薄膜太陽能電池原理

在(zai)化(hua)(hua)學電(dian)(dian)(dian)(dian)池中，化(hua)(hua)學能(neng)直(zhi)接轉(zhuan)變為電(dian)(dian)(dian)(dian)能(neng)是靠電(dian)(dian)(dian)(dian)池內部自(zi)發進行(xing)氧(yang)(yang)化(hua)(hua)、還(huan)原等(deng)化(hua)(hua)學反應的結(jie)果，這種反應分別在(zai)兩個電(dian)(dian)(dian)(dian)極(ji)(ji)上進行(xing)。負(fu)極(ji)(ji)活(huo)(huo)性物(wu)質(zhi)(zhi)由電(dian)(dian)(dian)(dian)位(wei)較負(fu)并在(zai)電(dian)(dian)(dian)(dian)解質(zhi)(zhi)中穩定(ding)的還(huan)原劑組(zu)成，如鋅、鎘(ge)、鉛等(deng)活(huo)(huo)潑金屬和氫或碳氫化(hua)(hua)合物(wu)等(deng)。正極(ji)(ji)活(huo)(huo)性物(wu)質(zhi)(zhi)由電(dian)(dian)(dian)(dian)位(wei)較正并在(zai)電(dian)(dian)(dian)(dian)解質(zhi)(zhi)中穩定(ding)的氧(yang)(yang)化(hua)(hua)劑組(zu)成，如二(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(kong)氣，鹵素及其鹽類，含(han)氧(yang)(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(kai)路電(dian)壓)，但沒有電(dian)(dian)流，存(cun)儲在電(dian)(dian)池中的化學能并不(bu)轉換為電(dian)(dian)能。當外(wai)電(dian)(dian)路閉合時，在兩電(dian)(dian)極電(dian)(dian)位差(cha)的作用下即有電(dian)(dian)流流過外(wai)電(dian)(dian)路。

同時(shi)在電(dian)(dian)池內部，由于電(dian)(dian)解(jie)質(zhi)(zhi)中不(bu)存(cun)在自由電(dian)(dian)子，電(dian)(dian)荷的傳遞必然伴隨兩極(ji)活(huo)性物(wu)質(zhi)(zhi)與電(dian)(dian)解(jie)質(zhi)(zhi)界面的氧化(hua)或還原(yuan)反應，以及(ji)反應物(wu)和反應產物(wu)的物(wu)質(zhi)(zhi)遷移(yi)。電(dian)(dian)(dian)(dian)荷在電(dian)(dian)(dian)(dian)解(jie)質(zhi)(zhi)中的(de)(de)傳(chuan)(chuan)遞(di)(di)也要由離子的(de)(de)遷移來完(wan)成。因此，電(dian)(dian)(dian)(dian)池內部(bu)(bu)正常(chang)的(de)(de)電(dian)(dian)(dian)(dian)荷傳(chuan)(chuan)遞(di)(di)和(he)物質(zhi)(zhi)傳(chuan)(chuan)遞(di)(di)過(guo)程(cheng)是(shi)(shi)保(bao)證正常(chang)輸出電(dian)(dian)(dian)(dian)能(neng)的(de)(de)必要條件。充電(dian)(dian)(dian)(dian)時(shi)，電(dian)(dian)(dian)(dian)池內部(bu)(bu)的(de)(de)傳(chuan)(chuan)電(dian)(dian)(dian)(dian)和(he)傳(chuan)(chuan)質(zhi)(zhi)過(guo)程(cheng)的(de)(de)方向恰與(yu)放電(dian)(dian)(dian)(dian)相反(fan)；電(dian)(dian)(dian)(dian)極反(fan)應必須是(shi)(shi)可(ke)逆的(de)(de)，才能(neng)保(bao)證反(fan)方向傳(chuan)(chuan)質(zhi)(zhi)與(yu)傳(chuan)(chuan)電(dian)(dian)(dian)(dian)過(guo)程(cheng)的(de)(de)正常(chang)進行。

因此(ci)，電(dian)極反應可(ke)逆是構成蓄電(dian)池的(de)必要(yao)條件。為吉布斯反應自由能增量(焦)；F為法(fa)拉第(di)常數=96500庫=26.8安·小時；n為(wei)(wei)(wei)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)反應(ying)的(de)當(dang)量(liang)數。這是(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)動勢(shi)與電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)反應(ying)之間的(de)基(ji)(ji)本熱(re)(re)力學(xue)關系式，也是(shi)(shi)(shi)計(ji)算電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)能量(liang)轉換效率的(de)基(ji)(ji)本熱(re)(re)力學(xue)方程(cheng)(cheng)式。實際上(shang)，當(dang)電(dian)(dian)(dian)(dian)(dian)流流過(guo)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)時，電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)勢(shi)都要偏離熱(re)(re)力學(xue)平衡的(de)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)勢(shi)，這種(zhong)現象(xiang)稱為(wei)(wei)(wei)極(ji)(ji)化(hua)(hua)。電(dian)(dian)(dian)(dian)(dian)流密(mi)度（單位(wei)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)面(mian)積(ji)上(shang)通過(guo)的(de)電(dian)(dian)(dian)(dian)(dian)流）越(yue)大，極(ji)(ji)化(hua)(hua)越(yue)嚴重。極(ji)(ji)化(hua)(hua)現象(xiang)是(shi)(shi)(shi)造成電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)能量(liang)損失的(de)重要原因之一(yi)。極(ji)(ji)化(hua)(hua)的(de)原因有三：①由(you)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)中(zhong)(zhong)各部分電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)造成的(de)極(ji)(ji)化(hua)(hua)稱為(wei)(wei)(wei)歐姆極(ji)(ji)化(hua)(hua)；②由(you)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)－電(dian)(dian)(dian)(dian)(dian)解(jie)質(zhi)界面(mian)層中(zhong)(zhong)電(dian)(dian)(dian)(dian)(dian)荷傳(chuan)遞(di)過(guo)程(cheng)(cheng)的(de)阻(zu)(zu)滯(zhi)造成的(de)極(ji)(ji)化(hua)(hua)稱為(wei)(wei)(wei)活化(hua)(hua)極(ji)(ji)化(hua)(hua)；③由(you)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)－電(dian)(dian)(dian)(dian)(dian)解(jie)質(zhi)界面(mian)層中(zhong)(zhong)傳(chuan)質(zhi)過(guo)程(cheng)(cheng)遲緩而造成的(de)極(ji)(ji)化(hua)(hua)稱為(wei)(wei)(wei)濃差極(ji)(ji)化(hua)(hua)。減(jian)小(xiao)極(ji)(ji)化(hua)(hua)的(de)方法是(shi)(shi)(shi)增大電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)反應(ying)面(mian)積(ji)、減(jian)小(xiao)電(dian)(dian)(dian)(dian)(dian)流密(mi)度、提高反應(ying)溫度以及改善電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)表面(mian)的(de)催化(hua)(hua)活性。

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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明顯的(de)減(jian)少，制(zhi)造程序上所(suo)需的(de)能量(liang)也較堆(dui)積型太陽能電池來的(de)小，它(ta)同時也擁有整合型式的(de)連(lian)接(jie)(jie)模(mo)塊(kuai)，如此一來便可省下了(le)獨立(li)模(mo)塊(kuai)所(suo)需在固定和(he)內部(bu)連(lian)接(jie)(jie)的(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，因為材料的不(bu)同(tong)而使非(fei)晶硅太陽(yang)能(neng)電池(chi)的構造與晶硅太陽(yang)能(neng)電池(chi)稍(shao)有不(bu)同(tong)。

SiH4最大的優點為吸光效果及(ji)光導效果都很好，但其電氣特(te)性類似絕緣體，與(yu)硅的半導體特(te)性相差(cha)甚遠，因此最初認為SiH4是不適合的材料。但在(zai)1970年代科學家(jia)克服了(le)這個問題，不(bu)久后美(mei)國的RCA制造(zao)出第一個非晶硅太陽能(neng)電池。雖然SiH4吸光效果及光導效果都很好，但由于其結晶構造比(bi)多晶硅(gui)太陽能(neng)電池(chi)差，所以懸(xuan)浮鍵的問(wen)題比(bi)多晶硅(gui)太陽能(neng)電池(chi)還嚴重，自由電子(zi)與電洞復合的速(su)率非常快(kuai)；此外SiH4的(de)結晶構(gou)造不規則會阻(zu)礙電子與電洞(dong)的(de)移動(dong)使得(de)擴散范圍變(bian)短(duan)。

基于以上兩個因素，因此當(dang)光照射在SiH4上產生電(dian)(dian)(dian)子電(dian)(dian)(dian)洞對后，必須盡(jin)快將電(dian)(dian)(dian)子與(yu)電(dian)(dian)(dian)洞分離，才能(neng)有(you)效(xiao)產生光(guang)電(dian)(dian)(dian)效(xiao)應。所以(yi)非晶硅太陽能(neng)電(dian)(dian)(dian)池大多做(zuo)得很(hen)薄，以(yi)減少(shao)自由電(dian)(dian)(dian)子與(yu)電(dian)(dian)(dian)洞復(fu)合。由于SiH4的吸光效果很(hen)好，雖然(ran)非(fei)晶硅太陽能電池做得很(hen)薄，仍然(ran)可以吸收大部分(fen)的光。

非晶(jing)硅太(tai)陽能(neng)電(dian)池(chi)最(zui)大的優(you)點為成本低，而缺點則(ze)是效(xiao)率(lv)(lv)低及光電(dian)轉換(huan)效(xiao)率(lv)(lv)隨使用(yong)時間衰(shuai)退的問題。因此非晶(jing)硅太(tai)陽能(neng)電(dian)池(chi)在小(xiao)電(dian)力市(shi)場(chang)上(shang)被廣泛使用(yong)，但在發電(dian)市(shi)場(chang)上(shang)則(ze)較(jiao)不具競(jing)爭力。