Department of Materials Science and Engineering and ‡Department of Physics, The University of Texas at Dallas , Richardson, Texas 75080, United States.
Nano Lett. 2015 Nov 11;15(11):7627-32. doi: 10.1021/acs.nanolett.5b03473. Epub 2015 Oct 14.
Substrates can significantly affect the electronic properties of organic semiconductors. In this paper, we report the effects of contact-induced doping, arising from charge transfer between a high work function hole extraction layer (HEL) and the organic active layer, on organic photovoltaic device performance. Employing a high work function HEL is found to increase doping in the active layer and decrease photocurrent. Combined experimental and modeling investigations reveal that higher doping increases polaron-exciton quenching and carrier recombination within the field-free region. Consequently, there exists an optimal HEL work function that enables a large built-in field while keeping the active layer doping low. This value is found to be ~0.4 eV larger than the pinning level of the active layer material. These understandings establish a criterion for optimal design of the HEL when adapting a new active layer system and can shed light on optimizing performance in other organic electronic devices.
基底会显著影响有机半导体的电子性质。在本文中，我们报告了接触诱导掺杂对有机光伏器件性能的影响，这种掺杂是由高功函数空穴萃取层（HEL）与有机活性层之间的电荷转移引起的。我们发现，采用高功函数 HEL 会增加活性层中的掺杂，从而降低光电流。实验和模拟研究的结合揭示了较高的掺杂会增加无场区域内极化子-激子猝灭和载流子复合。因此，存在一个最佳的 HEL 功函数，它可以在保持活性层掺杂较低的情况下产生大的内置电场。这个值被发现比活性层材料的钉扎能级大约 0.4eV。这些理解为适应新的活性层系统时最佳设计 HEL 提供了一个标准，并可以为其他有机电子器件的性能优化提供启示。
