Spectroscopic investigation of excitons, photocarriers, and bias-induced carriers in regioregular poly(3-alkylthiophene)
Spectroscopic investigation of excitons, photocarriers, and bias-induced carriers in regioregular poly(3-alkylthiophene)
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DOI：
10.1103/physrevb.83.205203
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发表时间：
2011-05-18
影响因子：
3.7
通讯作者：
Hashimoto, Hideki
中科院分区：
文献类型：
--
作者：
Kanemoto, Katsuichi;Yasui, Motoaki;Hashimoto, Hideki
利用连续波（cw-）和飞秒（fs-）瞬态光诱导吸收（PIA）和器件调制（DM）光谱等多种光谱技术研究了区域规则聚（3-烷基噻吩）（P3 AT）薄膜中的激子、光生载流子和偏压诱导载流子。聚（3-己基噻吩）（P3 HT）薄膜的连续波PIA和DM光谱之间的比较表明，由连续波光激发产生的光载流子主要由局域极化子，而电荷注入主要产生离域极化子。光激发强度依赖的cw PIA信号表明，本地化和离域光生极化子服从cw光激发下的双分子复合过程。通过比较DM和cw PIA光谱的强度，估计P3 HT薄膜中cw光激发产生的极化子比例为1/（1+0.137 I（1/2））（I（mW/cm（2）。DM光谱表明，本地化和离域极化子迅速增加的偏置电流的上升点。P3 AT膜的顺时针PIA漂白光谱随P3 AT的烷基侧链长度而变化，并且几乎可以用单一的Huang-Rhys因子再现。计算得到的Huang-Rhys因子表明，随着P3 AT薄膜层间距的增大，激子最终迁移点的电声耦合增强，表明层间耦合影响二维层内激子迁移点的电声耦合.
Excitons, photocarriers, and bias-induced carriers in regioregular poly(3-alkylthiophene) (P3AT) films were investigated using a variety of spectroscopic techniques, such as continuous-wave- (cw-) and femtosecond (fs-) transient photoinduced absorption (PIA) and device modulation (DM) spectroscopies. Comparison between the cw PIA and DM spectra of the poly(3-hexylthiophene) (P3HT) film reveals that photocarriers generated by cw photoexcitation are dominated by localized polarons, whereas charge injection primarily creates delocalized polarons. The photoexcitation intensity dependence of the cw PIA signals demonstrates that both localized and delocalized photogenerated polarons obey a bimolecular recombination process under cw photoexcitation. The proportion of polarons generated by cw photoexcitation in the P3HT film is estimated to be 1/(1+0.137 I(1/2)) for I (mW/cm(2)) by comparison of the spectral intensities between the DM and cw PIA spectra. DM spectroscopy reveals that both localized and delocalized polarons rapidly increase at a rise point of the bias current. The cw PIA bleaching spectra of P3AT films are shown to vary with the length of the alkyl sidechains of P3AT and be almost reproduced using a single Huang-Rhys factor. The Huang-Rhys factors obtained reveal a trend that the electron-phonon couplings of final exciton migration sites become strong with the increase in the interlamella distance in the P3AT film, which indicates that interlamella couplings affect the electron-phonon couplings of the migration sites located at two-dimensional lamellas.