Title: 考慮表面缺陷之奈米尺度太陽能電池模擬
Simulation of Nano-scale Solar cell with Surface Defects
Authors: 林仕禮
Lin, Shih-Li
Lin, Chien-Chung
Keywords: 太陽能電池;表面缺陷;介面態;奈米;模擬;載子蒐集率;solar cell;surface defects;interface states;nano-scale;simulation;charge collection probability
Issue Date: 2015
Abstract: 對於奈米尺度太陽能電池而言,因為表面面積對體積的比例較高,所以介面缺陷對電池效能的影響比起傳統的矽基太陽能電池來得更大。這些缺陷往往會在介面處形成複合中心,使表面處產生複合電流,降低電池輸出的電流,當介面態的密度過高,不僅會產成Fermi-level pinning的效應,還會增加表面載子的複合速率,進而降低太陽能電池的效率。在已知的文獻有很多關於表面缺陷、Fermi -level pinning及表面複合速率的研究,三者之間也有某種程度的關聯,但相關的討論都只屬於定性的描述,而非定量的分析。在這篇論文中,我們提供了一種定性且定量的方式來研究表面態分佈對表面複合速率、Fermi-level pinning 及電池效率的影響,這種分析方式建立在已知的Disorder-induced gap state (DIGS) 模型上,使得三者的關係能用定量的方法明確地建立起來。因此,只要透過這種方法去量測金屬與半導體接面的介面缺陷分佈的型態,就能模擬出不同的介面態缺陷分佈會造成的pinning與表面複合速率,進而利用Matlab®軟體建立的數值模型計算出光電轉換效率。 對於光電轉換元件而言,載子收集率代表光生載子能夠順利被元件蒐集並流到外部電路的機會,因此會直接影響到電池輸出的光電流。由於載子收集率並無法直接用儀器量測,本篇論文採用數種不同的模型來模擬GaAs及Si太陽能電池的載子收集率,並針對結果來驗證模型的真實性。
For the nano-scale solar, the cell performance is more sensitive to the defects at the interface compared with the traditional silicon-based solar cells because of the large surface-to-volume ratio. These defects usually play a role of the recombination centers, thus lead to a recombination current at the surface and lower the output current. When the density of the interface states is very high, the pinning of the Fermi-level as well as the increasing recombination velocity occur, which would decrease the efficiency of the solar cells. There are many published papers about the surface defect, Fermi-level pinning, and the surface recombination velocity. These research indicated that there must be some relation among them, but the previous researched are limited within qualitative description, not quantitative analysis. In the thesis, we apply a method to study the effect of the distribution of the surface state on the surface recombination velocity, Femi-level pinning and efficiency qualitatively and quantitatively. This method is based on the existed model of Disorder-induced gap state (DIGS) and it can be used to build a relation among the three parts exactly. As a result, if we can measure the distribution of the interface defects at the metal-semiconductor interface, the effect of the density of the surface states on the surface recombination velocity and the pinning can be simulated and the according photon conversion efficiencies of the solar cells can also be calculated by the simulation program built on the MATLAB®. Solar cell is a kind of photoelectric device, the charge collection probability means the possibility that a photon-generated carriers can contribute to the external circuit, and thus it would affect the final output current. Because the collection probability cannot be measured directly by experiment, we turn to many model to simulate the collection probability of the GaAs and Si solar cells. Based on the result, we can testify the validity of these models.
URI: http://etd.lib.nctu.edu.tw/cdrfb3/record/nctu/#GT070258103
Appears in Collections:Thesis