利用金奈米粒子之表面電漿效應提升非真空製程銅銦鎵硒太陽能電池之吸光特性及元件表現

Enhancement of Light Absorption by Plasmonic Nanoparticles For Non-Vacuum Cu(In,Ga)Se2/CuInSe2 Solar Cell

陳奕如(Yi-Ju Chen)

指導教授 ： 闕郁倫

國立清華大學/工學院/材料科學工程學系/碩士(2014年)

摘要

銅銦鎵硒(CIGS)為一種直接能隙材料，吸光範圍寬，做成太陽能電池具高光電轉換效率，目前世界紀錄為20.8%。CIGS太陽能電池材料中的銦、鎵、硒元素地球上含量稀少總量有限，故如何減少吸收層材料使用並保持高效率為目前研究重點之一。金屬粒子具表面電漿效應。當金屬粒子受光照產生表面電漿共振時，其對光散射及吸收的截面積均會增加。若將此粒子置於太陽能電池吸收層中可增加光被利用的機率，使元件整體表現提升。本研究利用金奈米粒子的表面電漿效應提高CIGS元件整體表現。並以薄膜光學性質的量測及模擬解釋表面電漿效應對元件的增益機制。因為金奈米粒子的散射及吸收效應使光被CIGS薄膜的利用率提高，加入金奈米粒子的元件其光電流及光電轉換效率均有顯著提升。如此作法可成功減少吸收層材料使用並有機會於未來做出高效率超薄型可撓式CIGS薄膜太陽能電池。

關鍵字

銅銦鎵硒太陽能電池 ； 表面電漿效應 ； 金奈米粒子

並列摘要

In this work, we successfully demonstrated plasmonic Cu(InGa)Se2-based thin film solar cell prepared by a non-vacuum process. Cu(In,Ga)Se2, (CIGS) is a direct band gap semiconductor material that can be used as the absorption layer in thin film solar cell with the highest efficiency of 20.8 % so far. In recent years, researchers have made a lot of efforts on reducing the usage of materials in order to reduce material cost. Many possible approaches have been adopted to light absorption management to maintain cell efficiency while reducing the thickness of these absorption layers, such as nanostructured surface. Plasmonic effect, which is one of approaches for light trapping, has been successfully applied on polymer tandem solar cell and Si solar.
In the first study, Au nanoparticles (Au NPs) were introduced into CIGS/CdS and CdS/iZnO of CIGS device, respectively. Based on angle-dependent reflectance measurement, an enhanced light absorption in the range of 400~600 nm can be observed, which is consistent with the increasing external quantum efficiencies (EQE) of these devices. 8.52% enhancement of short circuit current (Jsc) and 24.7% improvement of power conversion efficiency have been attained by the light trapping effect utilizing plasmonic effect.
However, it remains challenges for applying Au NPs into Cu(InGa)Se2-based solar cells because Au NPs will react with In and Cu during high temperature annealing processes. In order to address this issue, development of thermal-stable protection shell was developed in the second study of the thesis. In brief, Au@SiO2 NPs were mixed with CuInS2 nanocrystal ink homogenously and experienced at high temperature selenization process to form CISe2 thin film layer where the plasmonic CuInSe2 (CISe2) solar cell with enhanced conversion efficiency by employing Au-SiO2 core-shell nanoparticles (Au@SiO2 NPs) can be achieved. SEM images reveal that the SiO2 shell can protect Au NPs intact after the high temperature annealing process. Consequently, under AM1.5G irradiation, the short circuit current (Jsc), open circuit voltage (Voc) and power conversion efficiency (η) have been improved by 13 %, 5 % and 17 % in average, respectively. This work successfully demonstrated enhanced light absorption scheme utilizing the Au and Au@SiO2 NPs within chalcopyrite solar cells and may have beneficial potential to other thin film photovoltaic devices systems.

並列關鍵字

plasmonic ； CIGS solar rcell ； Au nanoparticles

參考文獻

33. Panthani, M. G.; Akhavan, V.; Goodfellow, B.; Schmidtke, J. P.; Dunn, L.; Dodabalapur, A.; Barbara, P. F.; Korgel, B. A., Synthesis of CuInS2, CuInSe2, and Cu(InxGa1-x)Se2 (CIGS) Nanocrystal “Inks” for Printable Photovoltaics. J. Am. Chem. Soc. 2008, 130 (49), 16770-16777.

1. Jackson, P.; Hariskos, D.; Wuerz, R.; Wischmann, W.; Powalla, M., Compositional investigation of potassium doped Cu(In,Ga)Se2 solar cells with efficiencies up to 20.8%. physica status solidi (RRL) – Rapid Research Letters 2014, 8 (3), 219-222.

2. Wei, S.-H.; Zhang, S. B.; Zunger, A., Effects of Ga addition to CuInSe2 on its electronic, structural, and defect properties. Appl. Phys. Lett. 1998, 72 (24), 3199-3201.

4. Igalson, M.; Zabierowski, P.; Prządo, D.; Urbaniak, A.; Edoff, M.; Shafarman, W. N., Understanding defect-related issues limiting efficiency of CIGS solar cells. Sol. Energy Mater. Sol. Cells 2009, 93 (8), 1290-1295.

5. Atwater, H. A.; Polman, A., Plasmonics for improved photovoltaic devices. Nat Mater 2010, 9 (3), 205-213.