本質區中的量子點對p-i-n太陽電池效率的影響

Abstract

本論文以GaAs p-i-n太陽能電池為結構基礎，將量子點埋入本質區，藉由改變單一量子點條件參數，探討量子點參數改變，對太陽能電池效率的影響。首先我們建立了量子點太陽能電池模型，透過量子點吸收係數、量子點製成原理和結構的研究，總結出六項量子點參數：大小、體積誤差、形狀、材料、面密度、spacer厚度，接著依序調變各個參數，瞭解量子點參數對效率的影響，以及它們會如何改變開路電壓、短路電流和電流密度－電壓關係曲線，並與傳統同質太陽能電池做比較。緊接著，架構出埋入兩種不同材料的量子點的太陽電池模型，研究在不同量子點條件的搭配下，諸如：大小、體積誤差、形狀等等參數，對太陽電池效率的影響。依照上述架構，針對吸收係數強度與吸收波段分佈，分析太陽能效率參數變化，並和單種量子點太陽能電池以及同質太陽能電池做比較。最後可以歸納出，單種量子點對效率的影響程度大小次序：面密度≧大小＞體積誤差≧spacer厚度。除此之外，要令混和量子點太陽電池有最佳化的效率，需要注意量子點吸收係數的組合、吸收係數強度匹配光通量的分佈，以及增加具備吸收優勢的量子點層數比例 。

Embedding quantum dots in the i-region of the GaAs p-i-n solar cells(SC), we change the quantum dot parameters one at a time to understand how does quantum dot affect the performance of quantum dot solar cells(QDSC).First, we construct the model of QDSC .By studying the theory of quantum dot absorption coefficient, the fabrication of quantum dot and the device structure, we can conclude that there are six quantum dot parameters: size, volume fluctuation, shape, materials, surface density, and spacer thickness .We alter quantum dot parameters to understand whether the particular parameter will increase the SC efficiency or not .This can also shows that how it changes open circuit voltage, short circuit current, and current density-voltage curve .And we compare the efficiency to the traditional GaAs p-i-n SC .After that, we construct a QDSC model which has quantum dots with two materials .Using the model to study under different conditions what will happen to the SC efficiency. Through the absorption coefficient intensity and absorption wavelength distribution, we analyze the variation on the SC efficiency and compare it to the single type quantum dot SC and the traditional GaAs SC. At last we can sum up that the influence degree of each quantum dot parameter on efficiency is: surface density ≧ size ＞size fluctuation ＞spacer thickness. Besides, to have the maximum efficiency of the two materials quantum dot SC, we need to consider the combination of quantum dot absorption coefficients, the match between the absorption coefficient intensity and the light flux distribution, and we can also increase the stack number of the quantum dots with better absorption.