二氧化矽奈米柱結構應用於氮化銦鎵太陽能電池元件之研究

Efficiency Improvement of InGaN-based Solar Cell Device with Embedded SiO2 Nanorods Structures in GaN

阮詠禎(Yung-chen Juan)

指導教授 ： 郭政煌

國立中央大學/理學院/光電科學研究所/碩士(2011年)

摘要

本論文一開始針對嵌入二氧化矽圖樣化於氮化鎵薄膜，藉由側向磊晶(ELOG)方式成長氮化鎵薄膜可提升晶體品質，藉由XRD ω-rocking curve量測與單位面積缺陷數(EPD)量測氮化鎵薄膜分析結果，得到嵌入週期為SiO2/GaN＝2μm/1μm二氧化矽奈米柱條狀化的半高寬為275 arcsecs、單位面積缺陷數為3.1x108 cm-2，相較於傳統氮化鎵薄膜的半高寬為329 arcsecs、單位面積缺陷數為5.1x108 cm-2，從結果可以說明二氧化矽奈米柱條狀化於氮化鎵薄膜中，確實可以提升氮化鎵薄膜晶格品質。 接著探討嵌入二氧化矽圖樣化於氮化銦鎵太陽能電池元件之比較，其中嵌入週期為SiO2/GaN＝2μm/1μm二氧化矽奈米柱條狀化有最佳光電特性，開路電壓1.78 V、短路電流密度0.52 mA/cm2、填充因子47 %、轉換效率0.44 %，相較於傳統氮化銦鎵太陽能電池元件轉換效率提升29 %，因為嵌入二氧化矽奈米柱條狀化結構於氮化銦鎵太陽能電池元件中，不但可以提升氮化鎵薄膜品質而提升開路電壓，而且嵌入不同介質增加光反射，再次到達吸收層吸收，提升短路電流密度，進而提升氮化銦鎵太陽能電池元件轉換效率。 將二氧化矽奈米柱條狀化於氮化銦鎵太陽能電池元件中，再利用二氧化矽鈍化氮化銦鎵太陽能電池元件側壁，元件開路電壓為1.80 V，相較傳統氮化銦鎵太陽能電池開路電壓提升1.1 %；轉換效率0.45 %，相較於傳統氮化銦鎵太陽能電池元件轉換效率提升2 %。因為利用二氧化矽包覆元件側壁懸浮鍵增加並聯電阻，減少非輻射復合及元件漏電流產生。 接著探討平台蝕刻深度影響氮化銦鎵太陽能電池元件電性分析，平台蝕刻深度840 nm有最佳光電特性，短路電流密度為0.57 mA/cm2，相較於傳統氮化銦鎵太陽能電池提升提升11.7 %；轉換效率相較於傳統提升15 %。因為改變氮化銦鎵太陽能電池元件經照光產生電子電洞對往負極(n極)移動時所需傳遞的擴散距離，載子在傳輸時，距離越短會減少被材料缺陷捕捉的機率而造成短路電流密度增加，進而提升轉換效率。 最後將二氧化矽奈米柱條狀化結構運用於具二氧化矽側壁鈍化，且平台蝕刻深度為840 nm之氮化銦鎵太陽能電池元件，可得到最理想氮化銦鎵太陽能電池元件光電特性，開路電壓1.90 V、短路電流密度0.57 mA/cm2、填充因子45 %、轉換效率0.48 %，相較於傳統氮化銦鎵太陽能電池元件轉換效率提升41 %。

關鍵字

太陽能電池 ； 氮化鎵 ； 二氧化矽 ； 奈米柱

並列摘要

In this study, the GaN thin films with embedded SiO2 nanorods stripes by epitaxial lateral overgrown (ELOG) technology. According to full-width at half-maximum (FWHM) of X-ray ω-rocking curve of GaN (102) and AFM measurements, the dislocation density of GaN epilayers grown on the SiO2 pattern/GaN template was lower than those of the GaN/sapphire. Thus the etching pits density of the GaN films with embedded SiO2 nanorods stripes can be estimated to be approximately of 3.1 x108 cm-2, which is less than that of the conventional GaN films (5.1x108 cm-2). And the FWHM (275 arcsecs) of the GaN films with embedded SiO2 nanorods stripes was narrower than that (329 arcsecs) of the conventional GaN films. As a result, epitaxial lateral overgrown (ELOG) technology was developed to reduce threading dislocations.
InGaN-based Solar cell devices with embedded SiO2 rods stripes in GaN. The device shows significant improvement in current density from 0.44 to 0.52 mA/cm2 and an increment in conversion efficiency from 0.34% to 0.44%. Compared with conventional solar cell device, the conversion efficiency of solar cell device was enhanced 29%. To further enhance light absorption of the InGaN-based solar cell, a highly reflective SiO2 rods stripes structure was embedded in GaN. The origin for the photocurrent enhancement in the solar cell is related to reflection of light by SiO2 nanorods stripes structure.
The solar cell device with sidewall passivaiton, that with VOC = 1.80 V, conversion efficiency = 0.45 %. Compared with conventional solar cell device, that conversion efficiency was enhanced 2%. The SiO2 was used to passivite dangling bonds on the GaN sidewall with SiO2, that nonradiative recombination and leakage current of solar cell device was reduced.
The mesa height of solar cell device was 840nm, that with JSC = 0.57 mA/cm2, conversion efficiency = 0.48 %. Compared with conventional solar cell device, that JSC was enhanced 11.7%, and conversion efficiency was enhanced 15%. When carrier diffusion length was decreased, JSC increased due to the enhancement of conversion efficiency resulting from the decreasing distance between the p-side and n-side electrodes.
The InGaN-based solar cell device with embedded SiO2 nanorods stripes, that mesa height of solar cell device was 840nm, and then with sidewall passivation. The optimal electrical and optical properties of solar cell with JSC = 0.57 mA/cm2, VOC = 1.90 V, FF = 0.45 and conversion efficiency = 0.48 %. Compared with conventional solar cell device, that conversion efficiency was enhanced 41%.

並列關鍵字

solar cell ； GaN ； SiO2 ； nanorod

參考文獻

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