Reconciling the Driving Force and the Barrier to Charge Separation in Donor–Nonfullerene Acceptor Films,ACS Energy Letters

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Reconciling the Driving Force and the Barrier to Charge Separation in Donor–Nonfullerene Acceptor Films
ACS Energy Letters ( IF 19.3 ) Pub Date : 2021-09-15 , DOI: 10.1021/acsenergylett.1c01563
Taylor G. Allen ₁ , Panagiota Kafourou ₂ , Bryon W. Larson ₁ , Martin Heeney ₂ , Obadiah G. Reid _{1,

3} , Garry Rumbles _{1,

3}

Affiliation

We investigate the dependence of charge yields on the driving force for photoinduced electron transfer in a series of all-small-molecule, semiconducting films made from indacenodithiophene nonfullerene acceptors (IDT NFAs). In contrast to reports of efficient, barrierless charge separation at near zero driving force for NFA-containing organic photovoltaics, we find that barrierless charge separation occurs only if the driving force is sufficient to overcome the Coulomb potential, ≥300 meV, based on time-resolved microwave conductivity and PL quenching measurements of 5 mmolal sensitized and 700 mmolal blended films comprising IDT NFAs paired with three different donors. This discrepancy with recent literature is caused by a difference in the way that we calculate driving force. Far from being semantic, the driving force calculation is crucial because its value controls the mechanisms needed to explain experimental observations. We provide a candid assessment of the uncertainties for our methods and popular ones used in the literature and emphasize the importance of standardizing methods across this field.

中文翻译：

调和供体-非富勒烯受体薄膜中的驱动力和电荷分离障碍

我们研究了电荷产率对一系列由茚二噻吩非富勒烯受体 (IDT NFA) 制成的全小分子半导体薄膜中光致电子转移驱动力的依赖性。与关于含 NFA 的有机光伏电池在接近零驱动力下的高效、无障碍电荷分离的报道相反，我们发现只有当驱动力足以克服库仑电位时才会发生无障碍电荷分离，≥300 meV，基于时间-对包含 IDT NFA 和三种不同供体的 5 毫摩尔敏化膜和 700 毫摩尔混合膜的分辨微波电导率和 PL 猝灭测量。这种与最近文献的差异是由我们计算驱动力的方式不同造成的。远非语义，驱动力计算至关重要，因为它的值控制了解释实验观察所需的机制。我们对我们的方法和文献中使用的流行方法的不确定性进行了坦率的评估，并强调了跨该领域标准化方法的重要性。

更新日期：2021-10-08

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