吲哚咔唑共軛高分子之合成與鑑定及其在太陽能電池之應用

Abstract

本研究總共合成了六個共軛高分子，C8IC-C8DPP、C8IC-EHDPP、C8IC-BHDT、EHIC-C8DPP、EHIC-EHDPP、以及EHIC-BHDT。這些共軛高分子以Indolocarbazole為主體，並在其上分別導入辛烷鏈及2-乙基己烷鏈，再搭配不同的電子受體BHDT和不同長碳鏈的DPP，利用Suzuki coupling進行聚合反應，得到六個共軛高分子材料。 吸收光譜方面，BHDT系列的吸收範圍從到400 - 700nm，其能隙為2.04 eV；DPP系列共軛高分子則落在到400 - 900nm，能隙在1.55 – 1.59 eV之間。在熱穩定性方面，所有材料的熱裂解溫度在400 ~ 430oC之間，具有不錯的熱穩定性。在材料的能階方面，BHDT系列共軛高分子的HOMO能階比DPP系列共軛高分子來的低，但由於BHDT系列能隙較高，共軛高分子的LUMO位置相對較高。將這些共軛高分子材料製作成Bulk Heterojunctuion (BHJ) 太陽能電池的形式，其元件結構為：ITO/PEDOT:PSS/Polymer:PC60BM(1:2, w/w)/Ca/Al。其中EHIC-EHDPP因為高分子成膜後相分離明顯，沒有明顯的光電轉換效率。而EHIC-C8DPP共軛高分子在製程上成膜性較好，元件表現也最好，Voc為0.52 V，Jsc為4.03 mA/cm2，fillfactor為0.34，光電轉換效率為0.73%。

In this study, six conjugated polymers, i.e., C8IC-C8DPP, C8IC-EHDPP, C8IC-BHDT, EHIC-C8DPP, EHIC-EHDPP, and EHIC-BHDT were synthesized and characterized. All polymers consist of indolocarbazole unit which has two different alkyl chains. Two kinds of electron acceptor units, i.e., BHDT and DPP were polymerized with indolocarbazole unit via Suzuki coupling to obtain these polymers. The absorption spectra of BHDT series cover from 400 to 700 nm, the optical band gaps are around 2.04eV. The absorption spectra of DPP series cover from 400 to 900 nm, and their optical band gaps range from 1.55 to 1.59 eV. The decomposition temperatures (Td) of all conjugated polymers range from 400 to 430 oC, indicating their excellent thermal stabilities. The HOMO levels of BHDT-based conjugated polymers are more low-lying than those of DPP-based polymers. Due to the larger band gaps, the BHDT series have higher LUMO levels. We used these conjugated polymers to fabricate the bulk heterojunction (BHJ) solar cell devices with the configuration of ITO/PEDOT:PSS/Polymer:PC60BM(1:2, w/w)/Ca/Al. Due to the worse film quality under device fabrication, polymer of EHIC-EHDPP was not observed visible PCE values. Polymer EHIC-C8DPP showed the best film quality, and had the best PCE of 0.73% with a Voc of 0.52 V, a Jsc of 4.03 mA/cm2, and a fillfactor of 0.34.