Thin-Film Morphology Control in Naphthalene-Diimide-Based Semiconductors: High Mobility n-Type Semiconductor for Organic Thin-Film Transistors

TLDR

In organic thin film transistors, film morphology and microstructure strongly influence charge carrier mobility and device performance. The study aims to design semiconducting molecules that yield predictable thin‑film morphology and optimal crystalline packing for high mobility. Introducing cyclohexyl end groups into naphthalene diimide directs intermolecular stacking, producing a crystalline packing that enhances field‑effect mobility. Vapor‑deposited N,N′‑bis(cyclohexyl) naphthalene‑1,4,5,8‑bis(dicarboximide) devices achieve field‑effect mobilities near 6 cm² V⁻¹ s⁻¹, among the highest reported for n‑ or p‑type organic semiconductors.

Abstract

In organic thin film transistors (OTFT), the morphology and microstructure of an organic thin film has a strong impact on the charge carrier mobility and device characteristics. To have well-defined and predictable thin film morphology, it is necessary to adapt the basic structure of semiconducting molecules in a way that results in an optimum crystalline packing motif. Here we introduce a new molecular design feature for organic semiconductors that provides the optimized crystalline packing and thin film morphology that is essential for efficient charge-carrier transport. Thus, cyclohexyl end groups in naphthalene diimide assist in directing intermolecular stacking leading to a dramatic improvement in field effect mobility. Accordingly, OTFT devices prepared with vapor deposited N,N′-bis(cyclohexyl) naphthalene-1,4,5,8-bis(dicarboximide) (1) regularly exhibit field effect mobility near 6 cm2/(V s), which is one of the highest carrier mobilities reported for either n- or p-type organic semiconducting thin films.