Intercalated vs Nonintercalated Morphologies in Donor-Acceptor Bulk Heterojunction Solar Cells: PBTTT:Fullerene Charge Generation and Recombination Revisited.
Intercalated vs Nonintercalated Morphologies in Donor-Acceptor Bulk Heterojunction Solar Cells: PBTTT:Fullerene Charge Generation and Recombination Revisited.
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供体-受体体异质结太阳能电池中的插层与非插层形态：PBTTT：富勒烯电荷产生和重组重新审视
DOI：
10.1021/acs.jpclett.7b01571
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Durrant
中科院分区：
文献类型：
--
作者：
Collado-Fregoso;Shoaee;Schroeder;Mcculloch;Kassal;Durrant
在这篇论文中，我们使用PBTTT和两种不同的富勒烯衍生物（PC70BM和ICTA）的混合物分别作为插层和非插层形貌模型，研究了在有机光伏器件和共混薄膜中，供体：受体界面纳米结构在电荷分离和重组中的作用。热力学模拟表明，完全插层体系具有较大的电荷分离自由能势垒，而非插层体系的自由能势垒明显较低，当模型中包含能量无序时，自由能势垒几乎消失。尽管存在这些差异，但飞秒分辨瞬态吸收光谱（TAS）和延时收集场（TDCF）在两个系统中都表现出广泛的一阶损失，这表明双极对是光激发的主要产物。相比之下，由完全嵌入的聚合物：富勒烯区域和富勒烯聚集域（1:4 PBTTT:PC70BM）组成的系统是唯一一个显示出缓慢的二阶自由电荷重组的系统，导致器件具有更高的短路电流和填充因子。因此，这项研究为界面纳米结构的作用和束缚电荷的性质及其对电荷产生和重组的影响提供了新的考虑。
In this Letter, we study the role of the donor:acceptor interface nanostructure upon charge separation and recombination in organic photovoltaic devices and blend films, using mixtures of PBTTT and two different fullerene derivatives (PC70BM and ICTA) as models for intercalated and nonintercalated morphologies, respectively. Thermodynamic simulations show that while the completely intercalated system exhibits a large free-energy barrier for charge separation, this barrier is significantly lower in the nonintercalated system and almost vanishes when energetic disorder is included in the model. Despite these differences, both femtosecond-resolved transient absorption spectroscopy (TAS) and time-delayed collection field (TDCF) exhibit extensive first-order losses in both systems, suggesting that geminate pairs are the primary product of photoexcitation. In contrast, the system that comprises a combination of fully intercalated polymer:fullerene areas and fullerene-aggregated domains (1:4 PBTTT:PC70BM) is the only one that shows slow, second-order recombination of free charges, resulting in devices with an overall higher short-circuit current and fill factor. This study therefore provides a novel consideration of the role of the interfacial nanostructure and the nature of bound charges and their impact upon charge generation and recombination.
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