太陽電池中陷光材料和結構的研究

張曉丹 黃茜 陳新亮 陳永生

摘 要：高效率太陽電池的獲得是推動光伏產業得到進一步拓展的關鍵之一，如何充分利用太陽光，提高太陽電池的光譜吸收是提高電池效率的有效手段之一。透明導電窗口層材料作為薄膜太陽電池中的一層重要功能材料，其對太陽電池有源層的光吸收具有非常重要的作用。本研究前期圍繞著如何拓寬太陽光的寬譜透過、高的絨度散射、以及長波長光的利用等方面進行了詳細的研究，部分研究成果如下：1） 采用基于密度泛函理論的平面波贗勢方法對W摻雜ZnO材料進行了理論分析，并采用磁控濺射技術進行了WZO薄膜的實驗研究，理論與實驗結果表明，W能夠在ZnO中起到施主作用，獲得n型半導體特性，同時能帶簡并效應使其光學帶隙展寬；2）研究了低成本超生噴霧技術制備ZnO工藝中In摻雜量對IZO薄膜特性影響的研究：In的摻入能有效提高ZnO薄膜的載流子遷移率，從而降低薄膜的電阻率，同時In的摻入具有抑制（002）晶面生長，促進（101）晶面生長的作用，使其具有良好的陷光效果；3） 通過優化ZnO緩沖層（buffer layer），有效地改善了LPCVD-ZnO：B的光電特性。結果表明：“富氧”的緩沖層有效地增加了ZnO：B-TCO的近紅外區域透過率，使其更適應寬光譜薄膜太陽電池的發展要求；4）提出了一類基于磁控濺射及LPCVD技術的具有復合陷光結構的ZnO前電極材料，并在疊層薄膜太陽電池中進行初步應用；5）基于復合陷光結構的優勢，采用磁控濺射技術，通過對沉積條件的有效控制以及后濕法腐蝕工藝的優化，獲得了大坑、小坑兼有的高絨度的ZnO透明導電薄膜，將其應用于非晶硅/非晶硅鍺/微晶硅三結電池中，初始效率達到了14.06%；6） 采用化學水浴法制備了PbS量子點材料，并對反應條件對樣品的影響進行了系統的研究，確定了將PbS等IV-VI族化合物半導體量子點用于上轉換器的具體技術途徑。

關鍵詞：太陽電池 光管理 氧化鋅 絨面結構 上轉換

Abstract：The most effective way to promote the PV industry is to improve the efficiency of solar cells. Increasing optical utilization and spectral absorption can improve the efficiency of wide-spectrum thin film solar cells. In the former period， the main research contents of this project are focus on how to widen the optical transmittances， obtain high haze values and increase the optical utilization in the long wavelength region. Some typical research results are listed as follows： 1） Properties of high valence difference WZO have been investigated by means of plane wave pseudo-potential method based on the DFT and pulsed DC magnetron sputtering technique. The theoretical and practical results show that the Fermi level enters into the conduction band when doping W atoms into ZnO， indicating a typical n-type semiconductor characteristic and the optical band gap Eg increases significantly. 2） Influences of indium doping on the electrical， structural and optical properties of ZnO films prepared by ultrasonic spray pyrolysis have been investigated. Experimental results show that indium dopant can enhance the carrier mobility and （001） preferential orientation of ZnO thin films， which make the ZnO：In thin films more conductive and strong light-scattering. 3） The structural， electrical and optical properties of LPCVD-ZnO：B thin films have been ameliorated through using the ZnO buffer layer. The experimental results show that the "rich oxygen" buffer layer effectively increased the near infrared optical transmittance. 4） A double-period structure to improve light absorption and trapping has been proposed by combining MS ZnO and LPCVD-grown ZnO：B films. This kind of mutiscale-tpye ZnO films as front electrodes are preliminarily used in tandem solar cells. 5） A high-performance ZnO electrode with high conductivity， transmittance and haze radio has been prepared by magnetron sputtering and post wet-etching. Effective textured surface with large crater and small crater compound is detected which enhance the long and short wavelength light trapping efficiency synchronously. Using this ZnO as front contact， an a-Si：H/a-SiGe：H/μc-Si：H triple tandem solar cell was obtained with an efficiency of 14.06%. 6） Cubic PbS QDs have been synthesized by chemical bath deposition. The effects of the reaction conditions on the properties of PbS QDs are investigated in detail. Specific technical approaches have been achieved to enhance the performances of upconverter with PbS QDs.

Key word：solar cells；light management； ZnO； textured surface； up-conversion

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