Field Effect versus Driving Force: Charge Generation in Small-Molecule Organic Solar Cells
Field Effect versus Driving Force: Charge Generation in Small-Molecule Organic Solar Cells
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DOI：
10.1002/aenm.202002124
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发表时间：
2020-11-09
影响因子：
27.8
通讯作者：
Vandewal, Koen
中科院分区：
文献类型：
--
作者：
Nikolis, Vasileios C.;Dong, Yifan;Vandewal, Koen
在有机半导体中，有效的电荷产生通常需要在电子供体和电子受体之间有一个具有能量梯度的界面，以便解离光产生的激子。然而，基于氯硼亚萘酞菁（SubNc）的单组分有机太阳能电池已经被报道，尽管在与受体的界面上没有能量梯度，但仍能提供相当大的光电流。在这项工作中，它表明，这不是由于直接自由载流子的SubNc照明产生，而是由于特定的器件配置场辅助激子解离机制。随后，该效应在以SubNc为供体的双层有机太阳能电池中的意义得到了证明，表明这种电池中的外部和内部量子效率与供体-受体界面能量学无关。这种以前未探索的机制导致高效率的光电流产生，即使驱动力被最小化，开路电压被最大化。
Efficient charge generation in organic semiconductors usually requires an interface with an energetic gradient between an electron donor and an electron acceptor in order to dissociate the photogenerated excitons. However, single-component organic solar cells based on chloroboron subnaphthalocyanine (SubNc) have been reported to provide considerable photocurrents despite the absence of an energy gradient at the interface with an acceptor. In this work, it is shown that this is not due to direct free carrier generation upon illumination of SubNc, but due to a field-assisted exciton dissociation mechanism specific to the device configuration. Subsequently, the implications of this effect in bilayer organic solar cells with SubNc as the donor are demonstrated, showing that the external and internal quantum efficiencies in such cells are independent of the donor-acceptor interface energetics. This previously unexplored mechanism results in efficient photocurrent generation even though the driving force is minimized and the open-circuit voltage is maximized.