表面電漿對太陽能電池吸收增加之應用

Enhanced Absorption by SPR for Solar Cell Application

蘇建維(Chien Wei Su)

指導教授 ： 蘇國棟

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.00748

摘要

表面電漿(surface plasmon resonance,簡稱SPR)是一個很特殊的光-物質混合現象。在金屬與介電物質的介面上，它能將入射光的能量轉換成局部放大的電場，使得他在很多方面都有很多應用，例如藝術品、生物感測器(biosensor)、資料儲存(data storage)、表面增強拉曼光譜(Surface Enhanced Raman Scattering，簡稱SERS)、奈米顯影技術(nanolithography)、治療、抗紅外線窗戶、太陽能電池、以及次波長光學(subwavelength optics)的相關研究。發生在金屬粒子的表面電漿現象(或簡稱粒子電漿)可以用米氏理論(Mie theory)來分析。我們可以調變奈米粒子的體積、形狀、間距，以及周圍的介電材料來改變粒子電漿的吸收波峰。

本文將介紹利用金奈米粒子所產生的表面電漿現象，增加太陽能電池對光吸收的程度。元件中，我們首先在ITO玻璃上鋪上一層直徑5nm的金奈米粒子層，於其上旋鍍p-type的PEDOT以減少金屬的功函數，以及n-type的MEHPPV和碳六十的混合物。

我們將成果分成米氏理論模擬的部份以及實驗證成的部份。模擬的結果可以幫助我們更了解我們元件中的表面電漿現象，同時也幫助我們預測其表面電漿的波峰位置，以及在可見光範圍中吸收增益的情形。實驗的部份，我們分成電流-電壓作圖的測量以及頻譜響應的分析。在有加金奈米粒子的有機太陽能電池中，由於對光的吸收增強，使得所量測到的光電流也增加。對比沒有加入金奈米粒子的元件，其增加的幅度在鹵素燈的照射下為40%，且波峰位置大致在335nm附近。這樣的結果非常符合理論模擬分析，使我們更確信表面電漿可在有機太陽能電池中發揮效用。
最後，我們介紹了兩種表面電將於有機太陽能電池中增益的機制，一者為電場效應，另一種為加熱效應。因為此種增益的機制尚未被徹底的研究，因此未來將會在這方面做更深入的探討與研究。

關鍵字

表面電漿 ； 有機太陽能電池

並列摘要

Surface plasmon resonance (SPR) is a unique light-matter hybrid interaction that will transfer absorbed incident light energy into local enhanced electric field at the interface of metal and dielectric materials. It is of great interest for a variety of applications in metallic nanoparticles such as artwork [1], biosensor [2], data storage, SERS [3], nanolithography [4], therapy [5], NIR-blocked window [6], solar cell, and other researches on subwavelength optics [7]-[8]. The SPR in metallic nanoparticles (say, particle plasmon) can be analyzed by Mie theory [9]. The peak absorption wavelength of particle plasmon can be controlled by nanoparticles’ size, shape, spacing, and local dielectric environment [10].

In this thesis, we will describe an engineered enhancement of optical absorption in an organic photovoltaic cell via the excitation of SPR in spherical Au nanoparticles deposited on a device surface. We deposited gold nanoparticles with 5 nm in diameter on ITO (indium tin oxide) glass substrates and then coated poly (styrenesulfonate) / poly(2,3-dihydro-thieno-1,4-dioxin) (PEDOT) which can reduce the work function of metal atoms and poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEHPPV) with Fullerene(C60) mixtures that work as p-type and n-type organic semiconductors, respectively.

We work on both Mie theory simulation and experimental confirmation. Simulation results will help us know more about SPR phenomenon in our case that we can predict its resonance peak and how large enhancement it is over visible range. In experiment part, we do the I-V curve measurement and spectrum response. The enhancement in electromagnetic field absorption within a device results in increased photocurrent response in organic p-n junction diodes with gold nanoparticles over wavelength ranges. Compared with the same organic photovoltaic structures without gold nanoparticles, the proposed device shows about 40% power efficiency improvement under halogen light illumination. Furthermore, the enhancement peak occurs near 335nm. This result answers well to the prediction of simulation, which convince us SPR really works in organic solar cell.

Finally, we introduce enhancement mechanism of electric field effect and heating effect. Because the mechanism has not been revealed clearly, we will investigate more about this topic in the future.

並列關鍵字

surface plasmon ； organic solar cell

參考文獻

[13]邱國斌、蔡定平,“左手材料奈米平板的表面電漿量子簡介“, 物理, 第二十五卷第三期, 373-382頁, 2003.

[21]C. So¨nnichsen, S. Geier, N. E. Hecker, G. von Plessen, J. Feldmann, H. Ditlbacher, B. Lamprecht, J. R. Krenn, and F. R. Aussenegg, V. Z-H. Chan, J. P. Spatz, and M. Mo¨ ller, “Spectroscopy of single metallic

[2]J Homola, SS Yee, G Gauglitz, “Surface plasmon resonance sensors: review”, Sensors and Actuators B: Chemical, 54, 3 – 15, 1999.

[3]Xu H,Bjerneld E L,Kall M,Borjesson L. “Spectroscopy of Single Hemoglobin Molecules by Surface Enhanced Raman Scattering”, Physical Review Letters, Vol 83, 4357, 1999.

[5]M.Cortie, X.Xu, H.Chowdhury, H.Zareie, and G.Smith, “Plasmonic heating of gold nanoparticles and its exploitation”, Proc. SPIE 5649, 565, 2005.