Image-Force-Stabilized Interfacial Dipole Layer Impedes Charge Injection Into Disordered Organic Semiconductors

作者：Liu, Feilong^*; Su, Yuhao; Lin, Xihong; Nian, Li; Wu, Bo; Niu, Quan; van Eersel, Harm; Bobbert, Peter A.; Coehoorn, Reinder^*; Zhou, Guofu^*

来源：Physical Review Applied, 2022, 17(2): 024003.

DOI：10.1103/PhysRevApplied.17.024003

• ENERGY-LEVEL ALIGNMENT
• METAL
• ELECTROLUMINESCENCE
• CONDUCTION
• TRANSPORT
• MOLECULES
• MOBILITY
• DEVICES

We show using three-dimensional kinetic Monte Carlo simulations that the injection of charge carriers from a metallic electrode into a disordered organic semiconductor is under nominally Ohmic injection conditions strongly impeded by the short-range Coulomb interactions between the charge carriers in the image-force-stabilized interfacial dipole layer. In contrast, master equation and conventional onedimensional drift-diffusion simulations underestimate these Coulomb interactions due to their mean-field approximation, and are found not to reveal the effect. The simulations predict a reduction of the current density in organic semiconductor devices when the nominal injection barrier is taken very small or even negative, consistent with recent experimental results [Kotadiya et al., Nat. Mater. 17, 329 (2018)]. However, whereas in that work a modification of the energetic disorder near the interface is assumed, we find that the effect is already obtained after including charge-charge interactions beyond a one-dimensional and mean-field approximation.