Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Eindhoven, The Netherlands.
Phys Rev Lett. 2012 Feb 10;108(6):066601. doi: 10.1103/PhysRevLett.108.066601. Epub 2012 Feb 8.
While it is known that the charge-carrier mobility in organic semiconductors is only weakly dependent on the electric field at low fields, the experimental mobility in organic field-effect transistors using silylethynyl-substituted pentacene is found to be surprisingly field dependent at low source-drain fields. Corroborated by scanning Kelvin probe measurements, we explain this observation by the severe difference between local conductivities within grains and at grain boundaries. Redistribution of accumulated charges creates very strong local lateral fields in the latter regions. We further confirm this picture by verifying that the charge mobility in channels having no grain boundaries, made from the same organic semiconductor, is not significantly field dependent. We show that our model allows us to quantitatively model the source-drain field dependence of the mobility in polycrystalline organic transistors.
虽然已知有机半导体中的电荷载流子迁移率在低场下仅弱依赖于电场,但使用硅基乙炔基取代的并五苯的有机场效应晶体管中的实验迁移率在低源漏场下却出人意料地表现出对电场的依赖性。通过扫描开尔文探针测量得到证实,我们通过晶粒内部和晶界之间的局部电导率的巨大差异解释了这一观察结果。累积电荷的再分配在后者区域中产生非常强的局域横向电场。我们通过验证由相同有机半导体制成的没有晶界的通道中的电荷迁移率对电场没有明显依赖性进一步证实了这一结果。我们表明,我们的模型允许我们对多晶有机晶体管中的迁移率的源漏场依赖性进行定量建模。