指叉式背電極太陽能電池及全方向抗反射結構之模擬分析

Abstract

本篇論文著重在太陽能電池藉由模擬來分析及優化太陽能電池。透過模擬可以降低優化太陽能電池之成本及提供製程優化方向。在此，我們將利用TCAD模擬軟體開發並模擬新結構以增進電池之效率。 在第二章中主要探討N型指叉式背電極太陽能電池之二維模擬。藉由改變此電池結構的設計來增加電池的效率，例如最佳化射極和背電場之間距，射極的比例以及週期。此外，將電池之射極及背電場改為選擇性高摻雜可進一步提升電池的效率。電池中表面電場的效應也將於此章探討。在第三章中，我們開發了一種新的太陽能電池結構。此結構結合了指叉式背電極太陽能電池及異質接面太陽能電池之優點，我們稱之為混合型指叉式背電極太陽能電池。此種電池除了結構設計會影響效率外，非晶矽之能隙也是影響電池效率的重要參數。因此除了結構之優化，我們也會著重在非晶矽之能隙之模擬。第四章則是探討不同的表面結構在不同角度下之效應。此章的目的是發展出一個全方向抗反射之表面結構，使電池即使在光非垂直入射時也能有良好的光電轉換效率。藉由模擬微米球及在傳統紋理結構鋪上奈米球等結構構並優化結構設計找出能在不同入射角度下都能有良好的光侷限能力之結構設計

It is very helpful to analyze and optimize the solar cells by simulation. Through modeling and simulation, the performances of new photovoltaic devices and be predicted and guidelines can be provided without fabrication. The goals of this thesis are to optimize solar cells and develop new structures by numerical simulations using state-of-the-art technology computer aided design (TCAD) simulator to provide ideas to improve the performances of cells. Firstly, we discuss the designs of n-type interdigitated back contact (IBC) silicon solar cells through 2-D simulations. The aim is to improve cells’ efficiency through different designs by simulations. We optimize the gap size, the emitter ratio and the pitch. Then, we use the selective heavily doped emitter and back surface field (BSF) to further improve the cells’ efficiency. We also look into the effect of the front surface field (FSF). From the simulations, higher emitter ratio, smaller gap and using selective heavily doped emitter and BSF play an important role in attaining high efficiency. Secondly, we develop and simulate a new structure, hybrid IBC, which combines the advantages of IBC solar cells and heterojunction with intrinsic thin layer (HIT) solar cells. We investigate some issues that will affect the cells’ performances. For this kind of structure, in addition to the designs of the cell, the band gap of amorphous silicon (a-Si) is also an important factor that affects the cells’ performances. Therefore, we not only discuss the device optimizations but also emphasize on the band gap of intrinsic and p-type a-Si here. Finally, the angular effects of cells with different surface structures are given an in-depth study. The aim is to develop an omnidirectional antireflection surface structure which can perform well at all incident angles. To perform well at all incident angles, the structure should not only have angular independent performance but also good light trapping effect to achieve high Jsc and high performance. Different kinds of surface structures are under investigation such as texture, micro-spheres and texture with nano-spheres surface structures.