薄膜太陽能電池原理

在化(hua)(hua)學(xue)電(dian)(dian)池(chi)中(zhong)，化(hua)(hua)學(xue)能直接轉(zhuan)變為電(dian)(dian)能是靠電(dian)(dian)池(chi)內部自發進行氧(yang)(yang)化(hua)(hua)、還(huan)原等(deng)化(hua)(hua)學(xue)反(fan)(fan)應的結(jie)果，這種反(fan)(fan)應分別在兩個(ge)電(dian)(dian)極(ji)上進行。負極(ji)活性物(wu)質由電(dian)(dian)位(wei)較負并在電(dian)(dian)解(jie)質中(zhong)穩定的還(huan)原劑組(zu)成，如(ru)(ru)鋅(xin)、鎘、鉛等(deng)活潑金屬和氫(qing)或碳(tan)氫(qing)化(hua)(hua)合物(wu)等(deng)。正極(ji)活性物(wu)質由電(dian)(dian)位(wei)較正并在電(dian)(dian)解(jie)質中(zhong)穩定的氧(yang)(yang)化(hua)(hua)劑組(zu)成，如(ru)(ru)二(er)氧(yang)(yang)化(hua)(hua)錳、二(er)氧(yang)(yang)化(hua)(hua)鉛、氧(yang)(yang)化(hua)(hua)鎳等(deng)金屬氧(yang)(yang)化(hua)(hua)物(wu)，氧(yang)(yang)或空氣(qi)，鹵素及其鹽類，含氧(yang)(yang)酸及其鹽類等(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(dian)壓)，但沒(mei)有電流，存儲在(zai)電池中(zhong)的(de)化(hua)學能并不轉換為電能。當外電路閉合時，在(zai)兩電極(ji)電位差的(de)作(zuo)用下(xia)即(ji)有電流流過外電路。

同時在電(dian)池內部(bu)，由于電(dian)解質(zhi)中不存(cun)在自由電(dian)子，電(dian)荷的傳遞必然伴隨(sui)兩極活性物質(zhi)與(yu)電(dian)解質(zhi)界(jie)面的氧(yang)化(hua)或還原反應，以及反應物和反應產(chan)物的物質(zhi)遷移。電(dian)(dian)荷在電(dian)(dian)解質(zhi)(zhi)中(zhong)的(de)傳(chuan)(chuan)(chuan)遞(di)也(ye)要(yao)由(you)離子的(de)遷移來完成。因此，電(dian)(dian)池內部正常的(de)電(dian)(dian)荷傳(chuan)(chuan)(chuan)遞(di)和物(wu)質(zhi)(zhi)傳(chuan)(chuan)(chuan)遞(di)過程是保(bao)證正常輸出電(dian)(dian)能(neng)的(de)必(bi)要(yao)條(tiao)件(jian)。充電(dian)(dian)時，電(dian)(dian)池內部的(de)傳(chuan)(chuan)(chuan)電(dian)(dian)和傳(chuan)(chuan)(chuan)質(zhi)(zhi)過程的(de)方向(xiang)恰與放電(dian)(dian)相反；電(dian)(dian)極反應必(bi)須(xu)是可逆的(de)，才(cai)能(neng)保(bao)證反方向(xiang)傳(chuan)(chuan)(chuan)質(zhi)(zhi)與傳(chuan)(chuan)(chuan)電(dian)(dian)過程的(de)正常進行。

因此，電極(ji)反(fan)應(ying)可逆(ni)是構成蓄電池的(de)必要條件。為吉(ji)布斯(si)反(fan)應(ying)自由能增量(焦(jiao))；F為(wei)法拉第(di)常數=96500庫=26.8安·小時；n為(wei)(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池反應(ying)(ying)的(de)(de)當(dang)(dang)量(liang)數。這(zhe)是(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)(dian)動勢與電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池反應(ying)(ying)之(zhi)間的(de)(de)基本(ben)熱(re)力學(xue)關系(xi)式，也(ye)是(shi)計算電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池能量(liang)轉換效率(lv)的(de)(de)基本(ben)熱(re)力學(xue)方程式。實際上，當(dang)(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)流(liu)過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)時，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)勢都要(yao)偏(pian)離熱(re)力學(xue)平衡的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)勢，這(zhe)種現象稱為(wei)(wei)極(ji)(ji)化(hua)(hua)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)密度(du)（單位電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)面(mian)(mian)(mian)積上通過(guo)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)）越(yue)大(da)，極(ji)(ji)化(hua)(hua)越(yue)嚴重(zhong)。極(ji)(ji)化(hua)(hua)現象是(shi)造(zao)(zao)成電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池能量(liang)損失的(de)(de)重(zhong)要(yao)原因之(zhi)一。極(ji)(ji)化(hua)(hua)的(de)(de)原因有三(san)：①由電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池中(zhong)各部分(fen)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻造(zao)(zao)成的(de)(de)極(ji)(ji)化(hua)(hua)稱為(wei)(wei)歐姆極(ji)(ji)化(hua)(hua)；②由電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)－電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)質(zhi)(zhi)界面(mian)(mian)(mian)層中(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷傳(chuan)遞(di)過(guo)程的(de)(de)阻滯造(zao)(zao)成的(de)(de)極(ji)(ji)化(hua)(hua)稱為(wei)(wei)活(huo)化(hua)(hua)極(ji)(ji)化(hua)(hua)；③由電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)－電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)質(zhi)(zhi)界面(mian)(mian)(mian)層中(zhong)傳(chuan)質(zhi)(zhi)過(guo)程遲緩而(er)造(zao)(zao)成的(de)(de)極(ji)(ji)化(hua)(hua)稱為(wei)(wei)濃差極(ji)(ji)化(hua)(hua)。減小極(ji)(ji)化(hua)(hua)的(de)(de)方法是(shi)增大(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)反應(ying)(ying)面(mian)(mian)(mian)積、減小電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)密度(du)、提高反應(ying)(ying)溫(wen)度(du)以(yi)及改善電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)表(biao)面(mian)(mian)(mian)的(de)(de)催(cui)化(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著(zhu)明(ming)顯的(de)(de)減少，制造程序上所(suo)(suo)需(xu)的(de)(de)能量也(ye)較堆(dui)積(ji)型(xing)(xing)太陽能電池(chi)來的(de)(de)小，它同時也(ye)擁有整合(he)型(xing)(xing)式的(de)(de)連(lian)接(jie)(jie)模塊(kuai)，如此一來便(bian)可省下了獨(du)立模塊(kuai)所(suo)(suo)需(xu)在固定和內(nei)部(bu)連(lian)接(jie)(jie)的(de)(de)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(tong)而使非晶(jing)硅太陽能電池(chi)的構造與(yu)晶(jing)硅太陽能電池(chi)稍有(you)不同(tong)。

SiH4最大的優點(dian)為吸光效果及光導效果都很好，但其(qi)電氣特(te)(te)性類似絕緣體，與(yu)硅的半(ban)導體特(te)(te)性相差甚遠，因此最初認為SiH4是(shi)不適(shi)合的材料。但(dan)在1970年代科(ke)學家(jia)克(ke)服了這個問題，不久后美國的RCA制造(zao)出(chu)第一個非(fei)晶硅太陽能電池。雖然SiH4吸光(guang)效果(guo)及光(guang)導效果(guo)都很好，但由于其結晶構造比(bi)(bi)多晶硅太陽能(neng)電(dian)池(chi)差，所以(yi)懸(xuan)浮(fu)鍵的問(wen)題比(bi)(bi)多晶硅太陽能(neng)電(dian)池(chi)還(huan)嚴重，自由電(dian)子與電(dian)洞復(fu)合的速(su)率(lv)非常(chang)快(kuai)；此(ci)外SiH4的結晶構造不(bu)規(gui)則會阻礙電(dian)(dian)子(zi)與電(dian)(dian)洞的移動(dong)使得擴散范圍(wei)變短。

基于以(yi)上(shang)兩個因(yin)素，因(yin)此(ci)當光(guang)照射(she)在SiH4上產(chan)(chan)生電(dian)(dian)子電(dian)(dian)洞對后(hou)，必須盡快(kuai)將電(dian)(dian)子與電(dian)(dian)洞分離，才能有(you)效產(chan)(chan)生光電(dian)(dian)效應。所以非晶(jing)硅太陽(yang)能電(dian)(dian)池大多(duo)做得很薄，以減少自由電(dian)(dian)子與電(dian)(dian)洞復合(he)。由于SiH4的(de)吸(xi)光(guang)效果很(hen)好，雖然非晶硅太陽能電池做(zuo)得很(hen)薄，仍然可(ke)以吸(xi)收大部分(fen)的(de)光(guang)。

非(fei)晶硅太陽(yang)能(neng)電(dian)池(chi)最大的(de)優(you)點(dian)為成本低，而缺點(dian)則(ze)是效率(lv)低及(ji)光電(dian)轉換效率(lv)隨使用時間衰(shuai)退的(de)問題。因此非(fei)晶硅太陽(yang)能(neng)電(dian)池(chi)在(zai)(zai)小電(dian)力市場(chang)上(shang)被廣泛使用，但在(zai)(zai)發電(dian)市場(chang)上(shang)則(ze)較不具競爭力。