Electronic Structure and Geminate Pair Energetics at Organic–Organic Interfaces: The Case of Pentacene/C60 Heterojunctions
Electronic Structure and Geminate Pair Energetics at Organic–Organic Interfaces: The Case of Pentacene/C60 Heterojunctions
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DOI：
10.1002/adfm.200901233
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发表时间：
2009-12
影响因子：
19
通讯作者：
S. Verlaak;D. Beljonne;D. Cheyns;C. Rolin;M. Linares;F. Castet;J. Cornil;P. Heremans
中科院分区：
文献类型：
--
作者：
S. Verlaak;D. Beljonne;D. Cheyns;C. Rolin;M. Linares;F. Castet;J. Cornil;P. Heremans
有机半导体的特征在于局域态，其能量主要由与其直接分子环境的静电相互作用决定。因此，不同有机半导体之间异质结的能量景观的细节不能简单地从单个半导体的能量景观中推断出来，而且到目前为止，它们在很大程度上仍未被探索。在这里，微静电计算进行澄清的电子结构的性质和双生对能量在并五苯/C60接口，作为原型的供体分子和富勒烯电子受体之间的接口。分子四极矩的大小和方向，由材料选择，晶体取向，和半导体的热力学生长参数决定，占主导地位的界面能量。四极子不仅与电荷载流子产生直接的静电相互作用，而且，此外，四极子场在界面处的不连续性引起永久的界面偶极子。这种不连续性对于具有C60分子的界面特别引人注目，由于其对称性，C60分子不具有四极。因此，在并五苯/C60界面处，真空能级位移和成对解离都严重依赖于并五苯π系统相对于相邻C60的取向。
Organic semiconductors are characterized by localized states whose energies are predominantly determined by electrostatic interactions with their immediate molecular environment. As a result, the details of the energy landscape at heterojunctions between different organic semiconductors cannot simply be deduced from those of the individual semiconductors, and they have so far remained largely unexplored. Here, microelectrostatic computations are performed to clarify the nature of the electronic structure and geminate pair energetics at the pentacene/C60 interface, as archetype for an interface between a donor molecule and a fullerene electron acceptor. The size and orientation of the molecular quadrupole moments, determined by material choice, crystal orientation, and thermodynamic growth parameters of the semiconductors, dominate the interface energetics. Not only do quadrupoles produce direct electrostatic interactions with charge carriers, but, in addition, the discontinuity of the quadrupole field at the interface induces permanent interface dipoles. That discontinuity is particularly striking for an interface with C60 molecules, which by virtue of their symmetry possess no quadrupole. Consequently, at a pentacene/C60 interface, both the vacuum‐level shift and geminate pair dissociation critically depend on the orientation of the pentacene π‐system relative to the adjacent C60.