 8 is removed, the oxide insulating layer 3 is formed on the back side of the first aluminum foil 9, the oxide insulating layer 3 on the back side of the silicon sphere 2 is removed, and the silicon sphere 2 and the second A photoelectric conversion device that joins an aluminum foil 7 is disclosed (for example, see Patent Document 1).
[0003]
As shown in FIG. 4, a low melting point metal layer 10 is formed on a substrate 1, and a first conductivity type granular crystal semiconductor 2 is disposed on the low melting point metal layer 10. A photoelectric conversion device in which an amorphous semiconductor layer 6 of the second conductivity type is formed between the low-melting metal layer 10 and the low-melting metal layer 10 via an insulating layer 3 (see, for example, Patent Document 2).
[0004]
As shown in FIG. 5, a high melting point metal layer 11, a low melting point metal layer 10, and semiconductor fine crystal grains 12 are deposited on the substrate 1, and the semiconductor fine crystal grains 12 are melted and saturated, and then gradually. A method of forming a polycrystalline thin film 12 by cooling a semiconductor to liquid phase epitaxial growth (see, for example, Patent Document 3).
[0005]
As shown in FIG. 6, a plurality of first conductive type spherical semiconductors 16 are buried in a thermoplastic transparent flexible resin 17 in a state of being bonded by a conductive paste 14 on a sheet-shaped module substrate 1, A method of forming a surface layer 4 of the second conductivity type by doping impurities into the surface region of the semiconductor 16 by thermal diffusion or ion implantation is disclosed (for example, see Patent Document 4).
[0006]
In FIGS. 4, 5, and 6, reference numeral 5 denotes an electrode made of a transparent conductive film or the like.
[0007]
[Patent Document 1]
JP-A-61-124179 [Patent Document 2]
Japanese Patent No. 2641800 [Patent Document 3]
Japanese Patent Publication No. 8-34177 [Patent Document 4]
JP 2001-230429 A
[Problems to be solved by the invention]
However, in the photoelectric conversion device as shown in FIG. 3, it is necessary to form an opening in the first aluminum foil 9 and push the silicon sphere 2 into the opening to join the silicon sphere 2 to the first aluminum foil 9. Therefore, there has been a problem that uniformity is required for the diameter of the silicon sphere 2 and the cost is high. Further, since the processing temperature at the time of joining is 577 ° C. or lower, which is the eutectic temperature of aluminum and silicon, there is a problem that the joining becomes unstable.
[0009]
Further, according to the photoelectric conversion device as shown in FIG. 4, since the amorphous semiconductor layer 6 of the second conductivity type is provided on the granular semiconductor 2 of the first conductivity type, the amorphous semiconductor layer is required to form a stable pn junction. Before the layer 6 was formed, it was necessary to sufficiently etch and clean the surface of the granular crystal semiconductor 2. Further, the film thickness must be reduced due to the large light absorption of the amorphous semiconductor layer 6, and when the film thickness of the amorphous semiconductor layer 6 is small, tolerance for defects is reduced, and the cleaning process and the manufacturing environment are reduced. Has to be strictly managed, and as a result, there is a problem that the cost is high.
[0010]
Further, according to the photoelectric conversion device as shown in FIG. 5, since the low melting point metal layer 10 is mixed into the liquid-phase epitaxial polycrystalline layer 12 of the first conductivity type, the performance is deteriorated. There is a problem that a leak occurs between the upper electrode 5 and the lower electrode 11.
[0011]
Further, according to the photoelectric conversion device as shown in FIG. 6, since the high-concentration layer does not exist at the junction of the first conductive type spherical semiconductor 16 and the conductive paste 14, the barrier of electrons excited by photons is obtained. It was found that the so-called backfield effect could not be obtained and the photoelectric conversion efficiency was reduced.
[0012]
The present invention has been made in view of the above-mentioned problems of the related art, and an object of the present invention is to provide a low-cost, high-performance, highly reliable photoelectric conversion device and a method of manufacturing the same.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, a photoelectric conversion device according to claim 1 has a structure in which a large number of granular crystal semiconductors exhibiting one conductivity type are arranged on a substrate serving as one electrode, and an insulator is interposed between the granular crystal semiconductors. Forming a semiconductor layer exhibiting the opposite conductivity type on the granular crystal semiconductor, and forming the other electrode layer on the semiconductor layer exhibiting the opposite conductivity type. The semiconductor device is characterized in that it is interposed between the semiconductor layer having the opposite conductivity type and the conductive layer serving as the other electrode below the crystalline semiconductor.
[0014]
In the above photoelectric conversion device, it is desirable that a conductive protective layer be interposed between the semiconductor layer having the opposite conductivity type and the insulator made of the polyimide.
[0015]
In the above photoelectric conversion device, it is preferable that the thickness of the conductive protective layer be 3 nm or more and 30 nm or less.
[0016]
In the above photoelectric conversion device, the curing temperature of the polyimide is desirably 250 ° C. or lower.
In the above-mentioned photoelectric conversion device, it is desirable that the light absorptivity per 1 μm thickness of the polyimide is 20% or less when the wavelength is 400 nm and 2% or less when the wavelength is 500 nm.
[0017]
In the above-mentioned photoelectric conversion device, it is desirable that the thickness of the insulator made of polyimide is 1 μm or more.
[0018]
Further, in the method for manufacturing a photoelectric conversion device according to claim 7, a large number of granular semiconductors exhibiting one conductivity type are provided on a substrate serving as one electrode, and the granular crystal semiconductor is heated and joined to the substrate. A semiconductor layer having a reverse conductivity type is formed on a semiconductor, a solution of polyimide dissolved in an organic solvent is applied between the granular crystal semiconductors, and heat treatment is performed at 250 ° C. or less to fill an insulator between the granular crystal semiconductors. Then, a conductive layer serving as the other electrode is formed over the semiconductor layer having the opposite conductivity type and the insulator.
[0019]
In the method of manufacturing a photoelectric conversion device according to claim 8, a large number of granular semiconductors exhibiting one conductivity type are provided on a substrate to be one of the electrodes, heated, and bonded to the substrate. A semiconductor layer having the opposite conductivity type is formed on the semiconductor, a conductive protection layer is formed on the semiconductor layer having the opposite conductivity type, and a solution in which polyimide is dissolved in an organic solvent is applied between the granular crystal semiconductors. And filling the insulator between the granular crystal semiconductors by heat treatment at 250 ° C. or lower, and then forming a conductive layer to be the other electrode on the conductive protective layer and the insulator.
In the method for manufacturing a photoelectric conversion device, it is preferable that the heat treatment at 250 ° C. or lower be performed in a non-oxidizing atmosphere.
[0020]
In the method for manufacturing a photoelectric conversion device, in the step of applying a solution of polyimide dissolved in an organic solvent between the granular crystal semiconductors, a certain amount of the polyimide solution is applied in a spot or line at a specific position on the substrate. Thereafter, it is desirable to fill the entire substrate by infiltrating the polyimide solution between the granular crystal semiconductors.
[0021]
In the method for manufacturing a photoelectric conversion device, it is desirable that the viscosity of the solution obtained by dissolving the polyimide in an organic solvent is 100 mPa · s or less at 25 ° C. when the solid content is 10 wt%.
[0022]
According to the photoelectric conversion device of the present invention, a large number of granular crystal semiconductors are arranged on a substrate, heated and joined by a molten alloy portion of the two, and a semiconductor layer exhibiting a reverse conductivity type is formed on the large number of granular crystal semiconductors. In the formed structure, by covering the entire surface of the substrate where the insulator is exposed without defects, the insulating property between the subsequently formed conductive layer serving as the other electrode and the substrate serving as one electrode is ensured. By using a polyimide that cures at 250 ° C. or lower for the insulator, high quality PN junctions can be maintained without thermally damaging the PN junctions formed on the large number of granular crystal semiconductors. Since the insulating layer can be formed as it is, a photoelectric conversion device having low conversion cost and high conversion efficiency can be manufactured as compared with a conventional photoelectric conversion device.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing one embodiment of the photoelectric conversion device according to claim 1. In FIG. 1, reference numeral 1 denotes a substrate, 2 denotes a granular crystal semiconductor, 3 denotes an insulator, 4 denotes a semiconductor layer having a conductivity type opposite to that of the granular crystal semiconductor 2, 5 denotes a conductive layer, and 15 denotes the substrate 1 and the granular crystal semiconductor 2 And an alloy layer.
FIG. 2 is a diagram showing another embodiment of the photoelectric conversion device according to the second aspect. In FIG. 2, reference numeral 6 denotes a conductive protective layer.
[0024]
As the substrate 1, for example, aluminum alone or a composite in which a metal or a ceramic having a melting point equal to or higher than the melting point of aluminum is used as a base substrate and an electrode layer made of aluminum is formed thereon can be used.
[0025]
As shown in FIG. 1, a large number of crystalline semiconductor particles 2 of the first conductivity type are arranged on a substrate 1. The crystalline semiconductor particles 2 contain, for example, a trace element of Si such as B, Al, Ga or the like exhibiting p-type, or P or As exhibiting n-type. The crystalline semiconductor particles 2 may have a polygonal shape, a curved shape, or the like. The particle size distribution may be uniform or non-uniform, but if uniform, a process for uniforming the particle size is required. Therefore, the non-uniformity is advantageous in order to reduce the cost. Further, by having a convex curved surface, the dependence on the light ray angle of light is small.
[0026]
The grain size of the crystalline semiconductor particles 2 is preferably 0.2 to 1.0 mm. If the grain size exceeds 1.0 mm, the amount of silicon used in the conventional crystal plate-type photoelectric conversion device including the cut portion does not change. The merit of using particles is lost. Further, if it is smaller than 0.2 mm, another problem that it is difficult to assemble the substrate 1 occurs. More preferably, the thickness is 0.2 to 0.6 mm in view of the amount of silicon used.
[0027]
As a method of disposing a large number of crystalline semiconductor particles 2 on the substrate 1, for example, after dispersing the crystalline semiconductor particles 2 on the surface of the substrate 1, while applying a certain load on the crystalline semiconductor particles 2, A method is used in which the substrate 1 is bonded to the crystal semiconductor particles 2 via the alloy layer 15 of the substrate and the crystal semiconductor particles by heating the crystal semiconductor particles 2 to a eutectic temperature of 577 ° C. or more with silicon.
[0028]
In the first conductivity type region in contact with the alloy layer 15, aluminum as a material of the substrate 1 is diffused to form ap ⁺ layer. However, if the conductive diffusion region is simply formed, the temperature can be lowered to 577 ° C. or lower, which is the eutectic temperature of Al and Si. However, since the bonding between the substrate 1 and the granular crystal semiconductor 2 is weak, the granular crystal semiconductor 2 comes off, and the structure as a solar cell cannot be maintained.
The semiconductor layer 4 having the opposite conductivity type is made of, for example, Si. For example, a gaseous phase of a silane compound is converted into a gaseous phase of a phosphorus-based compound having n-type or a gaseous phase of a boron-based compound having p-type by a vapor phase growth method or the like. Formed by introducing a small amount. Before the formation, the surface of the granular crystal semiconductor 2 is cleaned by wet etching using a mixed solution of hydrofluoric / nitric acid or the like, but a clean PN junction can be produced because there is no inclusion such as resin around. The film quality may be any of crystalline, amorphous, and a mixture of crystalline and amorphous, but considering the light transmittance, a crystalline or a mixture of crystalline and amorphous is preferable. Regarding the transmittance, a part of the incident light passes through the semiconductor layer 4 in a portion where the granular crystal semiconductor 2 does not exist, is reflected by the substrate 1 below, and is irradiated on the granular crystal semiconductor 2, so that the entire photoelectric conversion device is irradiated. It is possible to efficiently irradiate the granular crystal semiconductor 2 with the irradiated light energy.
[0029]
Concerning the conductivity, the concentration of the trace element in the semiconductor layer 4 may be high, for example, about 1 × 10 ¹⁶ to 10 ¹⁹ atoms / cm ³ .
[0030]
Further, it is desirable that the semiconductor layer 4 is formed along the surface of the granular crystal semiconductor 2 and is formed along the convex curved surface shape of the granular crystal semiconductor 2. By forming the pn junction along the convex curved surface of the granular crystal semiconductor 2, the area of the pn junction can be widened, and the carriers generated inside the granular crystal semiconductor 2 can be efficiently collected. When the granular crystal semiconductor 2 containing a small amount of P, As, or the like exhibiting n-type, or B, Al, Ga, or the like exhibiting p-type on its outer surface, the semiconductor layer 4 may be omitted. The conductive layer 5 may be formed thereon.
[0031]
The insulator 3 is made of an insulating material for separating the positive electrode and the negative electrode, and is made of polyimide having a curing temperature of 250 ° C. or less, preferably 220 ° C. or less. By setting the heat treatment temperature to 250 ° C. or less, the polyimide can be formed between the granular crystal semiconductors 2 without thermally damaging the PN junction between the already formed granular crystal semiconductor 2 and the semiconductor layer 4 having the opposite conductivity type. Since the insulator 3 can be filled, the PN junction can be maintained at high quality, and high photoelectric conversion efficiency can be obtained. Conversely, with polyimide having a curing temperature higher than 250 ° C., the photoelectric conversion efficiency is deteriorated due to thermal damage to the PN junction. To lower the curing temperature of the polyimide, the skeleton of the acid component or the amine component of the raw material may be changed, or a basic low-temperature curing agent that promotes the imidization reaction may be added. When used, it is desirable to select one that can be volatilized and removed as much as possible during the curing process of the polyimide. The curing temperature of the polyimide is usually estimated by an imidization ratio obtained from thermal analysis or an infrared peak ratio, but a temperature at which the imidization ratio is 99% or more can be substantially regarded as a curing temperature.
[0032]
It is desirable that the light absorptivity of the polyimide per 1 μm thickness is 20% or less at a wavelength of 400 nm and 2% or less at a wavelength of 500 nm. The insulator 3 made of polyimide that satisfies this condition is substantially transparent, so that light that has not been directly irradiated onto the granular crystal semiconductor 2 passes through the insulator 3 filled between the granular crystal semiconductors 2 and passes through the substrate 1. After reflection, it can be absorbed and utilized again by the granular crystal semiconductor 2.
[0033]
The thickness of the insulator 3 is desirably 1 μm or more. When the thickness is less than 1 μm, the insulating property becomes unstable, a leak current easily flows, and the weather resistance, the adhesion and the like deteriorate.
[0034]
The polyimide containing the siloxane skeleton is used by dissolving it in an organic solvent. Examples of the organic solvent include N-methylpyrrolidone, N, N'-dimethylformamide, N, N'-dimethylacetamide, o, m, p- Methyl phenol and the like can be used, and among them, N-methylpyrrolidone and N, N'-dimethylacetamide are desirable from the viewpoint of solubility, toxicity and cost.
[0035]
Examples of the method for applying the polyimide include a dipping method, a spin coating method, a spray method, a screen printing method, and a penetration method. The surface of the semiconductor layer 4 having the opposite conductivity type formed on the granular crystal semiconductor 2 as much as possible. It is desirable to use a permeation method which can keep the amount of application to a minimum necessary amount without soiling the surface. As an example of the infiltration method, for example, a fixed amount of a polyimide solution is supplied in a spot or line form to a specific position at equal intervals on the substrate 1 using a dispenser, and then the applied polyimide solution is placed between the granular crystal semiconductors 2. A method of filling the entire substrate 1 with a solution by infiltration is used. By this coating method, a part of the granular crystal semiconductor 2 is unnecessarily covered with the polyimide. However, since the polyimide after the heat treatment is substantially transparent, a part of the conductive layer 5 and the semiconductor layer 4 which are formed thereafter is formed. If the parts are joined, there is almost no effect on the characteristics.
In order to effectively form the insulator 3 by the infiltration method, the viscosity of the polyimide solution at 25 ° C. when the solid content is 10 wt% is 100 mPa · s or less, preferably 60 mPa · s or less, more preferably 40 mPa · s or less. It is desirable that: In order to make the thickness of the polyimide insulator 3 1 μm or more, the coating concentration of the polyimide solution is preferably 10 wt% or more, but if the viscosity at that time is more than 100 mPa · s, the polyimide solution penetrates between the granular crystal semiconductors 2. As a result, thickness variation occurs and the insulation becomes unstable.
The heat treatment of the polyimide is preferably performed in a non-oxidizing atmosphere such as a nitrogen or argon atmosphere. By performing the heat treatment in a non-oxidizing atmosphere, the light absorption of the polyimide is reduced, and the adhesion to the substrate is also improved. Further, if the heat treatment is performed in an oxidizing atmosphere when the surface of the granular crystal semiconductor 2 is exposed, an oxide layer is generated on the surface, and the quality of the PN junction surface formed thereafter deteriorates.
[0036]
The conductive layer 5 is formed by a film formation method such as a sputtering method or a vapor phase growth method, or by coating and baking, and is formed of one or more oxides selected from SnO ₂ , In ₂ O ₃ , ITO, ZnO, TiO _{2, and the} like. A film or one or more metal-based films selected from Ti, Pt, Au and the like are formed. Note that such a conductive layer 5 needs to be transparent, and a part of the incident light passes through the conductive layer 5 in a portion where the granular crystal semiconductor 2 is not present, and is reflected by the lower substrate 1 so that the granular crystal semiconductor 2, the granular crystal semiconductor 2 can be efficiently irradiated with light energy applied to the entire photoelectric conversion device.
[0037]
If the thickness of the conductive layer 5 is selected, an effect as an antireflection film can be expected. Further, it is desirable that the conductive layer 5 be formed along the surface of the semiconductor layer 4 or the granular crystal semiconductor 2 and to be formed along the convex curved surface shape of the granular crystal semiconductor 2. By forming the pn junction along the convex curved surface of the granular crystal semiconductor 2, the area of the pn junction can be widened, and the carriers generated inside the granular crystal semiconductor 2 can be efficiently collected.
The conductive protective layer 6 in FIG. 2 is provided on the semiconductor layer 4 in order to prevent the semiconductor layer 4 from being in ohmic contact with the conductive layer 5 formed thereon due to thermal damage or contamination. It is a thin film made of a conductive material. The conductive material may be the same as or different from the conductive layer 5, but is preferably substantially transparent. Similarly to the conductive layer 5, the conductive layer 5 can be formed by a film forming method such as a sputtering method or a vapor phase growth method, or by coating and firing. The thickness is desirably 3 to 30 nm. If the film thickness is smaller than 3 nm, the semiconductor layer 4 does not serve as a protective layer. If the film thickness is larger than 30 nm, a short circuit between the conductive layer 5 serving as the other electrode formed thereon and the substrate 1 may be caused. Become.
[0038]
Further, a protective layer (not shown) may be formed on the semiconductor layer 4 or the conductive layer 5. As such a protective layer, a material having the property of a transparent dielectric material is preferable. For example, silicon oxide, cesium oxide, aluminum oxide, silicon nitride, titanium oxide, SiO ₂ —TiO ₂ , tantalum oxide, A single layer or a combination of yttrium oxide or the like with a single composition or a plurality of compositions is formed on the semiconductor layer 4 or the conductive layer 5. The protective layer needs to be transparent in order to be provided on the light incident surface, and needs to be a dielectric in order to prevent leakage between the semiconductor layer 4 or the conductive layer 5 and the outside. is there. If the thickness of the protective layer is optimized, a function as an antireflection film can be expected.
[0039]
Further, in order to reduce the series resistance, a pattern electrode (not shown) such as a finger or a bus bar is provided at regular intervals on the semiconductor layer 4 or the conductive layer 5 and connected directly or indirectly to the semiconductor layer 4. It is also possible to improve the conversion efficiency.
[0040]
【Example】
Next, an embodiment of the photoelectric conversion device of the present invention will be described.
[Example 1]
After a large number of p-type silicon particles 2 having a diameter of 0.3 to 0.5 mm are placed on an aluminum substrate 1, N ₂ -H is pressed while applying a constant load so that the p-type silicon particles 2 do not move. _The heat treatment was performed at 630 ° C. in _two atmospheres for 10 minutes to bond the p-type silicon particles 2 to the aluminum substrate 1 (joining portion 15).
[0041]
Next, in order to clean the upper surface of the p-type silicon particles 2, the substrate 1 is immersed in a mixed solution of hydrofluoric and nitric acid (HF: HNO ₃ = 1: 20) for 1 minute, sufficiently washed with pure water, and then subjected to silane gas. An n-type amorphous silicon semiconductor layer 4 having a thickness of 20 nm was formed on the p-type silicon particles 2 by a plasma CVD method using a mixed gas comprising P and a small amount of a P compound.
A 12 wt% N-methylpyrrolidone solution of a polyimide resin having a curing temperature of 230 ° C. (viscosity at 25 ° C. when diluted at 10 wt% is 50 mPa · s) was placed on an aluminum substrate 1 to which the silicon particles 2 were bonded by dispensing. It was applied by the penetration method used. Thereafter, heat treatment was performed at 250 ° C. for 1 hour in a nitrogen atmosphere to form an insulating layer 3 of a polyimide resin on the aluminum substrate 1 between the p-type silicon particles 2. The thickness of the obtained insulating layer 3 was 2 to 5 μm on the aluminum substrate 1.
The polyimide was coated on a glass substrate and heated at 250 ° C. for 1 hour in a nitrogen atmosphere, and then the light absorption was measured. The light absorption per 1 μm thickness was 15% when the wavelength was 400 nm and when the wavelength was 500 nm. 1%.
[0042]
Next, a conductive layer 5 of an ITO film having a thickness of 100 nm was formed thereon by a sputtering method.
[0043]
After the provision of the pattern electrodes including the fingers and the bus bars, the photoelectric conversion rate was measured. As a result, a relatively high value of 8.3% was obtained. Further, when this sample was subjected to 500 cycles of a temperature cycle test at −40 ° C. to 90 ° C., no cracks or peeling occurred on the insulator 3, and the photoelectric conversion rate was 8.1%. I couldn't.
[Example 2]
After forming an n-type amorphous silicon semiconductor layer 4 having a thickness of 20 nm on the p-type silicon particles 2 by a plasma CVD method, a conductive protection film 6 of an ITO film having a thickness of 10 nm was formed thereon by a sputtering method. Otherwise, a photoelectric conversion device was manufactured in the same manner as in Example 1. The thickness of the obtained insulating layer 3 was equal to that of Example 1. When the photoelectric conversion rate was measured, a relatively high value of 8.5% was obtained. When this sample was subjected to 500 cycles of a temperature cycle test at −40 ° C. to 90 ° C., no cracks or peeling occurred on the insulator 3 and the photoelectric conversion ratio was 8.4%, indicating almost no characteristic deterioration. I couldn't.
[0044]
【The invention's effect】
As described above, according to the photoelectric conversion device according to claim 1, a semiconductor layer having an opposite conductivity type is formed on a granular crystal semiconductor bonded to a substrate, and a conductive layer is formed thereon. The insulator is interposed between the semiconductor layer having the opposite conductivity type and the conductive layer below the granular crystal semiconductor, so that a clean and wide PN junction surface can be secured on the granular crystal semiconductor. As compared with, a photoelectric conversion device having high conversion efficiency at low cost can be manufactured.
[0045]
Further, according to the method for manufacturing a photoelectric conversion device according to claim 7, after forming a semiconductor layer having a reverse conductivity type on the granular crystal semiconductor, a solution in which polyimide is dissolved in an organic solvent is applied to the semiconductor layer under a non-oxidizing atmosphere. Since the polyimide insulator is filled between the granular crystal semiconductors by performing heat treatment at a temperature of 250 ° C. or less, a high PN junction quality is maintained without thermally damaging the PN junction formed on the granular crystal semiconductor. Since an insulating layer can be formed, a photoelectric conversion device having high conversion efficiency and low cost can be manufactured as compared with a conventional photoelectric conversion device.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing one embodiment of a photoelectric conversion device of the present invention.
FIG. 2 is a sectional view showing another embodiment of the photoelectric conversion device of the present invention.
FIG. 3 is a cross-sectional view illustrating a photoelectric conversion device of Conventional Example 1.
FIG. 4 is a cross-sectional view illustrating a photoelectric conversion device of Conventional Example 2.
FIG. 5 is a cross-sectional view illustrating a photoelectric conversion device of Conventional Example 3.
FIG. 6 is a cross-sectional view illustrating a photoelectric conversion device of Conventional Example 4.
[Explanation of symbols]
1, a substrate 2, a granular crystal semiconductor 3 having one conductivity type, an insulator 4, a semiconductor layer 5 having an opposite conductivity type, a conductive layer 6, and the like. Conductive protective layer 15: alloy layer of aluminum and silicon

Claims

A large number of granular crystal semiconductors having one conductivity type are arranged on a substrate serving as one electrode, an insulator is interposed between the granular crystal semiconductors, and a semiconductor layer having a reverse conductivity type is formed on the granular crystal semiconductors. A photoelectric conversion device in which the other electrode layer is formed on the semiconductor layer having the opposite conductivity type, wherein the insulator is made of polyimide, and the semiconductor layer having the opposite conductivity type and the other electrode are formed below the granular crystal semiconductor. A photoelectric conversion device interposed between the conductive layer and the conductive layer.

The photoelectric conversion device according to claim 1, wherein a conductive protective layer is interposed between the semiconductor layer having the opposite conductivity type and the insulator made of the polyimide.

The photoelectric conversion device according to claim 2, wherein a thickness of the conductive protective layer is 3 nm or more and 30 nm or less.

The photoelectric conversion device according to claim 1, wherein a curing temperature of the polyimide is 250 ° C. or less.

5. The photoelectric conversion device according to claim 1, wherein the polyimide has an optical absorptance per 1 μm thickness of 20% or less at a wavelength of 400 nm and 2% or less at a wavelength of 500 nm. 6.

6. The photoelectric conversion device according to claim 1, wherein the thickness of the insulator made of polyimide is 1 μm or more.

After arranging a large number of granular crystal semiconductors exhibiting one conductivity type on a substrate serving as one electrode and heating and joining the substrate to the substrate, a semiconductor layer exhibiting an opposite conductivity type is formed on the granular crystal semiconductors. An insulator is filled between the granular crystal semiconductors by applying a solution of polyimide in an organic solvent between the granular crystal semiconductors and heat-treating the same at a temperature of 250 ° C. or less. Forming a conductive layer to be the other electrode on the substrate.

After arranging a large number of granular crystal semiconductors exhibiting one conductivity type on a substrate serving as one electrode and heating and joining the substrate to the substrate, a semiconductor layer exhibiting an opposite conductivity type is formed on the granular crystal semiconductors. A conductive protective layer is formed on the semiconductor layer having the opposite conductivity type, and a solution in which polyimide is dissolved in an organic solvent is applied between the granular crystal semiconductors and heat-treated at 250 ° C. or lower. A method for manufacturing a photoelectric conversion device, comprising filling an insulator, and then forming a conductive layer serving as the other electrode over the conductive protective layer and the insulator.

The method according to claim 7, wherein the heat treatment at 250 ° C. or lower is performed in a non-oxidizing atmosphere.

In the step of applying a solution in which polyimide is dissolved in an organic solvent between the granular crystal semiconductors, after applying a certain amount of the polyimide solution in a spot or line at a specific position on the substrate, the polyimide solution is applied to the granular crystal semiconductor. The method for manufacturing a photoelectric conversion device according to claim 7, wherein the entire substrate is filled by infiltrating into the gap.

The method according to claim 10, wherein the viscosity of the solution obtained by dissolving the polyimide in an organic solvent is 100 mPa · s or less at 25 ° C at a solid content of 10 wt%.