Effects of Structure Design of Donor-Acceptor Conjugated Polymers on Photoelectric Properties via Quantum Mechanical Calculations
Date Issued
2015
Date
2015
Author(s)
Lee, Wei-Ting
Abstract
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.
Subjects
donor
acceptor
conjugated polymer
energy level
band gap
electron-donating group
electron-withdrawing group
Type
thesis