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Ultrafast Charge Dynamics in Dilute-Donor versus Highly Intermixed TAPC:C60 Organic Solar Cell Blends.
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2020-06-22 , DOI: 10.1021/acs.jpclett.0c01495
Gareth John Moore 1 , Martina Causa' 1 , Josue F Martinez Hardigree 2 , Safakath Karuthedath 3 , Ivan Ramirez 2 , Anna Jungbluth 2 , Frédéric Laquai 3 , Moritz Riede 2 , Natalie Banerji 1
Affiliation  

Elucidating the interplay between film morphology, photophysics, and device performance of bulk heterojunction (BHJ) organic photovoltaics remains challenging. Here, we use the well-defined morphology of vapor-deposited di-[4-(N,N-di-p-tolyl-amino)-phenyl]cyclohexane (TAPC):C60 blends to address charge generation and recombination by transient ultrafast spectroscopy. We gain relevant new insights to the functioning of dilute-donor (5% TAPC) fullerene-based BHJs compared to molecularly intermixed systems (50% TAPC). First, we show that intermolecular charge-transfer (CT) excitons in the C60 clusters of dilute BHJs rapidly localize to Frenkel excitons prior to dissociating at the donor:acceptor interface. Thus, both Frenkel and CT excitons generate photocurrent over the entire fullerene absorption range. Second, we selectively monitor interfacial and bulk C60 clusters via their electro-absorption, demonstrating an energetic gradient that assists free charge generation. Third, we identify a fast (<1 ns) recombination channel, whereby free electrons recombine with trapped holes on isolated TAPC molecules. This can harm the performance of dilute solar cells, unless the electrons are rapidly extracted in efficient devices.

中文翻译:

稀释供体与高度混合的TAPC:C60有机太阳能电池混合物的超快充电动力学。

阐明薄膜形态,光物理和本体异质结(BHJ)有机光伏器件性能之间的相互作用仍然是一项挑战。在这里,我们使用汽相沉积的二[4-(NN-二-甲苯基氨基)-苯基]环己烷(TAPC):C 60共混物的良好形态来解决电荷的产生和瞬态重组超快光谱。与分子混合系统(50%TAPC)相比,我们获得了有关基于稀释供体(5%TAPC)富勒烯的BHJs功能的相关新见解。首先,我们证明了C 60中的分子间电荷转移(CT)激子稀的BHJ簇在供体:受体界面解离之前迅速定位于Frenkel激子。因此,Frenkel和CT激子都在整个富勒烯吸收范围内产生光电流。其次,我们通过电吸收选择性地监测界面C 60簇和整体C 60簇,证明了有助于自由电荷产生的高能梯度。第三,我们确定了一个快速(<1 ns)的重组通道,由此自由电子与孤立的TAPC分子上的陷阱空穴重组。除非在有效的设备中迅速提取电子,否则这可能会损害稀薄太阳能电池的性能。
更新日期:2020-07-16
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