Understanding of charge carrier dynamics on a picosecond time scale is very important for generation and relaxation of charge carriers in organic photovoltaic solar cells. Here, we study the dynamics of photogenerated charge carriers of diketopyrrolopyrrole-linked tetrabenzoporphyrin (C4-DPP-BP) bulk heterojunction (BHJ) thin films mixed with [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) by subpicosecond time-resolved terahertz (THz) spectroscopy. For the excitation at 800 nm, the decay time constants of the time-resolved THz signals are 0.5 ps and 14 ps that result from the relaxation of bound polaron pair. Furthermore, the results reveal that the amplitude of the subpicosecond decay in the time-resolved THz signal is sensitive to the fluence of the optical excitation pulse. It is considered that this decaying component at higher fluence originates from polaron pair annihilation. We also discuss the difference in carrier dynamics between neat C4-DPP-BP and the C4-DPP-BP based BHJ thin films to understand dynamic behavior of the local charge carriers.

皮秒级的电荷载流子动力学的理解对于有机光伏太阳能电池中电荷载流子的产生和松弛非常重要。在这里，我们研究与[6,6]-苯基-C _61-丁酸甲酯（PC ₆₁）混合的二酮基吡咯并吡咯连接的四苯并卟啉（C4-DPP-BP）本体异质结（BHJ）薄膜的光生电荷载体的动力学。亚皮秒时间分辨太赫兹（THz）光谱。对于在800 nm处的激发，时间分辨的THz信号的衰减时间常数分别为0.5 ps和14 ps，这是由于束缚极化子对的弛豫而引起的。此外，结果表明，时间分辨的THz信号中的亚皮秒衰减幅度对光激发脉冲的能量密度敏感。可以认为，该高通量的衰变成分起因于极化子对an灭。我们还讨论了纯C4-DPP-BP和基于C4-DPP-BP的BHJ薄膜在载流子动力学方面的差异，以了解局部电荷载流子的动态行为。