發(fā)布時(shí)間：2018-02-25 04:25

  本文關(guān)鍵詞： 太陽能電池 上轉(zhuǎn)換發(fā)光 NaYF4 第一性原理 水熱法　出處：《燕山大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：稀土摻雜上轉(zhuǎn)換材料可以將不能被硅太陽能電池吸收利用的紅外光轉(zhuǎn)換為能夠被其吸收利用的可見光，從而增加硅太陽能電池對太陽光譜的利用率。稀土摻雜上轉(zhuǎn)換材料的基質(zhì)和稀土摻雜元素均對其發(fā)光性質(zhì)有重要影響。本文通過第一性原理方法研究不同上轉(zhuǎn)換基質(zhì)材料及不同稀土元素?fù)诫s的NaYF4上轉(zhuǎn)換材料的性質(zhì)，并通過水熱法制備NaYF4:Er/Yb，研究反應(yīng)時(shí)間、反應(yīng)溫度及pH值對樣品物相和形貌的影響。確定最佳工藝參數(shù)后，分別制備NaYF4:Ho/Yb、 NaYF4:Er/Yb及NaYF4:Tm/Yb，并研究各個(gè)樣品的發(fā)光性質(zhì)。 通過對β-NaYF4、β-NaYbF4及β-NaLuF4三種上轉(zhuǎn)換基質(zhì)材料的第一性原理研究發(fā)現(xiàn)，β-NaLuF4體系的穩(wěn)定性高于其他兩個(gè)體系，β-NaYF4體系在紅外光區(qū)域的吸收率和反射率在三者中均為最低，這有利于減少激發(fā)光的損失，從而提高激發(fā)光利用率。 通過對Dy、Ho、Er、Tm、Yb五種不同稀土元素單摻雜的β-NaYF4體系的第一性原理研究發(fā)現(xiàn)，，五種不同離子摻雜后，體系的晶胞體積均略有減小。除了Yb摻雜體系在紅外光區(qū)域有較為明顯的吸收外，其他稀土摻雜體系在紅外光區(qū)域均無明顯吸收，這正是稀土單摻雜上轉(zhuǎn)換材料發(fā)光效率較低的原因之一。反射方面，在紅外光區(qū)域Yb摻雜體系反射最為明顯，Er摻雜體系反射率最低。 利用水熱法，通過在不同工藝參數(shù)下制備NaYF4:Er/Yb發(fā)現(xiàn)，反應(yīng)時(shí)間的延長以及酸性條件有利于β-NaYF4相的生成，隨著反應(yīng)溫度的提高，產(chǎn)物由α-NaYF4相逐漸轉(zhuǎn)變?yōu)棣?NaYF4相，并且溫度進(jìn)一步升高不會改變產(chǎn)物物相，但會使樣品中晶體缺陷增多，顆粒分散性變差。在反應(yīng)時(shí)間為24h，反應(yīng)溫度為180℃，pH=3的工藝條件下，制備NaYF4:Ho/Yb，NaYF4:Er/Yb及NaYF4:Tm/Yb，產(chǎn)物均為純β-NaYF4相，并且晶型完整。NaYF4:Tm/Yb在800nm處有非常強(qiáng)的發(fā)光峰，這一波長恰好處于硅太陽能電池對太陽光吸收利用率最高的波段，因此NaYF4:Tm/Yb對于提高硅太陽能電池光電轉(zhuǎn)換效率具有潛在的應(yīng)用價(jià)值。
[Abstract]:Rare earth doped upconversion materials can convert infrared light that cannot be absorbed by silicon solar cells into visible light that can be absorbed and utilized by silicon solar cells. In order to increase the utilization ratio of solar spectrum of silicon solar cells, the matrix and rare earth doped elements of rare earth doped up-conversion materials have important influence on their luminescent properties. In this paper, different up-conversion is studied by first-principles method. Properties of matrix materials and NaYF4 upconversion materials doped with different rare earth elements, The effects of reaction time, reaction temperature and pH value on the phase and morphology of NaYF4: er / Yb were studied. After determining the optimum process parameters, NaYF4: Hor-Yb, NaYF4:Er/Yb and NaYF4: Tm / Yb were prepared, and the luminescent properties of each sample were studied. Through the first principle study of 尾 -NaYF4, 尾 -NaYbF4 and 尾 -NaLuF4 upconversion matrix, it is found that the stability of 尾 -NaLuF4 system is higher than that of the other two systems, and the absorptivity and reflectivity of 尾 -NaYF4 system are the lowest in the infrared region. This is beneficial to reduce the loss of excitation light, thereby increasing the utilization rate of excitation light. Through the first principle study of the five 尾 -NaYF4 systems doped with different rare earth elements, it is found that the lattice volume of the system decreases slightly after doping with five different ions, except that the Yb doped system has obvious absorption in the infrared region. Other rare earth doped systems have no obvious absorption in the infrared region, which is one of the reasons for the low luminescence efficiency of rare earth mono-doped up-conversion materials. The reflectance of Yb doped Yb doped system is the most obvious in infrared region, and the reflectivity of er doped system is the lowest. By hydrothermal method, NaYF4:Er/Yb was prepared under different process parameters. It was found that the prolongation of reaction time and acidic conditions were favorable to the formation of 尾 -NaYF4 phase. With the increase of reaction temperature, the product gradually changed from 偽 -NaYF4 phase to 尾 -NaYF4 phase. Moreover, further increase of temperature will not change the phase of the product, but it will increase the crystal defects and the dispersion of the particles. Under the conditions of reaction time of 24 h and reaction temperature of 180 鈩

本文編號：1533016