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Plasmonic Nanostructures for Enhanced ZnO/Si Heterojunction Optoelectronic Devices.

机译：用于增强型ZnO / Si异质结光电器件的等离子纳米结构。

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摘要

The objective of this work focuses on ZnO and Al doped ZnO (AZO) thin film deposition and characterization, and developing reliable ZnO/Si heterojunction thin film optoelectronic devices. Producing and integration of plasmonic nanostructures were also studied for improving device performance with plasmonic light trapping effects.;Enhanced ZnO/Si heterojunction metal-semiconductor-metal (MSM) photodetectors with plasmonic Ag nanoparticles (NPs) were realized. Self-assembled Ag NPs with different sizes, densities and distributions were produced on the surface of ZnO/Si MSM photodetector devices. By tuning the characteristic of these NPs, a higher-performance MSM detector has been achieved with photocurrent enhancement up to 680%. The spectral enhancement was broadband from 350 nm to 850 nm.;To investigate the nanoplasmonic effects for enhanced solar cell devices, a relatively simple device structure, Si Schottky solar cell with the metal-insulator-semiconductor (MIS) structure, was studied first. By introducing Ag NPs and SiO2 spacer layers on top of Si Schottky solar cells, we demonstrated a positive and tunable light trapping effect introduced by metallic NPs. Enhanced light trapping effects at distinct resonance wavelengths were observed in the optical spectra of the plasmonic-enhanced devices. Electrical measurements confirmed the expected photocurrent improvement at these corresponding wavelengths. It was also revealed that the Ag NPs enhance the carrier generation rate inside of the Si active layer without sacrificing carrier collection efficiency of the device. The short-circuit current density (Jsc) of the best cell we obtained was improved from13.7 mA/cm2 to 19.7 mA/cm2, with an enhancement factor of 43.7%.;Periodic nanostructures formed with nanoimprint technique and annealing process were studies to utilize in the Al-ZnO/Si heterojunction solar cell devices. The size, inter-particle distance and shape of these nanostructures can be easily tuned by changing the Ag film thickness and deposition angle. These periodic nano-ellipsoid arrays provide an absorption enhancement by a factor of 83.8% over a wavelength range of 500-1000 nm. Theoretical simulations revealed that the electromagnetic field can be coupled between each two nanoparticles, which would contribute to the optical absorption enhancement. Thin film Al-ZnO/n-Si solar cells were fabricated. By introducing these well-designed Ag periodic nanostructures, device performance was enhanced in both visible and infrared (IR) wavelength regions.;To achieve more reliable Al-ZnO/n-Si solar cell devices, we developed a novel and simple approach to realize high performance AZO films. Thin Al films were deposited on ZnO surfaces, followed by thermal diffusion processes, introducing the Al doping into ZnO thin films. During the thermal diffusion process, the chemical state of Al on the surfaces can be converted to a fully oxidized state, resulting in high electrical conductivity of 6.2 Ω/sq and excellent transparency (96.5% at 550 nm), which is superior compared with previously reported values for indium tin oxide (ITO) and most reported transparent conducting electrode (TCE) materials. These AZO films were used to fabricate AZO/n-Si solar cells and boost the device power conversion efficiency from <1% to 2.56%. Finally, the thermal diffusion process and co-sputtering process were combined for AZO deposition, giving a precise control of Al doping in buffer AZO layers and a high electrical conductivity for top AZO layers. Thus, the AZO/n-Si heterojunction solar cell performance was further improved to 4.1%.
机译：这项工作的目标集中于ZnO和Al掺杂的ZnO（AZO）薄膜的沉积和表征，以及开发可靠的ZnO / Si异质结薄膜光电器件。还研究了等离子体的纳米结构的产生和集成，以提高器件的性能和等离子体的俘获光的效果。实现了具有等离子体Ag纳米颗粒的增强型ZnO / Si异质结金属-半导体-金属（MSM）光电探测器。在ZnO / Si MSM光电探测器的表面上产生了具有不同尺寸，密度和分布的自组装Ag NP。通过调节这些NP的特性，已实现了性能更高的MSM检测器，光电流增强了680％。光谱增强范围是从350 nm到850 nm的宽带。为了研究增强型太阳能电池器件的纳米等离子体效应，首先研究了一种相对简单的器件结构，即具有金属-绝缘体-半导体（MIS）结构的Si肖特基太阳能电池。通过在Si肖特基太阳能电池的顶部引入Ag NP和SiO2间隔层，我们证明了由金属NP引入的正可调光捕获效果。在等离激元增强型器件的光谱中观察到了在不同共振波长处增强的光捕获效应。电学测量证实了在这些相应波长下预期的光电流改善。还揭示了Ag NP提高了Si活性层内部的载流子产生速率，而没有牺牲器件的载流子收集效率。我们获得的最佳电池的短路电流密度（Jsc）从13.7 mA / cm2提高到19.7 mA / cm2，增强因子为43.7％。;研究了利用纳米压印技术和退火工艺形成的周期性纳米结构在Al-ZnO / Si异质结太阳能电池器件中使用。这些纳米结构的尺寸，粒子间距离和形状可以通过改变Ag膜的厚度和沉积角度来容易地调整。这些周期性的纳米椭圆体阵列在500-1000 nm的波长范围内提供了83.8％的吸收增强。理论仿真表明，电磁场可以在每两个纳米颗粒之间耦合，这将有助于光学吸收的增强。制备了薄膜Al-ZnO / n-Si太阳能电池。通过引入这些设计良好的Ag周期纳米结构，器件在可见光和红外（IR）波长区域内的性能均得到了增强。为了获得更可靠的Al-ZnO / n-Si太阳能电池器件，我们开发了一种新颖且简单的方法来实现高性能AZO膜。将铝薄膜沉积在ZnO表面上，然后进行热扩散工艺，将Al掺杂引入ZnO薄膜中。在热扩散过程中，表面上的Al的化学状态可以转换为完全氧化的状态，从而产生6.2Ω/ sq的高电导率和优异的透明度（在550 nm下为96.5％），与以前报道的铟锡氧化物（ITO）和大多数报道的透明导电电极（TCE）材料的值。这些AZO膜用于制造AZO / n-Si太阳能电池，并将器件功率转换效率从<1％提高到2.56％。最后，将热扩散过程和共溅射过程结合在一起进行AZO沉积，从而可以精确控制缓冲AZO层中的Al掺杂，并为顶层AZO层提供高电导率。因此，AZO / n-Si异质结太阳能电池的性能进一步提高到4.1％。

著录项

  • 作者

    Tong, Chong.;

  • 作者单位

    State University of New York at Buffalo.;

  • 授予单位 State University of New York at Buffalo.;
  • 学科 Electrical engineering.;Nanotechnology.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 167 p.
  • 总页数 167
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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