Naphthalene Diimide‐Based Small‐Molecule Semiconductors Enabling Air‐Stable n‐Type Organic Field‐Effect Transistors

The development of ambient‐stable n‐type organic semiconductors is a critical yet challenging research frontier. Herein, we report a rational molecular design by functionalizing naphthalene diimide (NDI) cores with strong electron‐withdrawing termini via thiophene bridges. Density functional theory calculations revealed enhanced planarity and significantly lowered lowest unoccupied molecular orbitals energy level (<−4.1 eV), which were corroborated by photophysical and electrochemical analyses. The solution‐processed organic field‐effect transistors (OFETs) demonstrated electron mobilities over 10 −3 cm 2 V −1 s −1 , all of which were fabricated and measured under ambient conditions. Remarkably, the devices retained >97% performance after 2‐week storage in ambient conditions. Furthermore, to evaluate the potential of the semiconductors for flexible electronics applications, we fabricated flexible OFETs by integrating the self‐assembled NDI‐4X (X = F, Cl) thin films prepared via air‐water interfacial self‐assembly. Also under ambient conditions, the devices exhibited higher electron mobilities of 4.49 × 10 −3 (NDI‐4F) and 7.21 × 10 −3 cm 2 V −1 s −1 (NDI‐4Cl) than their halogen‐free counterpart NDI‐4H (1.14 × 10 −3 cm 2 V −1 s −1 ). This work demonstrates that introducing strong electron‐withdrawing groups at both ends of electron‐deficient units provides an effective pathway to achieve ambient‐stable n‐type small‐molecule semiconductors, thereby enabling their application in next‐generation, ambient‐operating flexible organic electronics.