Engineered solid-state aggregates in brickwork stacks of n-type organic semiconductors: a way to achieve high electron mobility

Abstract

Efficient, economically viable n-type organic semiconductor materials suitable for solution-processed OFET devices with high electron mobility and ambient stability are scarce. Merging these attributes into a single molecule remains a significant challenge and a careful molecular design is needed. To address this, synthetic viability (achievable in fewer than three steps) and using cost-effective starting materials are crucial. Our research presents a strategy that meets these criteria using naphthalene diimide (NDI) core structures. The approach involves a simple synthesis process with a cost of $ 5–10 per gram for the final products. This paper highlights our success in scaling up the production using affordable known reagents, creating ambient condition solution-processed OFET devices with impressive electron mobility, on–off current ratio (1 cm² V⁻¹ s⁻¹ and I_on/I_off ∼ 10⁹) and good ambient stability (more than 100 h). We conducted a comprehensive study on EHNDIBr₂, a material that demonstrates superior performance due to its unique supramolecular arrangement in its brickwork stack. This was compared with two similar structures to validate our findings. The superior performance of EHNDIBr₂ is attributed to the effective interlocking of charge-hopping units within the NDI core in its brickwork stack. Our findings include detailed electronic, spectroscopic, and microscopic analyses of these layers.