本研究主要探討鐵電材料的光伏打特性，鐵電光伏打效應不同於半導體的光伏打效應，是由鐵電材料自發極化造成內建偏壓，並以此分離由材料照光而產生的電子-電洞對，進而提取出電流，效應與半導體的p-n接面不同。實驗分為兩部分，第一部分是利用固相反應法合成摻雜錳的鈦酸鉍鈉多晶塊材(Bi0.5Na0.5TiO3：Mn)，藉由摻雜改善傳統鐵電材料導電不佳的問題，並觀察其極化後的光伏性質。第二部分則是試圖合成一種鮮少被探討的極性材料-鈣鐵硫氧(CaFeSO)，根據近期理論模擬結果，認為此材料由於特殊的結構與光學特性，使其具有不錯的光伏應用潛力，因而本實驗企圖合成此化合物，並驗證模擬結果。
無摻雜的鈦酸鉍鈉於1100°C的燒結溫度下持溫2小時可獲得純相，摻雜錳的鈦酸鉍鈉則於1000°C的燒結溫度下持溫2小時可獲得純相，摻雜錳的鈦酸鉍鈉相較於無摻雜者，電阻率約降低兩個數量級。將不同的試片依其條件施加電壓，於室溫下進行極化，對於各成分選取d33值最大者量測照光與隔絕光源條件下的電流-電壓特性。實驗顯示照光後所有的試片皆有光電流的產生，且隨著摻雜量增加，產生的光電流也愈大，並以摻雜5%的錳其開路電壓最大，約為0.34V。此外以摻雜3%的錳其光電流增幅最多，無摻雜時的變化最小，但所有試片皆未表現出如同p-n二極體的I-V特性曲線。儘管以不同的起始物搭配各種燒結條件，調控溫度和時間，CaFeSO並未成功於本實驗中合成，卻合成出含有單一四元硫氧化合物的樣品，分別為Ca2Fe2S2O3與Ca3Fe4S3O6，藉由變溫電阻與席貝克係數的分析，顯示前者為p型半導體，後者為n型半導體，且兩者在照光後皆無光電流的產生。

The aim of this work was to search for novel ferroelectric photovoltaic materials. The ferroelectric materials studied in this work were Bi0.5Na0.5TiO3 and CaFeSO because they haven’t been investigated thoroughly for the applications of interest. Owing to a lack of carrier concentration, ferroelectric materials usually have a very low conductivity below 10-8 S/cm which constrains the output power of ferroelectric photovoltaics. In this study, in order to increase the carrier concentration, Bi0.5Na0.5TiO3 was doped with maganese ion. Polycrystalline samples of Bi0.5Na0.5TiO3:Mn were prepared using the solid-state reaction method. X-ray diffraction showed that pure phases of undoped and Mn doped Bi0.5Na0.5TiO3 could be obtained after sintering at 1100°C and 1000°C for 2 hours respectively. The conductivity of Bi0.5Na0.5TiO3:5%Mn increased by two 2 orders of magnitude as compared with the undoped Bi0.5Na0.5TiO3. After poling, the current-voltage curves of the samples were measured with and without light irradiation. There was only a slight change in the output current before and after illumination for the undoped sample, indicating a lack of photoexcited carriers. However, the output current increased with increases in the Mn content. CaFeSO was not successfully synthesized using the solid-state reaction in this work; nevertheless, two other compounds in this family, Ca2Fe2S2O3 and Ca3Fe4S3O6, could be obtained by solid-state reaction under different conditions. The measurement of resistivity and the Seebeck coefficient indicated that Ca2Fe2S2O3 is a p-type semiconductor and that Ca3Fe4S3O6 is an n-type semiconductor. Neither Ca2Fe2S2O3 nor Ca3Fe4S3O6 produced photocurrent after illumination, which was possibly due to an overly high recombination rate.

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