高導電度富勒烯與交聯富勒烯應用於反式高分子太陽能電池之界面層研究

Abstract

本研究致力於改善交聯式碳六十衍生物－含兩個可熱交聯苯乙烯基團樹枝狀碳六十聚合物（PCBSD）的導電度與電子遷移率。使用摻雜的方式，導入另一高導電度之離子性富勒烯－碘化富勒吡咯烷（FPI）。經由摻雜後，可改善原先交聯性富勒烯材料導電度與電子遷移率過低的問題。在有機場效電晶體元件上測量其導電度與電子遷移率，發現皆可上升2個數量級，且混摻離子性富勒烯後仍然保持原先交聯高分子抗溶劑等優點。 而將此材料應用於反式高分子太陽能電池上，作為氧化鋅表面修飾層，可提供額外的電子電洞對解離界面，且由於增加了薄膜的導電度，故可以降低元件之串聯電阻，進而提升高分子太陽能電池元件的短路電流與光電轉換效率。本研究共使用三種共軛高分子－PDBTTT-C-T、P3HT、和PTh4FBT-PorCN作為吸光材料，在元件的效率表現上，使用此複合材料做為氧化鋅修飾層均能看到效率的提升。然而發現元件的漏電流有上升的情況，而使用循環伏安法量測FPI的能階，發現FPI的LUMO能階較低，故電子再經過此界面層時與高分子的電洞複合機率較高，可能為漏電流上升主因。 本實驗最後將C-PCBSD與FPI應用於主動層之受體材料，並製作含奈米柱陣列結構之有序異質接面結構元件，發現當混摻高導電度富勒烯－FPI後，由於提升了受體的電子遷移率與導電度，可降低元件的串聯電阻。在PBDTTT-C-T：PC71BM為主動層的元件上，可將短路電流從0.78 mA/cm2提升至1.06 mA/cm2，填充因子從27.9 %提升至43.7 %，而由於混摻FPI會導致元件的漏電流增加，故開路電壓從0.85 V降至0.66 V，元件的光電轉換效率由0.18 %上升至0.33 %，提升幅度達1.8倍。

The research is aimed to improve the conductivity and electron mobility of the cross-linkable fullerene derivatives, i.e., [6,6]-phenyl-C61-butyric styryl dendron ester (PCBSD) by adding anthor highly conducting of ionic fullerene – Fulleropyrroidinium iodide (FPI) as a dopant. Addition of FPI in PCBSD can solve the problem of low conductivity and electron mobility in cross-linked fullerene network. The results demonstrate that the conductivity of the fullerene film increases and the electron mobility of an OFET device increase two orders of magnitude. The solvent-resistance property of the obtained cross-linked network is kept after doping with FPI. This material is used as an interfacial layer to modify the surface of zinc oxide in the inverted polymer solar cells. This layer provide additional electron-hole pair dissociation interface and reduce series resistance of the device because the conductivity of the film increases, and therefore the short-circuit current and the power conversion efficiency of the polymer solar cell increases. We fabricate the inverted solar cells by using three kinds of conjugated polymers, i.e., PBDTTT-C-T, P3HT, and PTh4FBT-PorCN. The results show that the power conversion efficiencies of the solar cells with this interfacial layer are enhanced. However, we found that the leakage current of these solar cells are also increased. The reason is because that FPI’s LUMO energy level is lower than that of PCBSD. When electrons pass through this interface, the probability of the charge recombination is higher than that of PCBSD without doping FPI. This is the reason for the increasing in leakage current. Finally, we used the mixture of C-PCBSD and FPI dopant to fabricate the crosslinked fullerene nano-rod to form the polymer solar cells with ordered heterojunction structure with PBDTTT-C-T as a donor. For comparison purpose, we fabricate a similar device with C-PCBSD nano-rod. The results show that the device with FPI dopant has better performance. It’s short-circuit current increases from 0.78 mA/cm2 to 1.06 mA/cm2.It’s fill factor increases from 27.9 % to 43.7 %. However, it’s open circuit voltage drops from 0.85 V to 0.66 V. This could be due to the increasing in leakage current. Overall the power conversion efficiency of the device increases from 0.18 % to 0.33 %, and it increases about 1.8 times.