應用噻吩并[3,4-c]吡咯-4,6-二酮於主鏈施體－受體高分子之主體異質接面有機太陽能電池之研究

Abstract

基於對再生性能源的渴求，有機太陽能電池成為眾多應用太陽能研究之一重要類別。在元件結構上，為獲取最佳之能量轉換表現，在本實驗中採用總體異質接面結構製作主動層薄膜。本實驗室合成了四種新穎主鏈施體－受體共聚高分子，PT6TPD、PT8TPD、PCPDTTPD及PDTSTPD，其電子受體皆為噻吩并[3,4-c]吡咯-4,6-二酮（TPD），由於具有堅固、拉電子能力強的共平面雙環結構，讓四種高分子有熱穩定性高、光吸收波段寬廣、HOMO能階足夠深等優點，適合用作太陽能電池之n型材料。 在太陽能電池元件實作上，不同的製程參數及方法對元件之光電轉換效率影響甚鉅。為了易於溶解材料及旋轉塗佈成膜，必須選用適合之溶劑；依最佳的比例混摻P型與N型材料，可形成較平滑的表面形貌；進行熱處理，可讓薄膜內部分子有限度的重新排列以減少電荷陷阱；將PCBM替換為PC71BM與高分子混摻，可望提升在較短波長範圍之光吸收能力；為了讓P型與N型材料有適當的相分離程度，使用添加劑以改善分子排列。 在本實驗中調整以上各項製程參數後，得知四種高分子皆須溶於DCB中，且在90℃下施行退火20分鐘可有最佳表現。而PT6TPD、PT8TPD及PDTSTPD與PC71BM以1:1之比例混摻後，並加入4 vol % DIO可達最佳效率依序為2.56%、2.21%、3.45%；而PCPDTTPD則是以1:4之比例與PC71BM混摻後，再加入3 vol % CN可達最佳效率2.15%。

In this thesis, we fabricated devices with four novel main chain donor -acceptor conjugated polymers, named PT6TPD,PT8TPD,PCPDTTPD, and PDTSTPD. Because of the presence of the electron-deficient thieno[3,4-c]pyrrole-4,6-dione (TPD) moieties, these polymers exhibited an excellent thermal stability, crystalline characteristics, a broad spectral absorption, and a low-lying HOMO energy level—all features that are desirable for solar cell applications. In order to obtain good performance of the solar cells, fabricating methods and parameters have to be processed carefully, including the choice of solvent, the blending composition between polymer and fullerene, the temperature and time of heat treatment, substituting PC71BM over PCBM, and the choice of additive. All the processes could affect the morphology of active layer, and lead to better power conversion efficiency. Modulating the morphologies of the blends allowed us to optimize devices based on these polymer:PC71BM blends. All the optimized blends were dissolved in DCB and annealing at 90℃ for 20 minutes. The solar cell devices prepared by PT6TPD, PT8TPD, and PDTSTPD blended with PC71BM at a ratio of 1:1 and processed with 4 vol% DIO exhibited power conversion efficiency of 2.56%, 2.21%, 3.45%, separately. Another device incorporating PCPDTTPD and PC71BM (blend weight ratio, 1:4), with 3 vol% CN exhibited power conversion efficiency of 2.15%.