Ohmic Electron Injection into Organic Semiconductors by Solution‐Processed and Evaporated Organic Interlayers

Efficient electron injection from an electrode into an organic semiconductor remains a problem to solve for efficient organic semiconductor devices. In this work, a general method is presented to form an ohmic electron contact by inserting a thin organic interlayer between the metal electrode and the organic semiconductor. It is demonstrated that inserting an interlayer of a few nanometers of an organic semiconductor with a lower electron affinity than the transport material can improve the injected electron current by over three orders of magnitude. The electron current becomes space‐charge limited, demonstrating that the interlayer‐enhanced contact is ohmic. The ohmic‐contact formation by inserting a thin interlayer is ascribed to the elimination of barrier formation as a result of direct contact between the metal and organic semiconductor. Additionally, it is demonstrated that it is possible to achieve solution processing of such interlayers on top of organic semiconductors. The method is generalized for different interlayer materials as well as for different organic semiconductors, providing a general method for ohmic electron injection in organic devices. Efficient electron injection into organic semiconductors remains a problem to solve for efficient organic semiconductor devices. Here, a general method for efficient electron injection is provided, making use of a tunneling interlayer consisting of an organic semiconductor. The interlayer can be prepared from a variety of materials and can be deposited either by evaporation or from solution.