Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA.
Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA.
Nature. 2018 Feb 1;554(7690):77-80. doi: 10.1038/nature25148. Epub 2018 Jan 18.
The unique properties of organic semiconductors, such as flexibility and lightness, are increasingly important for information displays, lighting and energy generation. But organics suffer from both static and dynamic disorder, and this can lead to variable-range carrier hopping, which results in notoriously poor electrical properties, with low electron and hole mobilities and correspondingly short charge-diffusion lengths of less than a micrometre. Here we demonstrate a photoactive (light-responsive) organic heterostructure comprising a thin fullerene channel sandwiched between an electron-blocking layer and a blended donor:C fullerene heterojunction that generates charges by dissociating excitons. Centimetre-scale diffusion of electrons is observed in the fullerene channel, and this can be fitted with a simple electron diffusion model. Our experiments enable the direct measurement of charge diffusivity in organic semiconductors, which is as high as 0.83 ± 0.07 square centimetres per second in a C channel at room temperature. The high diffusivity of the fullerene combined with the extraordinarily long charge-recombination time yields diffusion lengths of more than 3.5 centimetres, orders of magnitude larger than expected for an organic system.
有机半导体具有独特的性质，如柔韧性和轻便性，对于信息显示、照明和能源生产越来越重要。但是有机物受到静态和动态无序的影响，这可能导致载流子的可变范围跳跃，从而导致众所周知的较差的电性能，电子和空穴迁移率低，相应的电荷扩散长度小于一微米。在这里，我们展示了一种由薄富勒烯通道夹在电子阻挡层和掺杂物：C 富勒烯异质结之间的光活性（光响应）有机异质结构，通过离解激子产生电荷。在富勒烯通道中观察到厘米级的电子扩散，这可以用简单的电子扩散模型来拟合。我们的实验能够直接测量有机半导体中的电荷扩散率，在室温下 C 通道中的扩散率高达 0.83±0.07 平方厘米每秒。富勒烯的高扩散率与电荷复合时间的极长相结合，产生了超过 3.5 厘米的扩散长度，比有机体系预期的要大几个数量级。
