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首页> 外文学位 >Novel Materials, Grid Design Rule, and Characterization Methods for Multi-Junction Solar Cells.
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Novel Materials, Grid Design Rule, and Characterization Methods for Multi-Junction Solar Cells.

机译：多结太阳能电池的新型材料，网格设计规则和表征方法。

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摘要

This dissertation addresses challenges pertaining to multi-junction (MJ) solar cells from material development to device design and characterization.;Firstly, among the various methods to improve the energy conversion efficiency of MJ solar cells using, a novel approach proposed recently is to use II-VI (MgZnCd)(SeTe) and III-V (AlGaIn)(AsSb) semiconductors lattice-matched on GaSb or InAs substrates for current-matched subcells with minimal defect densities. CdSe/CdTe superlattices are proposed as a potential candidate for a subcell in the MJ solar cell designs using this material system, and therefore the material properties of the superlattices are studied. The high structural qualities of the superlattices are obtained from high resolution X-ray diffraction measurements and cross-sectional transmission electron microscopy images. The effective bandgap energies of the superlattices obtained from the photoluminescence (PL) measurements vary with the layer thicknesses, and are smaller than the bandgap energies of either the constituent material. Furthermore, the PL peak position measured at the steady state exhibits a blue shift that increases with the excess carrier concentration. These results confirm a strong type-II band edge alignment between CdSe and CdTe. The valence band offset between unstrained CdSe and CdTe is determined as 0.63 eV+/-0.06 eV by fitting the measured PL peak positions using the Kronig-Penney model. The blue shift in PL peak position is found to be primarily caused by the band bending effect based on self-consistent solutions of the Schrodinger and Poisson equations.;Secondly, the design of the contact grid layout is studied to maximize the power output and energy conversion efficiency for concentrator solar cells. Because the conventional minimum power loss method used for the contact design is not accurate in determining the series resistance loss, a method of using a distributed series resistance model to maximize the power output is proposed for the contact design. It is found that the junction recombination loss in addition to the series resistance loss and shadowing loss can significantly affect the contact layout. The optimal finger spacing and maximum efficiency calculated by the two methods are close, and the differences are dependent on the series resistance and saturation currents of solar cells.;Lastly, the accurate measurements of external quantum efficiency (EQE) are important for the design and development of MJ solar cells. However, the electrical and optical couplings between the subcells have caused EQE measurement artifacts. In order to interpret the measurement artifacts, DC and small signal models are built for the bias condition and the scan of chopped monochromatic light in the EQE measurements. Characterization methods are developed for the device parameters used in the models. The EQE measurement artifacts are found to be caused by the shunt and luminescence coupling effects, and can be minimized using proper voltage and light biases.;Novel measurement methods using a pulse voltage bias or a pulse light bias are invented to eliminate the EQE measurement artifacts. These measurement methods are nondestructive and easy to implement. The pulse voltage bias or pulse light bias is superimposed on the conventional DC voltage and light biases, in order to control the operating points of the subcells and counterbalance the effects of shunt and luminescence coupling. The methods are demonstrated for the first time to effectively eliminate the measurement artifacts.
机译：本文从材料开发到器件设计和表征等方面解决了多结太阳能电池的挑战。首先，在各种提高MJ太阳能电池能量转换效率的方法中，最近提出了一种新颖的方法。在GaSb或InAs基板上晶格匹配的II-VI（MgZnCd）（SeTe）和III-V（AlGaIn）（AsSb）半导体，用于电流匹配的子电池，具有最小的缺陷密度。在使用该材料系统的MJ太阳能电池设计中，CdSe / CdTe超晶格被提议作为子电池的潜在候选者，因此研究了超晶格的材料特性。超晶格的高结构质量是从高分辨率X射线衍射测量和横截面透射电子显微镜图像获得的。从光致发光（PL）测量获得的超晶格的有效带隙能量随层厚度而变化，并且小于任一种构成材料的带隙能量。此外，在稳态下测得的PL峰位置显示蓝移，该蓝移随过量的载流子浓度而增加。这些结果证实了CdSe和CdTe之间的强II型能带边缘对准。通过使用Kronig-Penney模型拟合测得的PL峰值位置，可以确定未应变CdSe和CdTe之间的价带偏移为0.63 eV +/- 0.06 eV。根据Schrodinger和Poisson方程的自洽解，发现PL峰值位置的蓝移主要是由带弯曲效应引起的;其次，研究了接触网格布局的设计，以最大化功率输出和能量聚光太阳能电池的转换效率。由于用于触点设计的常规最小功率损耗方法在确定串联电阻损耗时不准确，因此提出了一种使用分布式串联电阻模型来最大化功率输出的方法。已经发现，除了串联电阻损耗和遮蔽损耗之外，结的重组损耗还会显着影响触点布局。两种方法计算出的最佳手指间距和最大效率相近，其差异取决于太阳能电池的串联电阻和饱和电流。最后，外部量子效率（EQE）的准确测量对于设计和测量非常重要。 MJ太阳能电池的开发。然而，子电池之间的电和光耦合已引起EQE测量伪影。为了解释测量伪像，针对偏置条件和EQE测量中切碎的单色光的扫描建立了DC和小信号模型。针对模型中使用的设备参数开发了表征方法。发现EQE测量伪影是由分流和发光耦合效应引起的，并且可以使用适当的电压和光偏置将其最小化;发明了使用脉冲电压偏置或脉冲光偏置的新颖测量方法以消除EQE测量伪影。这些测量方法无损且易于实现。脉冲电压偏置或脉冲光偏置叠加在常规的直流电压和光偏置上，以控制子电池的工作点并平衡分流和发光耦合的影响。首次演示了这些方法，以有效消除测量伪影。

著录项

  • 作者

    Li, Jingjing.;

  • 作者单位

    Arizona State University.;

  • 授予单位 Arizona State University.;
  • 学科 Engineering Electronics and Electrical.
  • 学位 Ph.D.
  • 年度 2012
  • 页码 142 p.
  • 总页数 142
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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