Counterion Control and the Spectral Signatures of Polarons, Coupled Polarons, and Bipolarons in Doped P3HT Films
Counterion Control and the Spectral Signatures of Polarons, Coupled Polarons, and Bipolarons in Doped P3HT Films
复制标题
DOI：
10.1002/adfm.202213652
复制
发表时间：
2023-02
影响因子：
19
通讯作者：
Eric C Wu;Charlene Z. Salamat;O. Ruiz;Thomas Qu;Alexis Kim;S. Tolbert;B. J. Schwartz
中科院分区：
文献类型：
--
作者：
Eric C Wu;Charlene Z. Salamat;O. Ruiz;Thomas Qu;Alexis Kim;S. Tolbert;B. J. Schwartz
当一个电子从共轭聚合物(如聚（3 -己基噻吩- 2,5 -二基）（P3HT）上移除时，剩余的空穴和相关的聚合物主结构从芳香型到奎风型的变化被称为极化子。双极化子是通过从已经氧化的聚合物段中去除未配对的电子而产生的。在电化学掺杂的P3HT薄膜中，极化子和双极化子很容易被观察到，但在化学掺杂的P3HT薄膜中，双极化子很少形成。利用光谱和X射线衍射实验以及随时间变化的密度泛函理论计算，研究了反离子位置对极化子、强耦合极化子和双极化子形成的影响，从而解释了这一点。对偶位置控制着两个极化子是否自旋对形成双极化子，或者它们是否在没有自旋对的情况下强耦合。当两个反离子靠近同一聚合物段时，可以形成双极化子，其吸收光谱与单极化子的吸收光谱发生蓝移。否则，高浓度的极化子不会自旋对，而是J偶，导致吸收光谱红移。双极化子形成所需的反离子位置伴随着聚合物结晶度的丧失。这些结果解释了在电化学和化学掺杂共轭聚合物中观察到的单极化子、耦合单极化子和单线态双极化子的形成顺序。
When an electron is removed from a conjugated polymer, such as poly(3‐hexylthiophene‐2,5‐diyl) (P3HT), the remaining hole and associated change in the polymer backbone structure from aromatic to quinoidal are referred to as a polaron. Bipolarons are created by removing the unpaired electron from an already‐oxidized polymer segment. In electrochemically‐doped P3HT films, polarons, and bipolarons are readily observed, but in chemically‐doped P3HT films, bipolarons rarely form. This is explained by studying the effects of counterion position on the formation of polarons, strongly coupled polarons, and bipolarons using both spectroscopic and X‐ray diffraction experiments and time‐dependent density functional theory calculations. The counterion positions control whether two polarons spin‐pair to form a bipolaron or whether they strongly couple without spin‐pairing are found. When two counterions lie close to the same polymer segment, bipolarons can form, with an absorption spectrum that is blueshifted from that of a single polaron. Otherwise, polarons at high concentrations do not spin‐pair, but instead J‐couple, leading to a redshifted absorption spectrum. The counterion location needed for bipolaron formation is accompanied by a loss of polymer crystallinity. These results explain the observed formation order of single polarons, coupled single polarons, and singlet bipolarons in electrochemically‐ and chemically‐doped conjugated polymers.