兩種金屬奈米粒表面電漿子薄矽太陽能電池特性之研究

Characterization of Plasmonics Thin-Si Solar Cells Using Two Type Metallic Nanoparticles

陳苑慈(Yuan-Tsz Chen)

指導教授 ： 何文章

國立臺北科技大學/電資學院/光電工程系研究所/碩士(2014年)

https://doi.org/10.6841/NTUT.2014.00348

摘要

本論文是藉由金屬奈米粒子表面電漿效應(Surface Plasmon Resonance, SPR)應用於薄矽太陽能電池之正、背面的特性研究。首先，在矽太陽能電池正面製作小顆粒的銦奈米粒子(Indium Nanoparticles, In NPs)於二氧化鈦(TiO2)空間層(Space Layer)上，透過入射光照射而激發產生SPR使電場侷域性增加，提升太陽能電池對短波長的光吸收，及於矽太陽能電池背面形成大顆粒的銀奈米粒子(Silver Nanoparticles, Ag NPs)，使長波長在背面產生侷域性表面電漿共振，將光散射回半導體內部進行再次吸收，結合兩種金屬粒子在正、背面SPR來提升太陽能電池之整體光電流(Photocurrent, Iph)及轉換效率(Conversion efficiency, η)。
本實驗利用旋轉塗佈(Spin-on Coating)法將含磷之薄膜形成在p--Si表面，以900℃磷擴散(Phosphor Diffusion)後在正面形成n+-Si Emitter。再蒸鍍覆蓋率60%格子狀的Al薄膜於電池背面與鈦(Ti)/鋁(Al)薄膜於正面形成金屬電極，完成裸矽太陽能電池。本研究，在裸矽太陽能電池正面，將銦奈米粒子蒸鍍在不同厚度的二氧化鈦空間層上，探討金屬奈米粒電漿子在不同厚度二氧化鈦空間層對太陽能電池之影響。由反射率及外部量子效率量測結果，發現當蒸鍍銦奈米粒子於較厚的二氧化鈦空間層上時，表面電漿共振會產生紅移現象。在AM 1.5G的太陽光環境下，也發現當二氧化鈦空間層厚度越厚，金屬奈米銦粒的SPR貢獻就越少。當銦奈米粒子蒸鍍於30 nm的二氧化鈦空間層上，其SPR貢獻較明顯，光電流密度提升率為10.85%，轉換效率提升率為12.34%。另外，在太陽能電池背面蒸鍍不同厚度的銀薄膜以及銀薄膜蒸鍍於二氧化鈦空間層上，再經熱退火形成銀奈米粒子的太陽能電池。經外部量子效率(External Quantum Efficiency, EQE)及照光I-V特性量測，發現直接蒸鍍30 nm的銀在裸矽太陽能電池的背面，外部量子效率及轉換效率提升最多。
最後，正面及背面以前述表面電漿子較佳條件製作在正、反面具金屬奈米粒子之單晶矽太陽能電池上，背面奈米銀粒表面電漿貢獻的光電流密度提升率(Enhancement)為3.69%及轉換效率提升率為3.77%；且在波長1000-1200 nm的外部量子效率平均提升率約為26.17%。正面奈米銦粒表面電漿貢獻光電流密度提升率為8.32%及轉換效率提升率為9.31%；且在波長350-700 nm為銦奈米粒子產生表面電漿共振最強的波段。當兩種金屬奈米粒子同時形成於單晶矽太陽能電池兩面時，整體特性相較於裸矽太陽能電池可使光電流密度提升率為31.59%，轉換效率提升率為32.72%。

關鍵字

金屬奈米粒子 ； 表面電漿子 ； 單晶矽太陽能電池 ； 二氧化鈦空間層 ； 外部量子效率

並列摘要

In this study, we report the photovoltaic performance of surface plasmon resonance (SPR), through using two different of metallic nanoparticles in the thin silicon solar cell. First, Indium nanoparticles (In-NPs) were evaporated on the front surface of TiO2 space layer, In-NPs SPR can be enhanced the optical absorption at short wavelength when the sunlight incident on the proposed solar cells, and silver nanoparticles (Ag- NPs) were evaporated on the rear surface, Ag-NPs SPR scatters the incident photons back into absorb semiconductor at long-wavelength band, which contributed by localized surface plasmon. Combining two type metallic nanoparticles of plasmonic effects of In-NPs and Ag-NPs, the short-circuit current and conversion efficiency of the plasmonics solar cell can be enhanced.
The first, we used the spin-on coating technology, which spin the phosphorus (P) diffusion source on the front side of p-Si wafer and annealed at 900℃ by RTA chamber. Secondly, the coverage of 60% of Al electrode on the rear side and Ti/Al electrode on front-side were evaporated by electron beam and annealed in the RTA chamber to obtain a good ohmic-contact. After annealing, the bare-type single-crystal silicon solar cell was obtained. The performance of the plasmonics silicon solar cell based on nano-sized indium-particles with different thickness of TiO2 space layer is investigated experimentally in this work. The reflectance and external quantum efficiency (EQE) measured results show that the solar cell with In-NPs on TiO2 space layer has a red-shift. Under AM1.5 illumination, the enhancement of the short-circuit current density (Jsc) and conversion efficiencies of the plasmonic Si solar cell with indium nanoparticles on the 30 nm TiO2 space layer are increased by 10.85% and 12.34%, respectively. In addition, the silver films with different thickness are deposited on the rear side surface and upon the TiO2 space layer and subsequently annealed to form Ag-NPs. The EQE response and photovoltaic I-V were measure as the solar cells with Ag-NPs. The results show that the cell with a 30 nm-thick silver film deposited on the rear surface exhibited the best improving in EQE and conversion efficiency.
Based on the previous experiment of the front and the rear side of the surface plasmon, the cell with Ag-NPs on the rear side surface shows that the photocurrent density efficiency enhancement of 3.69% and conversion efficiency enhancement of 3.77% are obtained, and an average EQE enhancement was approximately 26.17% at the wavelength range of 1000-1200 nm. On the other hand, the cell with In-NPs on the front side surface shows the photocurrent density enhancement of 8.32% and conversion efficiency enhanced by 9.31% are obtained. And a higher EQE enhancement was observed between the wavelength range of 350-700 nm. Finally, the overall photocurrent density enhancement of 31.59% and conversion efficiency enhancement of 32.72% was obtained when the plasmonics thin Si solar cell using In-NPs on the front surface and Ag-NPs on the rear surface.

並列關鍵字

Metallic Nanoparticles ； Surface Plasmon Resonance ； Single Crystal Silicon Solar Cell ； TiO2 Space Layer ； External Quantum Efficiency

參考文獻

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