本文關(guān)鍵詞：基于應(yīng)變與摻雜設(shè)計高效光伏材料　出處：《蘇州科技大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 鈣鈦礦 過渡金屬氧化物 應(yīng)變 摻雜 太陽能電池材料

【摘要】：高效利用太陽能是解決能源危機和環(huán)境問題的最佳途徑。通過應(yīng)變和摻雜調(diào)控材料帶隙,提高太陽能吸收效率是當(dāng)前的研究熱點。本論文用第一性原理方法,研究應(yīng)變對SrTcO_3帶隙的影響、摻雜對BaTiO_3帶隙的影響,探討它們用作太陽能電池材料的可能性。第一章回顧了一些太陽能電池材料的研究歷程;第二章介紹了本文所涉及的理論和計算方法,包括密度泛函理論、局域密度近似(LDA)、廣義梯度近似(GGA)和雜化密度泛函(HSE)方法;第三章用GGA+U方法研究了SrTcO_3在雙軸應(yīng)變下的電子結(jié)構(gòu),討論了應(yīng)變對帶隙的調(diào)控;第四章用雜化密度泛函方法研究了摻雜對BaTiO_3帶隙的調(diào)控。第五章為總結(jié)與展望。在第三章中,用GGA+U方法探索了雙軸應(yīng)變對SrTcO_3帶隙的調(diào)控及調(diào)控機理。結(jié)果表明,無論是壓縮應(yīng)變還是拉伸應(yīng)變,體系的光學(xué)帶隙都減小。當(dāng)SrTcO_3生長在四種常用基片SrTiO_3(STO)/La_(0.3)Sr_(0.7)Al_(0.35)Ta_(0.35)O_9(LSAT)/NdGaO_3(NGO)/La Al O3(LAO)上,帶隙值變?yōu)?.56/1.47/1.43/1.12 eV,符合高效太陽能電池材料帶隙范圍。由電子結(jié)構(gòu)分析,可得到帶隙調(diào)控的機理:壓縮應(yīng)變增強時,導(dǎo)帶底(源于Tc原子的d3z2-r2態(tài))向費米能級移動,而價帶頂(源于dyz態(tài))基本不移動,使帶隙降低。在第四章中,用HSE方法計算得到BaTiO_3的帶隙為3.3 eV,與實驗值(3.4 eV)符合得很好。用該方法研究Co單摻雜、Pd單摻雜以及(Co,Pd)共摻雜對體材料BaTiO_3帶隙的影響。發(fā)現(xiàn)有4種體系符合高效太陽能電池材料的帶隙要求:BaTi_(0.875)Pd_(0.125)O_3、BaTi_(0.875)Co_(0.125)O_(2.875)、BaTi_(0.75)Co_(0.125)Pd_(0.125)O_(2.75)、BaTi_(0.926)Co_(0.037)Pd_(0.037)O_(2.926)帶隙分別為1.95 eV、1.85 eV、1.95 eV、1.90 eV。電子結(jié)構(gòu)分析表明,Pd摻雜引入的Pd_4d態(tài)提供新的導(dǎo)帶底,比原來Ti_3d導(dǎo)帶底更靠近費米面,從而降低帶隙。對于Co摻雜情形,Co_3d能帶稍稍跨過費米面,產(chǎn)生部分空穴,當(dāng)氧空位存在,氧空位提供的電子填滿這些空穴,產(chǎn)生新的能級較高的價帶頂,使帶隙減小。對于(Co,Pd)共摻雜情形,價帶頂升高與導(dǎo)帶底降低同時發(fā)生,使帶隙大大減小。本論文工作可為研制高效太陽能電池材料提供重要的理論依據(jù)。
[Abstract]:The efficient use of solar energy is the best way to solve the energy crisis and environmental problems. It is a hot topic to improve the efficiency of solar energy absorption by adjusting the band gap of material by strain and doping. In this paper, the first principles method is used to study the effect of strain on the SrTcO_3 band gap and the influence of doping on the BaTiO_3 band gap, and to explore the possibility of them being used as solar cell materials. The first chapter reviews some of the solar cell materials research progress; the second chapter introduces the theory and method mentioned in this article, including density functional theory, local density approximation (LDA) and generalized gradient approximation (GGA) and hybrid density functional (HSE) method; the third chapter studies the electronic structure of SrTcO_3 under biaxial strain using GGA+U method, discusses the regulation of strain on the band gap; the fourth chapter studies the regulation of BaTiO_3 doping on the band gap by using the hybrid density functional method. The fifth chapter is the summary and prospect. In the third chapter, the GGA+U method is used to explore the regulation and regulation mechanism of SrTcO_3 band gap with biaxial strain. The results show that both the compression strain and the tensile strain decrease the optical band gap of the system. When SrTcO_3 is grown on four commonly used substrates, SrTiO_3 (STO) /La_ (0.3) Sr_ (0.7) Al_ (0.35) Ta_ (0.35) O_9 (LSAT) /NdGaO_3 (NGO), LSAT, the band gap value is changed to zero, which is consistent with the high efficiency solar cell material band gap range. The mechanism of band gap control can be obtained by analyzing the electronic structure. When the compression strain is enhanced, the conduction band bottom (the d3z2-r2 state from Tc atom) moves to Fermi level, while the valence band top (from dyz state) basically does not move and makes the band gap decrease. In the fourth chapter, the band gap of BaTiO_3 is calculated by HSE method. The band gap is 3.3 eV, which is in good agreement with the experimental value (3.4 eV). The effect of Co single doping, Pd single doping and (Co, Pd) Co doping on the BaTiO_3 band gap of the bulk material was investigated by this method. Find that there are 4 kinds of system meet the requirements of band gap high efficiency solar cell materials: BaTi_ (0.875) Pd_ (0.125) O_3, BaTi_ (0.875) Co_ (0.125) O_ (2.875), BaTi_ (0.75) Co_ (0.125) Pd_ (0.125) O_ (2.75), BaTi_ (0.926) Co_ (0.037) Pd_ (0.037) O_ (2.926) band gap were 1.95 eV, 1.85 eV, 1.95 eV, 1.90 eV. The analysis shows that the electronic structure of Pd doped Pd_4d state introduced new conduction band bottom, the bottom of the conduction band more than the original Ti_3d near the Fermi level, thereby reducing the gap. For Co doping, Co_3d band slightly cross fee of rice, which part of hole, when the oxygen vacancy exists, fill the hole oxygen vacancy provides electrons, produce new energy high valence band gap decreases, the. In the case of (Co, Pd) Co doping, the rise of the valence band top and the lower guide band lower at the same time, so that the band gap is greatly reduced. The work of this paper can provide an important theoretical basis for the development of high efficiency solar cell materials.
【學(xué)位授予單位】：蘇州科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM914.4;O482.3

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相關(guān)期刊論文 前1條

1 魏壽彬;趙麗;董兵海;萬麗;許祖勛;王亞蘭;;鈣鈦礦太陽能電池的研究進(jìn)展[J];材料導(dǎo)報;2015年S2期

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本文編號：1341407