Tailored Interface Energetics for Efficient Charge Separation in Metal Oxide-Polymer Solar Cells
Tailored Interface Energetics for Efficient Charge Separation in Metal Oxide-Polymer Solar Cells
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DOI：
10.1038/s41598-018-36271-w
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发表时间：
2019-01-11
影响因子：
4.6
通讯作者：
Schmidt-Mende, Lukas
中科院分区：
文献类型：
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作者：
Ehrenreich, Philipp;Groh, Arthur;Schmidt-Mende, Lukas
太阳能电池中有机-无机杂化界面存在电荷分离效率低的问题，但其性能限制的原因尚不清楚。在这项工作中，我们重点研究了金属氧化物-聚合物界面能量学在电荷产生过程中的作用。为此，我们提出了基于苯并噻唑的新型噻吩低聚物，该低聚物系统地调整了无机受体TiO2的表面能量学。在一个简单的双分子层结构中，我们用给体聚合物聚（3-己基噻吩）（P3HT），我们能够大大改善电荷的产生过程。通过结合超快宽带瞬态吸收光谱对太阳能电池器件的电子表征，我们证明了这种显著的性能改进源于局域电荷转移态的重组减少。在此背景下，揭示了有助于有机-无机界面电荷分离的中间层的基本设计规则。除了作为电子和空穴之间的物理间隔，中间层应该提供(1)一个大的能量偏移来驱动激子解离，(2)一个推拉构建块来降低电荷转移态的库仑结合能，(3)一个能量级联来限制载流子向界面的反向扩散。
Hybrid organic-inorganic heterointerfaces in solar cells suffer from inefficient charge separation yet the origin of performance limitations are widely unknown. In this work, we focus on the role of metal oxide-polymer interface energetics in a charge generation process. For this purpose, we present novel benzothiadiazole based thiophene oligomers that tailor the surface energetics of the inorganic acceptor TiO2 systematically. In a simple bilayer structure with the donor polymer poly(3-hexylthiophene) (P3HT), we are able to improve the charge generation process considerably. By means of an electronic characterization of solar cell devices in combination with ultrafast broadband transient absorption spectroscopy, we demonstrate that this remarkable improvement in performance originates from reduced recombination of localized charge transfer states. In this context, fundamental design rules for interlayers are revealed, which assist the charge separation at organic-inorganic interfaces. Beside acting as a physical spacer in between electrons and holes, interlayers should offer (1) a large energy offset to drive exciton dissociation, (2) a push-pull building block to reduce the Coulomb binding energy of charge transfer states and (3) an energy cascade to limit carrier back diffusion towards the interface.