含金屬光柵結構的非晶矽薄膜太陽電池中載子傳輸之模擬研究

Abstract

本文係以數值模擬方式，對一具有金屬光柵結構的非晶矽薄膜太陽能電池，在已知其內部之載子產生率的情況下，探討其內部載子傳輸現象。此太陽能電池由三部分組成，由外而內，依序是作為表面電極之氧化銦錫透明導電層、非晶矽半導體層與作為底部電極的金屬銀光柵層。本文中非晶矽半導體內的載子傳輸為一個二維的數值問題，吾人藉由Gummel迭代法來求算出一組滿足Poisson方程式以及電子與電洞之連續方程式的解。在每次迭代運算過程中，我們並非一舉求算二維區間的解，而是將二維問題近似為有限個彼此有關聯的一維問題，再利用已設計好的一維模型來進行重複性的計算，以求得二維區間的解。為了評估此太陽能電池的性能，我們亦模擬了具有相同體積的平板型參考太陽能電池。模擬結果顯示：具有光柵結構的太陽能電池之能量轉換效率確有增加，相較於對應的參考太陽能電池，最大能量轉換效率可從5.93%提升至8.24%，亦即約有39%之相對提升。

The carrier transport of a thin-film amorphous silicon (a-Si) solar cell with a metal grating is numerically simulated, for a given generation rate in the solar cell. The solar cell structure consists of three parts: an ITO layer as the top contact, an a-Si layer and a metal Ag grating layer as the back contact. It is a two-dimensional problem to simulate the carrier transport in the a-Si region. Using the Gummel iteration method, we get the self-consistent solutions of the electron and hole continuity equations and the Poisson equation for the entire region of a-Si. At each iteration step, we solve the two-dimensional problem by repeatedly using the related one-dimensional model. In other words, the equations are not solved simultaneously in the two-dimensional region to save the memory and computer time. The simulated results reveal that the maximum efficiency of such a solar cell is enhanced, as compared with the reference flat solar cell of the same volume of a-Si. For the maximum efficiency, it can be increased from 5.93% to 8.24%, with a relative enhancement of about 39%.