離子液體敏化太陽電池分子動態模擬及性能預測研究

Molecular Simulation and Performance Prediction of Ionic Liquid Dye-Sensitized Solar Cells

陳永和(Yung-Ho Chen)

指導教授 ： 洪哲文

國立清華大學/工學院/動力機械工程學系/博士(2010年)

https://doi.org/10.6843/NTHU.2010.00381

摘要

本論文藉由整合微觀分子動力學及巨觀計算質傳數學模式，模擬離子液體染料敏化太陽電池(Dye-Sensitized Solar Cell, 簡稱DSSC)之離子傳遞特性及整體性能，除可探究微觀奈米尺度的電解質離子擴散性與導電性外，並藉由實驗驗證其正確性，提供一套多尺度、快速、簡易的參數研究工具。
由於染料敏化太陽電池內部電子激發與傳遞，受電解質氧化還原離子擴散速率與離子本身導電性能等因素，對整體太陽電池發電性能有很大的影響。因此，本論文先從微觀角度來建立染料敏化太陽電池的質傳模式，並探討其本身特性。並於奈米尺度下，建立染料敏化太陽電池電解質分子動力學模擬模式，利用量子力學半經驗公式計算電解質電荷分布情形以及分子結構，再經由分子動力學理論與統計熱力學計算電解質的擴散係數與離子導電性能，並使用旋轉電極量測電解質溶液之極限電流，藉以換算得到的擴散係數，由可接受的誤差，證實計算結果之正確性，再以不同操作環境進ㄧ步探討濃度及溫度等參數對擴散係數之關連性。
此外，本論文亦建立染料敏化太陽電池電解質巨觀質傳模式，利用微觀角度下所計算出的電解質擴散係數與離子導電性，以及質傳定律(Fick’s Law)，在陰極的部分以有限差分法推導離子溶液之濃度場，根據所消耗掉的電解質計算出其導電能力與發電性能，並預測不同操作狀況下的染料敏化太陽電池的發電性能(I-V)曲線與效率，並與實驗結果相互比較。經參數最佳化研究結果顯示[I-]濃度0.5M及[I3-]濃度0.055M在303K的狀況下，可得到最佳性能，若搭配其他參數調整下，如TiO2孔率0.45，量子效率增至1.0，整體太陽電池效率將有機會達至20%。

關鍵字

染料敏化 ； 太陽電池 ； 電解質 ； 分子動力學

並列摘要

This thesis presents an integration of molecular dynamics simulation with computational mass transfer to predict the voltage-current performance of dye-sensitized solar cells (DSSCs). Ionic liquid electrolytes are the major transport medium that transfers redox charges (typically iodide/ triiodide) between the anode and the cathode. The flux of the species in the electrolyte is mainly diffusion transport and may constrain the solar cell performance. Molecular dynamics simulation technique was employed to assess the diffusion coefficient and ionic conductivity of the charge transport. The ionic conductivity was compared with an experimental result carried out by a rotational electrode test. The diffusion coefficient was then input to a computational mass transfer code and the depletion of redox charges at the electrode can be calculated. Electrochemical performance of the solar cell is predicted and shows in good agreement with the experimental result.
In order to maximize the DSSC performance, optimization of the design parameters has to be done. The optimal ionic liquid concentration was found to be 0.5M for [I-] and 0.055M for [I3-] at 303K. The expected energy conversion efficiency of such kind of photoelectrochemical cells is able to reach 20%, if proper parameters are tuned further, such as the porosity of the porous TiO2 is set to 0.45, the quantum efficiency reaches unity and etc.

並列關鍵字

dye sensitized ； solar cell ； electrolyte ； molecular dynamics

參考文獻

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