利用飛秒激發探測光譜研究銅銦鎵硒太陽能電池其奈米柱陣列結構之超快載子動力學

Abstract

本論文利用準分子脈衝雷射蒸鍍法製備銅銦鎵硒(CIGS)薄膜，接著使用離子研磨機在CIGS薄膜表面蝕刻出奈米柱陣列(nano-tip arrays, NTRs)結構。在掃描式電子顯微鏡圖中可以觀察到在CIGS NTRs二次相Cu2-xSe附近奈米柱密度較高，這可以歸因於形成奈米柱的機制。從X光繞射儀及拉曼光譜儀的量測結果可以確定CIGS NTRs仍然保有黃銅礦結構的結晶模式；而在能量散射光譜儀可以發現CIGS NTRs中鈉元素含量有顯著的提升；藉由傅立葉轉換紅外線光譜儀來討論光學性質發現CIGS NTRs擁有漸變折射率的特性，可以有效的降低反射率。另外，從電阻對溫度量測實驗發現CIGS NTRs的電性表現會優於CIGS。最後在超快激發-探測光譜觀察到CIGS NTRs的缺陷相關非輻射復合率較CIGS低，此歸因於鈉元素的鈍化以及包覆在奈米柱外層的銅空缺區域減少了載子的復合率。

In this thesis, We prepared copper indium gallium selenide (CIGS) thin films by excimer pulsed laser deposition (PLD). Then we created nano-tip arrays (NTRs) on CIGS thin film via ion-milling process. In SEM images, the highly Cu-rich regions around secondary phases (Cu2-xSe) show high density of nano-tip because of the mechanism of formation. From XRD and Raman spectroscopy, we can make sure that CIGS NTRs still have crystalline with the chalcopyrite structure. Increment of sodium in CIGS NTRs is found by EDS. We used FTIR to investigate the optical properties, finding the reflectance of CIGS NTRs decreased due to the gradual refractive index. Moreover, CIGS NTRs possess better electrical transportation which is confirmed by resistivity-temperature (RT) measurement. Finally from femtosecond pump-probe spectroscopy, we can observed that surface recombination in CIGS NTRs is suppressed by the passivation of sodium and Cu-depletion region.