第五章 結論以及未來展望
5.2 未來展望
本研究所表達的是利用目前現有的P3HT:PCBM 材料來製作高效率的 透明有機太陽能電池，以及其延伸應用探討。但同樣的也因為P3HT:PCBM 這層材料的透光性不佳，將來若是發展出新的材料其吸收光譜能夠不涵蓋 可見光的光譜，同時又具有很好的紅外光或是紫外光的吸收率，不僅效率 能夠兼顧，同時也能達到最佳的透光性，增加透明太陽能元件應用在建築 物表面的效應，達到最大的空間應用。而且對於堆疊結構仍然有可以改進 的空間，若是具有和 P3HT:PCBM 有不同的吸收光譜，如下圖 5-1 所示，
利用不同的吸收光譜達到涵蓋所有太陽能光譜的能力，如此可以增加不同 光譜的吸收應用，對於堆疊結構元件來說也有很好的效率提昇。
圖5- 1 P3HT/PCBM 高分子薄膜的吸收光譜與太陽放射光譜的比較圖
雖然就目前高分子有機太陽能電池之光電轉換效率來說，已經可以達 到相當好的光電轉換效率，但由於P3HT能帶寬為 1.9eV，主要主吸收在 600 nm光譜以下，而就太陽光譜來看，由圖 5-1 所示，有相當大的部份是在大 於600 nm波長的能量分佈，因此，開發出新的低能帶寬高分子材料，且能
階與acceptor相匹配，擁有高的載子遷移率是未來該領域的趨勢。在 2006 年 ，C. J. Brabec 等 人 在 Advanced Materials 期 刊 發 表 了 一 篇 ， 利 用 Voc =(1/ )(e EDonorHOMO − EPCBMLUMO) 0.3− V [51]公式推知在固定Acceptor 為PCBM時，當降低donor材料的HOMO能階，可以得到最大的開路電壓 值，此外利用固定donor的HOMO能階為-5.7eV去估計光電轉換效率極限，
當donor的LUMO能階降低時，能帶寬(Eg)也隨之降低，且在能帶寬小於 1.8eV時，可使高分子光伏電池光電轉換效率高達 10%(圖 5-2)。相信在未 來更有機會達到實際運用的光電轉換效率。另一方面，在追求高轉換效率 的同時，材料本身的耐熱性、耐久性及穩定性勢必也將成為未來有機太陽 能電池符合商品實際應用上所必須面對的問題。最後，希望本研究內容所 提出的透明電極論點對國內外學術界與相關產業將有所貢獻，並且在未來 發展結合上述兩個提升轉換效率的方法，期許有機太陽能電池能夠在日常 生活中更普及化與更廣泛地應用。
圖5- 2 預測光電轉換效率與donor的LUMO能階關係，圖中顯示HOMO能 階固定在 5.7eV時，當LUMO能階降低至能帶寬小於 1.8eV，高分子光伏 電池轉換效率可達10 ％[51]
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