薄膜太陽能電池原理

在(zai)化(hua)(hua)(hua)學(xue)電(dian)(dian)池中(zhong)，化(hua)(hua)(hua)學(xue)能(neng)直(zhi)接轉變為電(dian)(dian)能(neng)是(shi)靠電(dian)(dian)池內部自發進行氧(yang)化(hua)(hua)(hua)、還(huan)原(yuan)(yuan)等(deng)化(hua)(hua)(hua)學(xue)反應的(de)(de)結(jie)果(guo)，這種(zhong)反應分別在(zai)兩個電(dian)(dian)極上進行。負極活(huo)性(xing)物質(zhi)由(you)電(dian)(dian)位較(jiao)負并在(zai)電(dian)(dian)解質(zhi)中(zhong)穩(wen)定(ding)(ding)的(de)(de)還(huan)原(yuan)(yuan)劑組(zu)成，如鋅(xin)、鎘(ge)、鉛等(deng)活(huo)潑(po)金(jin)屬(shu)和氫或碳氫化(hua)(hua)(hua)合物等(deng)。正(zheng)極活(huo)性(xing)物質(zhi)由(you)電(dian)(dian)位較(jiao)正(zheng)并在(zai)電(dian)(dian)解質(zhi)中(zhong)穩(wen)定(ding)(ding)的(de)(de)氧(yang)化(hua)(hua)(hua)劑組(zu)成，如二氧(yang)化(hua)(hua)(hua)錳、二氧(yang)化(hua)(hua)(hua)鉛、氧(yang)化(hua)(hua)(hua)鎳等(deng)金(jin)屬(shu)氧(yang)化(hua)(hua)(hua)物，氧(yang)或空氣，鹵素及其鹽類，含氧(yang)酸(suan)及其鹽類等(deng)。

電解質則是具有良好離子導電性的材料，如酸、堿、鹽的水溶液，有機或無機非水溶液、熔融鹽或固體電解質等。當外電路斷開時，兩極之間雖然有電位差(開路(lu)電壓)，但沒有電(dian)流(liu)，存(cun)儲在(zai)電(dian)池中的化學能(neng)并不轉換為(wei)電(dian)能(neng)。當(dang)外電(dian)路(lu)閉(bi)合時，在(zai)兩電(dian)極電(dian)位差的作用(yong)下即有電(dian)流(liu)流(liu)過外電(dian)路(lu)。

同時在電(dian)池內(nei)部，由于電(dian)解質中不(bu)存(cun)在自由電(dian)子，電(dian)荷的傳(chuan)遞必然伴隨兩極活性物質與電(dian)解質界(jie)面的氧化或(huo)還原反應(ying)，以及反應(ying)物和反應(ying)產物的物質遷移。電(dian)(dian)(dian)荷在電(dian)(dian)(dian)解質中的(de)(de)傳(chuan)遞也要由離子的(de)(de)遷移(yi)來(lai)完成(cheng)。因(yin)此，電(dian)(dian)(dian)池內(nei)部正常(chang)(chang)的(de)(de)電(dian)(dian)(dian)荷傳(chuan)遞和物質傳(chuan)遞過程(cheng)(cheng)是保證正常(chang)(chang)輸(shu)出電(dian)(dian)(dian)能的(de)(de)必(bi)要條件。充(chong)電(dian)(dian)(dian)時，電(dian)(dian)(dian)池內(nei)部的(de)(de)傳(chuan)電(dian)(dian)(dian)和傳(chuan)質過程(cheng)(cheng)的(de)(de)方向恰與放電(dian)(dian)(dian)相反；電(dian)(dian)(dian)極反應必(bi)須是可(ke)逆的(de)(de)，才(cai)能保證反方向傳(chuan)質與傳(chuan)電(dian)(dian)(dian)過程(cheng)(cheng)的(de)(de)正常(chang)(chang)進行。

因(yin)此，電(dian)極反(fan)應(ying)可逆是構(gou)成(cheng)蓄電(dian)池的必要條件。為吉布斯反(fan)應(ying)自由能增量(焦)；F為法(fa)拉第常(chang)數(shu)=96500庫=26.8安·小時；n為(wei)電(dian)(dian)(dian)(dian)(dian)池(chi)反應的(de)(de)當量數。這(zhe)是電(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)動勢與電(dian)(dian)(dian)(dian)(dian)池(chi)反應之間(jian)的(de)(de)基本熱(re)力學關(guan)系式，也(ye)是計算電(dian)(dian)(dian)(dian)(dian)池(chi)能(neng)量轉換效率的(de)(de)基本熱(re)力學方程式。實際上(shang)，當電(dian)(dian)(dian)(dian)(dian)流流過(guo)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)時，電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)電(dian)(dian)(dian)(dian)(dian)勢都(dou)要(yao)偏(pian)離熱(re)力學平衡(heng)的(de)(de)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)電(dian)(dian)(dian)(dian)(dian)勢，這(zhe)種(zhong)現象(xiang)(xiang)稱(cheng)為(wei)極(ji)(ji)(ji)(ji)化(hua)(hua)(hua)(hua)。電(dian)(dian)(dian)(dian)(dian)流密度(du)(du)（單位電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)面(mian)(mian)積上(shang)通過(guo)的(de)(de)電(dian)(dian)(dian)(dian)(dian)流）越(yue)大(da)(da)，極(ji)(ji)(ji)(ji)化(hua)(hua)(hua)(hua)越(yue)嚴(yan)重。極(ji)(ji)(ji)(ji)化(hua)(hua)(hua)(hua)現象(xiang)(xiang)是造(zao)成電(dian)(dian)(dian)(dian)(dian)池(chi)能(neng)量損失(shi)的(de)(de)重要(yao)原(yuan)因之一。極(ji)(ji)(ji)(ji)化(hua)(hua)(hua)(hua)的(de)(de)原(yuan)因有三：①由電(dian)(dian)(dian)(dian)(dian)池(chi)中(zhong)各部分(fen)電(dian)(dian)(dian)(dian)(dian)阻造(zao)成的(de)(de)極(ji)(ji)(ji)(ji)化(hua)(hua)(hua)(hua)稱(cheng)為(wei)歐姆極(ji)(ji)(ji)(ji)化(hua)(hua)(hua)(hua)；②由電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)－電(dian)(dian)(dian)(dian)(dian)解質界面(mian)(mian)層中(zhong)電(dian)(dian)(dian)(dian)(dian)荷傳(chuan)遞(di)過(guo)程的(de)(de)阻滯(zhi)造(zao)成的(de)(de)極(ji)(ji)(ji)(ji)化(hua)(hua)(hua)(hua)稱(cheng)為(wei)活(huo)化(hua)(hua)(hua)(hua)極(ji)(ji)(ji)(ji)化(hua)(hua)(hua)(hua)；③由電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)－電(dian)(dian)(dian)(dian)(dian)解質界面(mian)(mian)層中(zhong)傳(chuan)質過(guo)程遲緩而造(zao)成的(de)(de)極(ji)(ji)(ji)(ji)化(hua)(hua)(hua)(hua)稱(cheng)為(wei)濃差(cha)極(ji)(ji)(ji)(ji)化(hua)(hua)(hua)(hua)。減(jian)(jian)小(xiao)極(ji)(ji)(ji)(ji)化(hua)(hua)(hua)(hua)的(de)(de)方法是增(zeng)大(da)(da)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)反應面(mian)(mian)積、減(jian)(jian)小(xiao)電(dian)(dian)(dian)(dian)(dian)流密度(du)(du)、提高反應溫度(du)(du)以及改善電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)表面(mian)(mian)的(de)(de)催化(hua)(hua)(hua)(hua)活(huo)性。

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薄膜太陽能電池優缺點

薄膜型太陽能電池由于使用材料較少，就每一模塊的成本而言比起堆積型太陽能電池有(you)著明顯的減少，制造程序上所需的能量也(ye)較(jiao)堆(dui)積(ji)型太(tai)陽能電池來的小，它同時也(ye)擁有(you)整合型式的連接模(mo)塊，如此(ci)一來便可省下了獨立模(mo)塊所需在(zai)固定和內部連接的成本。

未來薄膜型太陽能電池將可能會取代現今一般常用硅太陽能電池，而成為市場主流。非晶硅太陽能電池與單晶硅太陽能電池或多晶硅太陽能電池的最主要差異是材料的不同，單晶硅太陽能電池或多晶硅太陽能電池的材料都疏，而非晶硅太陽能電池的材料則是SiH4，因為材料(liao)的不同而使非晶硅(gui)(gui)太陽(yang)能電池(chi)的構造與晶硅(gui)(gui)太陽(yang)能電池(chi)稍有不同。

SiH4最(zui)大(da)的優點為吸光效果及光導效果都很好，但其電氣特性類似絕緣體(ti)，與(yu)硅的半(ban)導體(ti)特性相差甚遠，因(yin)此最(zui)初認為SiH4是不(bu)適合(he)的(de)材料。但在1970年代(dai)科學家克服(fu)了這個(ge)問題，不久(jiu)后美國的RCA制(zhi)造出第一個非晶硅太(tai)陽能電池。雖然SiH4吸(xi)光(guang)效(xiao)果及(ji)光(guang)導效(xiao)果都很(hen)好，但由(you)(you)于(yu)其結晶構造比(bi)多晶硅太陽能電(dian)(dian)池差，所以懸浮鍵的問(wen)題(ti)比(bi)多晶硅太陽能電(dian)(dian)池還嚴(yan)重，自由(you)(you)電(dian)(dian)子與電(dian)(dian)洞復(fu)合的速率非常快；此(ci)外SiH4的結晶構造不(bu)規則會阻礙(ai)電(dian)子與電(dian)洞(dong)的移動使得(de)擴散范圍變短(duan)。

基于以上兩個因素，因此當光(guang)照射在SiH4上(shang)產(chan)生電子電洞(dong)對后，必須(xu)盡快將(jiang)電子與電洞(dong)分(fen)離，才(cai)能有效產(chan)生光電效應。所以非晶硅太(tai)陽能電池大多做得(de)很薄(bo)，以減少自由電子與電洞(dong)復合。由于(yu)SiH4的(de)(de)吸光效(xiao)果很好(hao)，雖然(ran)非晶硅太陽(yang)能電(dian)池做得(de)很薄，仍然(ran)可以吸收(shou)大部分的(de)(de)光。

非晶硅太陽(yang)能(neng)電(dian)池最(zui)大的優點為成本(ben)低(di)，而缺(que)點則(ze)是效率低(di)及(ji)光(guang)電(dian)轉換(huan)效率隨使用時(shi)間衰退(tui)的問題(ti)。因此非晶硅太陽(yang)能(neng)電(dian)池在小電(dian)力市場(chang)上被廣泛使用，但(dan)在發電(dian)市場(chang)上則(ze)較不(bu)具競爭(zheng)力。