Dissociation of Charge Transfer States and Carrier Separation in Bilayer Organic Solar Cells: A Time-Resolved Electroabsorption Spectroscopy Study,Journal of the American Chemical Society

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Dissociation of Charge Transfer States and Carrier Separation in Bilayer Organic Solar Cells: A Time-Resolved Electroabsorption Spectroscopy Study
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2015-06-19 , DOI: 10.1021/jacs.5b03682
Andrius Devižis ₁ , Jelissa De Jonghe-Risse , Roland Hany ₂ , Frank Nüesch ₂ , Sandra Jenatsch ₂ , Vidmantas Gulbinas ₁ , Jacques-E. Moser

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Ultrafast optical probing of the electric field by means of Stark effect in planar heterojunction cyanine dye/fullerene organic solar cells enables one to directly monitor the dynamics of free electron formation during the dissociation of interfacial charge transfer (CT) states. Motions of electrons and holes is scrutinized separately by selectively probing the Stark shift dynamics at selected wavelengths. It is shown that only charge pairs with an effective electron-hole separation distance of less than 4 nm are created during the dissociation of Frenkel excitons. Dissociation of the coulombically bound charge pairs is identified as the major rate-limiting step for charge carriers' generation. Interfacial CT states split into free charges on the time-scale of tens to hundreds of picoseconds, mainly by electron escape from the Coulomb potential over a barrier that is lowered by the electric field. The motion of holes in the small molecule donor material during the charge separation time is found to be insignificant.

中文翻译：

双层有机太阳能电池中电荷转移态的解离和载流子分离：时间分辨电吸收光谱研究

通过平面异质结花青染料/富勒烯有机太阳能电池中的斯塔克效应对电场进行超快光学探测，使人们能够直接监测界面电荷转移 (CT) 状态解离过程中自由电子形成的动力学。通过选择性地探测选定波长的斯塔克位移动力学，分别检查电子和空穴的运动。结果表明，在弗伦克尔激子的离解过程中，仅产生了有效电子-空穴分离距离小于 4 nm 的电荷对。库仑束缚电荷对的解离被认为是电荷载流子产生的主要限速步骤。界面 CT 状态在数十到数百皮秒的时间尺度上分裂成免费电荷，主要是通过电子从库仑势能越过被电场降低的势垒而逃逸。发现在电荷分离时间内小分子供体材料中空穴的运动是微不足道的。

更新日期：2015-06-19

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