薄膜太陽能電池的光捕捉最佳化之模擬研究

Abstract

近年來具有前瞻性太陽能電池的發展漸漸將奈微米結構應用在太陽能電池 元件，藉此用來降低入射光的反射，增加太陽光入射太陽能電池在粗糙表面的散 射，而達到太陽光在太陽能電池的吸收，這也是最近幾年來科學家注重的光捕捉 技術。光捕捉技術主要應用在薄膜矽太陽能電池，包含表面粗糙化、單層干涉、 多層膜設計或是奈米線等等，藉由這些結構增加太陽光在太陽能電池的行經路徑， 而得以增加太陽能電池的效率。 由於本篇很重要的概念是薄膜矽太陽能電池的光捕捉結構，在第二章我們會 介紹薄膜太陽能電池結構還有發電原理，當然也會詳細介紹光捕捉結構的原理， 包含繞射原理、太陽光在光柵表面的繞射、繞射效率等。而我們在以下兩個章節 的模擬，都是透過基因演算法來找到最佳化的結構，在這章也會詳細介紹基因演 算法的原理、應用，還有他模擬的方式。 在本文的第三章會介紹很常被拿來模擬太陽能電池的光性與電性的模擬軟 體，TCAD，在這邊我們只介紹這個軟體如何模擬太陽能電池的光性。而我們透過 TCAD 模擬軟體，架構一個可以找到太陽光捕捉的最佳化的流程。透過設定好太 陽能電池的結構跟參數，運用基因演算法不斷的計算，經過每一次 TCAD 的模擬 太陽能電池的吸收，一直重複這些步驟，直到找到最佳化的光捕捉結構。 在本文的第四章會介紹 RCWA( Rigorous coupled-wave analysis )的方法來計 算太陽能電池對太陽光的光吸收、反射等，不過我們最主要的目的還是想要用來 找到最佳化的光捕捉結構。而我們也一樣在太陽能電池的本質區鍍上光捕捉的結 構來提升太陽能電池的吸收，而運用類似第三章的方法，透過不斷的模擬跟基因 演算法基因演算法運算，來找到最佳化的光捕捉結構。 在本文的第五章會將第三、四章介紹的兩種最佳化方法做比較，哪一種方法 比較適用，也會對我們這個方法做歸納，之後的未來展望。

ii Simulation of Thin-Film Solar Cells for Optimization of Light Trapping Student：Shang-Ju Lin Advisors：Dr. Albert Shihchun Lin Department of Electronics Engineering & Institute of Electronics Engineering National Chiao Tung University ABSTRACT Recently, most scientists pay significant attention to nano-/micro-technologies of solar cells. The light trapping technologies are used to reduce the reflection of incident light, to scatter the incident light by rough surface, and to increase the absorption of solar cells. The light trapping technologies have the main applications for thin-film silicon solar cells, including using rough surfaces, single dielectric layer interference, design of multilayers, nanowires, and so on. In chapter two, we will introduce how the power of thin-film solar cell generate and the theories of light trapping structure in detail. These include the diffraction theories, the diffraction of sunlight on the surface, and the diffraction efficiencies. Afterward, we use genetic algorithm to find the optimal light trapping structure with two methods of simulation. We will also introduce the theories and applications of genetic algorithm, and how the optimal simulation process works. In chapter three, we will introduce the simulation software, TCAD, which is often used to compute the optical and electrical properties of solar cell. In this work, we only introduce the simulation of the optical properties. We set up an optimization process that we can find the optimal light trapping structure by TCAD. As long as we set the parameters and structures of solar cell, the optimal simulation process can help us find the optimal light trapping structure. In the optimization processes, that genetic algorithm calculates the solar cell absorbance continuously, and the structure is adjusted every time. By repeating this process, we will find the optimal light trapping structure.In chapter four, we use another method, RCWA( Rigorous coupled-wave analysis ), to calculate the reflection and absorption of the sunlight incident of solar cell, but the main purpose is still that we want to find the optimal light trapping structure. We use the method that is like the one we used in chapter three to find the optimal light trapping structure, through continuous simulations and calculations. In final chapter, we discuss and summarize the two optimization methods, and then we propose the future prospective of this work.