National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
Department of Physics and State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, 510640, China.
Nat Commun. 2019 Jan 23;10(1):398. doi: 10.1038/s41467-019-08361-4.
The charge separation yield at a bulk heterojunction sets the upper efficiency limit of an organic solar cell. Ultrafast charge transfer processes in polymer/fullerene blends have been intensively studied but much less is known about these processes in all-polymer systems. Here, we show that interfacial charge separation can occur through a polaron pair-derived hole transfer process in all-polymer photovoltaic blends, which is a fundamentally different mechanism compared to the exciton-dominated pathway in the polymer/fullerene blends. By utilizing ultrafast optical measurements, we have clearly identified an ultrafast hole transfer process with a lifetime of about 3 ps mediated by photo-excited polaron pairs which has a markedly high quantum efficiency of about 97%. Spectroscopic data show that excitons act as spectators during the efficient hole transfer process. Our findings suggest an alternative route to improve the efficiency of all-polymer solar devices by manipulating polaron pairs.
在本体异质结中，电荷分离产率设定了有机太阳能电池的最高效率极限。聚合物/富勒烯混合物中的超快电荷转移过程已经得到了深入研究，但对于全聚合物体系中的这些过程，人们知之甚少。在这里，我们表明，在全聚合物光伏混合物中，界面电荷分离可以通过极化子对衍生的空穴转移过程发生，与聚合物/富勒烯混合物中激子主导的途径相比，这是一种根本不同的机制。通过利用超快光学测量，我们已经清楚地识别出一种超快的空穴转移过程，其寿命约为 3 ps，由光激发的极化子对介导，具有约 97%的显著高量子效率。光谱数据表明，激子在有效的空穴转移过程中充当旁观者。我们的发现表明，通过操纵极化子对，为提高全聚合物太阳能电池的效率提供了一种替代途径。
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