利用量子力學計算探討電子予體─電子受體共軛高分子的結構設計對光電性質的影響

Effects of Structure Design of Donor-Acceptor Conjugated Polymers on Photoelectric Properties via Quantum Mechanical Calculations

李威霆(Wei-Ting Lee)

指導教授 ： 黃慶怡

國立臺灣大學/工學院/高分子科學與工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.10663

摘要

電子予體─電子受體共軛高分子為近年來被廣泛研究的高分子太陽能電池材
料。如何藉由共軛高分子的結構設計來提升光電轉換效率是最重要的議題。共軛
高分子的能階、能隙是影響光電轉換效率的重大因素。因此在本研究中，我們利
用量子力學中的密度泛函理論研究電子予體─電子受體共軛高分子的光電性質。
我們選擇三種電子予體單體fluorene、CPT、BnDT 和三種電子受體單體BT、
DPP、TPD。我們計算這些交替共聚合物的HOMO 能階、LUMO 能階與能隙。
因為BnDT-DPP 的能階與能隙最接近理想值，所以BnDT-DPP 有最大的光電轉換
效率。在共軛高分子中，取代基也是影響能階與能隙的重要因素。我們在聚噻吩
接上推電子基和拉電子基形成交替共聚合物。推電子基包含羥基、胺基和甲氧
基。拉電子基包含氰基、醛基、羧基和硝基。我們發現羥基、甲氧基、氰基和醛
基使分子鏈構形較為共平面，因此OH-CN、OH-CHO、OCH3-CN 和OCH3-CHO
的組合有較低的能隙。最後我們探討取代基的數量和排列方式對共軛高分子的影
響。推電子基與拉電子基的組合會比只有推電子基或只有拉電子基更好。AT-NT
有最低的能隙。

關鍵字

電子予體 ； 電子受體 ； 共軛高分子 ； 能階 ； 能隙 ； 推電子基 ； 拉電子基

並列摘要

Donor-acceptor conjugated polymers are polymer solar cells materials which are
widely researched in recent years. How to promote the power conversion efficiency by
structure design of conjugated polymers is the most important issue. Energy level and
band gap of the conjugated polymers are major factors which affect the power
conversion efficiency. Thus, in this study, we use density functional theory of the
quantum mechanics to investigate the photoelectric properties of the donor-acceptor
conjugated polymers. We choose three donor units, fluorine, CPT, BnDT and three
acceptor units, BT, DPP, TPD.We Calculate the HOMO, LUMO and band gap of these
alternating copolymers. Because the energy level and band gap of BnDT-DPP are the
closest to ideal value, BnDT-DPP has maximum power conversion efficiency. In
conjugated polymers, substituents are also important factors which affect the energy
level and the band gap. We join electron-donating groups and electron-withdrawing
groups to polythiophenes, becoming alternating copolymers. Electron-donating groups
include hydroxy, amino and methoxy groups. Electron-withdrawing groups include
cyano, formyl, carboxyl and nitro groups. We find hydroxy, methoxy, carboxyl and
formyl make the chain conformation coplanar, so the combination of OH-CN, OHCHO,
OCH3-CN and OCH3-CHO have lower band gap. Last, we investigate the effects
of amount and rearrangement of substituents on conjugated polymers. The combination
of electron-donating groups and electron-withdrawing groups is better than only
electron-donating groups or only electron-withdrawing groups. AT-NT has the lowest
band gap.

並列關鍵字

donor ； acceptor ； conjugated polymer ； energy level ； band gap ； electron-donating group ； electron-withdrawing group

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