Limitations of Charge Transfer State Parameterization Using Photovoltaic External Quantum Efficiency
Limitations of Charge Transfer State Parameterization Using Photovoltaic External Quantum Efficiency
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DOI：
10.1002/aenm.202001828
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发表时间：
2020-09-22
影响因子：
27.8
通讯作者：
Meredith, Paul
中科院分区：
文献类型：
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作者：
Armin, Ardalan;Zarrabi, Nasim;Meredith, Paul
在由受体和施主有机半导体混合物组成的体异质结太阳能电池中，自由载流子的光产生通过分子间电荷转移（CT）状态进行。非绝热马库斯理论已被证明可以有效地解释这些子隙态的吸收和发射，这些子隙态具有极弱的发射概率和吸收截面，使得它们难以用光学光谱直接探测。因此，Marcus模型中涉及的CT状态参数通常是从光伏外量子效率（EQE(PV)）和电致发光的配件中提取的。这两个光谱（在理想情况下）通过所谓的互易原理相互关联。在本文中，证明了这种方法的局限性，特别是简单的低精细腔干涉效应作为不均匀光谱滤波器对发射和吸收的影响。这可能产生几乎虚假的CT状态参数化，例如，从meqe （PV）获得的吸收系数的相对误差高达90%。它显示了如何使用应用于eqe （PV）的迭代传递矩阵方法部分解除这些限制。
Free carrier photogeneration in bulk-heterojunction solar cells composed of blends of acceptor and donor organic semiconductors proceeds via intermolecular charge transfer (CT) states. Non-adiabatic Marcus theory has proven valid to explain the absorption and emission of these sub-gap states which have extremely weak emission probabilities and absorption cross sections making them difficult to probe directly using optical spectroscopy. Therefore, the CT state parameters involved in the Marcus model are often extracted from fittings on the photovoltaic external quantum efficiency (EQE(PV)) and electroluminescence. These two spectra are (ideally) interrelated via the so-called reciprocity principle. In this paper, the limitations of such an approach are demonstrated, in particular the impact of simple low finesse cavity interference effects acting as an uneven spectral filter for emission and absorption. This can produce almost spurious CT state parameterization with, for example, relative errors as large as 90% in absorption coefficients obtained fromEQE(PV). It is shown how these limitations can be partially lifted using an iterative transfer matrix approach applied to theEQE(PV).