稀土下轉換紅外螢光體之共沉澱合成、特性鑑定與其在太陽電池效率提升之應用

Abstract

下轉換紅外螢光體具有吸收短波長光子並轉換為兩個或兩個以上的長波長光子的特性，在太陽能電池光譜轉換技術具備應用潛力。太陽能電池主要響應的波段為紅外光區(950 nm ~ 1100 nm)，藉由下轉換紅外螢光粉轉換特性，預期能提升太陽電池之轉換效率，並改善電池在短波段的低頻譜響應與電池表面複合問題。 本研究首先利用共沉澱法成功合成次微米級下轉換Gd2O3: Bi3+, R3+ (R: Yb, Nd)螢光粉，在紫外光激發下放射藍光，再經由Bi3+→R3+能量傳遞放射紅外光。本論文藉由X-光粉末繞射圖譜、紅外與螢光光譜與掃描式電子顯微鏡影像等探討共沉澱製程中尿素計量與pH值實驗條件的改變對於螢光粉粒徑大小、粒徑形貌與材料微結構與光學性質的影響。此外，我們利用旋轉塗佈法將下轉移Gd2O3:Bi3+, R3+ (R: Yb, Nd)螢光粉沉積在太陽能電池上，並進行電流密度對電壓曲線量測之，分別探討此材料在有/無抗反射層的單晶矽與多晶矽太陽能電池轉換效率之變化。

Downconversion (DC) phosphors are characterized by the conversion of short-wavelength radiation to long-wavelength radiation. Due to the unique property, DC phosphors have been investigated as candidates for spectral converter to enhance the conversion efficiency of solar cells. The highest spectral response to solar radiation of silicon solar cells locates in the infrared region (950 -1100 nm). Therefore, DC IR-emitting phosphors can be integrated into solar cell to enhance the conversion efficiency and improve spectral response for the shorter wavelength. Through coprecipitation method, we have successfully synthesized submicron downconversion Gd2O3: Bi3+,R3+ (R: Yb, Nd) phosphors, which emit blue light excitation under UV excitation and then emit infrared through Bi3+→R3+ energy transfer process. We also investigated the effect of urea dosage and solution pH in the coprecipitation process on the size and morphology of particles of Gd2O3: Bi3+,R3+ by using XRD, IR and luminescence spectra and SEM. Furthermore, DC Gd2O3:Bi3+,R3+ (R: Yb, Nd) phosphors were spun-coated on c-Si solar cells whose J-V curves were measured to investigate the potential efficiency enhancement in single and polycrystalline Si solar cells with and without antireflective coating.