研究目的
To study the charge transport properties of PTB7 and PTB7-Th polymers, focusing on the influence of pendant groups on mobility and reorganization energy.
研究成果
The field-effect mobility of PTB7-Th is approximately 10 times higher than that of PTB7, attributed to a lower reorganization energy due to the thiophene pendant group increasing molecular rigidity. This provides insights into how pendant groups influence charge transport in conjugated polymers without altering the backbone.
研究不足
The study focuses on specific polymers (PTB7 and PTB7-Th) and may not generalize to other materials. Computational methods rely on approximations in density functional theory. Experimental measurements are subject to device fabrication variations and environmental conditions.
1：Experimental Design and Method Selection:
The study involves fabricating organic field-effect transistors (OFETs) and bulk-heterojunction (BHJ) devices to measure field-effect mobility and reorganization energy. Computational methods using first-principles calculations (VASP with PAW-PBE functional) are employed to calculate reorganization energy and analyze molecular structures.
2：Sample Selection and Data Sources:
Polymers PTB7 and PTB7-Th are used as samples, with identical backbones but differing pendant groups. Devices are fabricated on silicon and ITO-coated glass substrates.
3：List of Experimental Equipment and Materials:
Equipment includes spin coaters, thermal evaporators, semiprobe station with Keithly 4200 system, ellipsometer, and computational resources (VASP software). Materials include PTB7, PTB7-Th, PC71BM, PMMA, MoO3, Ag, Au, PEDOT:PSS, chlorobenzene, 1,8-diiodooctane, and substrates.
4：Experimental Procedures and Operational Workflow:
For OFETs, substrates are prepared with dielectric layers, polymers are spin-coated, and electrodes are deposited via thermal evaporation. Electrical measurements are conducted in a nitrogen environment. For BHJ devices, blends with PC71BM are spin-coated, and electrodes are evaporated. Computational geometry optimizations and reorganization energy calculations are performed using VASP.
5：Data Analysis Methods:
Field-effect mobility is extracted from transfer characteristics using standard equations. Reorganization energy is calculated from first-principles and verified using EQE measurements of BHJ devices. Marcus theory is applied to analyze charge hopping rates.
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