利用電漿輔助式分子束磊晶系統成長硒化銅銦薄膜太陽能電池與特性分析

Growth and Characterization of CuInSe2 Thin Film Solar Cells by Plasma-Assisted Molecular Beam Epitaxy

黃孝元(Hsiao-Yuan Huang)

指導教授 ： 楊祝壽

大同大學/電機資訊學院/光電工程研究所/碩士(2011年)

摘要

利用電漿輔助式分子束磊晶系統成功的成長出硒化銅銦薄膜太陽能電池。太陽能電池的結構包括硒化銅銦主吸收層、硒化鋅緩衝層、高濃度摻雜銦的氧化鋅透明導電層，在相同的腔體及製程下完成。首先將硒化銅銦和硒化銦成長在砷化鎵(001)及鈉鈣玻璃上，探討其基本物理特性。
在硒化銦磊晶層上我們將成長溫度維持在380-400度。藉由改變銦與硒的比例成長出N型的三硒化二銦及硒化銦磊晶層。藉由X射線繞射儀和拉曼散射了解三硒化二銦及硒化銦的晶體結構，在銦/硒的比值為0.67和0.87之間時，出現三硒化二銦及硒化銦的的相變點。另外在20 K的環境下藉由光激螢光光譜得到光子能量2.141eV為自由激子的躍遷並且在變溫的過程中觀察能隙的變化。
在硒化銅銦磊晶層的部分我們將討論不同銅與銦的比例對硒化銅銦的影響。在成長期間我們將長晶溫度維持在480-520度，從X射線繞射儀發現到硒化銅銦為黃銅礦結構。在鈉鈣玻璃上成長的優選方向是以(112)面為主，而在砷化鎵(001)成長的是以(008)面。隨著銅/銦比值的增加，晶格常數隨之增加，主要是因為銅空缺減少所影響。在電性方面我們發現在銅與銦的比例小於0.88時呈現n型半導體，而大於0.88則為p型。此時載子濃度從1.6×1013 cm-3(電子) 變化到1.2×1022 cm-3(電洞)。在室溫下硒化銅銦薄膜太陽能電池在太陽光譜1.5 AM的條件下得到短路電流為22 mA/cm-1，開路電壓為107 mV，填充因子為45.9 %，其轉換效率為1.7 %。轉換效率不佳的原因可能是因為緩衝層的選擇、p與n之間介面及製程上的問題。

關鍵字

硒化銅銦 ； 太陽能電池 ； 分子束磊晶

並列摘要

CuInSe2 thin film solar cells were grown on Mo/soda-lime glass substrate by plasma-assisted molecular beam epitaxy. The solar cell including CIS absorber layer, ZnSe buffer-layer, and heavy In doped ZnO transparence conducting oxide are grown in one chamber. Firstly, CuInSe2 and InxSey epilayers were grown on GaAs(001) and soda-lime glass to study the fundamental physical properties and optimize the absorb layer for solar cell.
In InxSey epilayers, the growth temperatures were used at temperatures around 380-400℃. N-type In2Se3 and InSe were obtained by changing In/Se ratios. The crystal structure of γ-In2Se3 and InSe were defined by X-ray diffraction (XRD) and Raman spectroscopy. The phase transition between In2Se3 and InSe was obtained at 0.67≦In/Se ratio (x)≦0.87. At 20 K, in the photoluminescence of γ-In2Se3, the free exciton emissions was observed and located at 2.141 eV. When temperature changed from 20 to 300 K, the band gap of In2Se3 is varied from 2.141 to 1.916 eV.
In CuInSe2 epilayers, we discuss CuInSe2 with different Cu/In ratio. During the process, the growth temperatures were used at around 480~520℃. XRD shows CIS have chalcopyrite structure. The preferential orientation of CIS on soda-lime glass and GaAs(001) are (112) and (008), respectively. The lattice constant of CIS increases with Cu/In ratio due to the declined of copper vacancy. In the electrical properties, n-type CIS was obtained as Cu/In≦0.88. In contact, p-type CIS was obtained as Cu/In＞0.88. At the same time, the carrier concentration vary between 1.6×1013(electron) to 1.2×1022 cm-3(hole). In the CIS solar cells, the results obtained that Jsc=22 mA/cm-1, Voc=107 mV, FF=45.9 % and η=1.7 % under AM1.5 global solar spectra conditions at room temperature. The poor conversion efficiency may be due to the selection of buffer layer, interface of p-n function and process problem etc.

並列關鍵字

MBE ； solar cell ； CuInSe ； Molecular Beam Epitaxy

參考文獻

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