Solution Phase Exciton Diffusion Dynamics of a Charge-Transfer Copolymer PTB7 and a Homopolymer P3HT

被引:25
作者
Cho, Sung [1 ,2 ,3 ,4 ]
Rolczynski, Brian S. [1 ,2 ,3 ]
Xu, Tao [5 ,6 ]
Yu, Luping [5 ,6 ]
Chen, Lin X. [1 ,2 ,3 ]
机构
[1] Argonne Natl Lab, Chem Sci & Engn Div, Argonne, IL 60439 USA
[2] Northwestern Univ, ANSER Ctr, Evanston, IL 60208 USA
[3] Northwestern Univ, Dept Chem, Evanston, IL 60208 USA
[4] Chonnam Natl Univ, Dept Chem, Gwangju 500757, South Korea
[5] Univ Chicago, Dept Chem, Chicago, IL 60637 USA
[6] Univ Chicago, James Franck Inst, Chicago, IL 60637 USA
基金
新加坡国家研究基金会;
关键词
CONJUGATED POLYMERS; ENERGY MIGRATION; POLYTHIOPHENE; FLUORESCENCE; RELAXATION; GENERATION; EFFICIENCY; CONVERSION; CELLS;
D O I
10.1021/jp5111345
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Using ultrafast polarization-controlled transient absorption (TA) measurements, dynamics of the initial exciton states were investigated on the time scale of tens of femtoseconds to about 80 ps in two different types of conjugated polymers extensively used in active layers of organic photovoltaic devices. These polymers are poly(3-fluorothienothiophenebenzodithiophene) (PTB7) and poly-3-hexylthiophene (P3HT), which are charge-transfer polymers and homopolymers, respectively. In PTB7, the initial excitons with excess vibrational energy display two observable ultrafast time constants, corresponding to coherent exciton diffusion before the vibrational relaxation, and followed by incoherent exciton diffusion processes to a neighboring local state after the vibrational relaxation. In contrast, P3HT shows only one exciton diffusion or conformational motion time constant of 34 ps, even though its exciton decay kinetics are multiexponential. Based on the experimental results, an exciton dynamics mechanism is conceived taking into account the excitation energy and structural dependence in coherent and incoherent exciton diffusion processes, as well as other possible deactivation processes including the formation of the pseudo-charge-transfer and charge separate states, as well as interchain exciton hopping or coherent diffusion.
引用
收藏
页码:7447 / 7456
页数:10
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