薄膜太陽能電池原理

在化(hua)學電池中(zhong)，化(hua)學能直接(jie)轉變為(wei)電能是靠(kao)電池內部自發進行(xing)氧(yang)化(hua)、還原等(deng)化(hua)學反應(ying)的(de)結果，這種反應(ying)分(fen)別(bie)在兩個電極上進行(xing)。負極活(huo)性物質由電位(wei)(wei)較負并在電解質中(zhong)穩定的(de)還原劑組(zu)成，如(ru)鋅、鎘、鉛等(deng)活(huo)潑(po)金屬和氫(qing)或碳氫(qing)化(hua)合物等(deng)。正(zheng)極活(huo)性物質由電位(wei)(wei)較正(zheng)并在電解質中(zhong)穩定的(de)氧(yang)化(hua)劑組(zu)成，如(ru)二氧(yang)化(hua)錳、二氧(yang)化(hua)鉛、氧(yang)化(hua)鎳等(deng)金屬氧(yang)化(hua)物，氧(yang)或空氣，鹵(lu)素及(ji)其(qi)鹽類，含氧(yang)酸及(ji)其(qi)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(開路電壓)，但沒(mei)有電(dian)流(liu)(liu)(liu)，存儲在電(dian)池中(zhong)的化(hua)學(xue)能并(bing)不轉換為電(dian)能。當外(wai)(wai)電(dian)路閉合時，在兩電(dian)極電(dian)位差的作(zuo)用(yong)下即有電(dian)流(liu)(liu)(liu)流(liu)(liu)(liu)過外(wai)(wai)電(dian)路。

同時在(zai)電池內部(bu)，由于電解質中(zhong)不(bu)存在(zai)自由電子，電荷(he)的(de)傳遞必然伴隨兩極活性物質與電解質界(jie)面的(de)氧化或還(huan)原反應，以(yi)及反應物和反應產(chan)物的(de)物質遷移。電(dian)(dian)(dian)荷在(zai)電(dian)(dian)(dian)解質(zhi)中(zhong)的(de)(de)傳(chuan)(chuan)(chuan)(chuan)遞也要(yao)由離子的(de)(de)遷(qian)移來完成。因此(ci)，電(dian)(dian)(dian)池內部(bu)正常的(de)(de)電(dian)(dian)(dian)荷傳(chuan)(chuan)(chuan)(chuan)遞和物(wu)質(zhi)傳(chuan)(chuan)(chuan)(chuan)遞過程是保證(zheng)正常輸出電(dian)(dian)(dian)能的(de)(de)必(bi)要(yao)條件。充電(dian)(dian)(dian)時，電(dian)(dian)(dian)池內部(bu)的(de)(de)傳(chuan)(chuan)(chuan)(chuan)電(dian)(dian)(dian)和傳(chuan)(chuan)(chuan)(chuan)質(zhi)過程的(de)(de)方(fang)向恰(qia)與放電(dian)(dian)(dian)相反；電(dian)(dian)(dian)極(ji)反應必(bi)須(xu)是可逆的(de)(de)，才能保證(zheng)反方(fang)向傳(chuan)(chuan)(chuan)(chuan)質(zhi)與傳(chuan)(chuan)(chuan)(chuan)電(dian)(dian)(dian)過程的(de)(de)正常進行。

因此，電極反應可逆是構(gou)成蓄電池的必要(yao)條件(jian)。為(wei)吉布斯反應自(zi)由能增量(焦(jiao))；F為法拉第常(chang)數(shu)=96500庫=26.8安·小時(shi)；n為(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池反(fan)應的(de)(de)(de)(de)(de)當量(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(fan)應之間的(de)(de)(de)(de)(de)基(ji)本熱(re)力學(xue)關系式，也是(shi)計(ji)算電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池能(neng)量(liang)轉換效率的(de)(de)(de)(de)(de)基(ji)本熱(re)力學(xue)方程式。實際上(shang)，當電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)流(liu)過電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)時，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)勢都要偏離熱(re)力學(xue)平衡的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)勢，這(zhe)種現象(xiang)稱(cheng)為(wei)極(ji)化(hua)(hua)(hua)(hua)(hua)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)密度(du)（單位(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)面積上(shang)通過的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)）越(yue)大，極(ji)化(hua)(hua)(hua)(hua)(hua)越(yue)嚴(yan)重(zhong)。極(ji)化(hua)(hua)(hua)(hua)(hua)現象(xiang)是(shi)造(zao)(zao)成(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池能(neng)量(liang)損失的(de)(de)(de)(de)(de)重(zhong)要原因(yin)之一。極(ji)化(hua)(hua)(hua)(hua)(hua)的(de)(de)(de)(de)(de)原因(yin)有三：①由電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池中(zhong)(zhong)各(ge)部分電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻造(zao)(zao)成(cheng)(cheng)的(de)(de)(de)(de)(de)極(ji)化(hua)(hua)(hua)(hua)(hua)稱(cheng)為(wei)歐姆極(ji)化(hua)(hua)(hua)(hua)(hua)；②由電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)－電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)(jie)質界面層中(zhong)(zhong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)傳遞過程的(de)(de)(de)(de)(de)阻滯造(zao)(zao)成(cheng)(cheng)的(de)(de)(de)(de)(de)極(ji)化(hua)(hua)(hua)(hua)(hua)稱(cheng)為(wei)活(huo)化(hua)(hua)(hua)(hua)(hua)極(ji)化(hua)(hua)(hua)(hua)(hua)；③由電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)－電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)(jie)質界面層中(zhong)(zhong)傳質過程遲緩(huan)而造(zao)(zao)成(cheng)(cheng)的(de)(de)(de)(de)(de)極(ji)化(hua)(hua)(hua)(hua)(hua)稱(cheng)為(wei)濃差極(ji)化(hua)(hua)(hua)(hua)(hua)。減(jian)小(xiao)極(ji)化(hua)(hua)(hua)(hua)(hua)的(de)(de)(de)(de)(de)方法是(shi)增(zeng)大電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)反(fan)應面積、減(jian)小(xiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)密度(du)、提(ti)高反(fan)應溫度(du)以及改善電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)表面的(de)(de)(de)(de)(de)催(cui)化(hua)(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著(zhu)明(ming)顯的(de)(de)減少，制(zhi)造程序上所(suo)需的(de)(de)能(neng)(neng)量(liang)也較堆積型太陽能(neng)(neng)電池來(lai)的(de)(de)小，它同時也擁有整合型式的(de)(de)連(lian)接模塊(kuai)，如(ru)此一來(lai)便可(ke)省下了獨立模塊(kuai)所(suo)需在(zai)固定(ding)和內(nei)部(bu)連(lian)接的(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(cai)料的不(bu)同(tong)而使非晶(jing)硅太陽能電池(chi)的構造與晶(jing)硅太陽能電池(chi)稍有不(bu)同(tong)。

SiH4最大的優點為吸光(guang)效(xiao)果及光(guang)導效(xiao)果都很(hen)好，但其電氣特性類似(si)絕緣體(ti)，與硅(gui)的半(ban)導體(ti)特性相差甚遠(yuan)，因此最初認為SiH4是不(bu)適合的材料。但在1970年代科學家克服(fu)了這個問(wen)題(ti)，不(bu)久后美國的RCA制造出第(di)一個(ge)非晶硅(gui)太陽能電(dian)池。雖然SiH4吸光(guang)效(xiao)果及(ji)光(guang)導(dao)效(xiao)果都很好，但由于其結晶(jing)構造比(bi)多晶(jing)硅太(tai)陽能電(dian)(dian)池差，所以懸(xuan)浮鍵的問(wen)題比(bi)多晶(jing)硅太(tai)陽能電(dian)(dian)池還嚴重，自由電(dian)(dian)子(zi)與電(dian)(dian)洞復合的速率非常(chang)快；此外SiH4的結晶(jing)構造(zao)不規則會阻礙電(dian)子(zi)與電(dian)洞的移(yi)動(dong)使得(de)擴散(san)范圍(wei)變短。

基于以上兩個(ge)因素，因此當(dang)光照射在SiH4上產(chan)生電(dian)子電(dian)洞(dong)對后，必(bi)須盡快將電(dian)子與電(dian)洞(dong)分離(li)，才能(neng)有效產(chan)生光電(dian)效應。所(suo)以非晶硅太(tai)陽能(neng)電(dian)池大多做(zuo)得很薄，以減少自由電(dian)子與電(dian)洞(dong)復(fu)合(he)。由于SiH4的(de)吸光(guang)效果很好，雖然(ran)非晶硅太陽能(neng)電池做得很薄，仍然(ran)可以吸收大部分的(de)光(guang)。

非晶(jing)硅太陽能電(dian)(dian)(dian)池最(zui)大的(de)優(you)點為成(cheng)本(ben)低，而(er)缺(que)點則是(shi)效(xiao)率低及光電(dian)(dian)(dian)轉換效(xiao)率隨使用(yong)時間衰(shuai)退的(de)問題。因此非晶(jing)硅太陽能電(dian)(dian)(dian)池在小電(dian)(dian)(dian)力(li)(li)市場(chang)(chang)上被廣泛(fan)使用(yong)，但在發電(dian)(dian)(dian)市場(chang)(chang)上則較不具(ju)競爭力(li)(li)。