Highly Crystalline Selenium-Substituted C-Shaped Ortho-Benzodipyrrole-Based A-D-A-Type Nonfullerene Acceptor Enabling Solution-Processed Single-Crystal-Like Thin Films for Air-Stable, High-Mobility N-Type Transistors

C-shaped ortho-benzodipyrrole-based A-D_NB_ND-A non-fullerene acceptors (NFAs), derived from the removal of the A′ thiadiazole moiety in Y6, emerge as a new class of structurally simplified A-D-A-type NFAs. In this work, a selenium-substitution strategy is applied to the central D_NB_ND ladder-π-core, yielding asymmetric CB-Se and symmetric CB-2Se. Asymmetric CB-Se demonstrates a less ordered 3D trapezoid-like packing structure, which promotes a more favorable intermixed donor-acceptor morphology with PM6 polymer, achieving a higher power conversion efficiency (PCE) of 17.87% in organic photovoltaics (OPVs). This value represents the highest reported value among the selenium-incorporated A-D-A-type NFAs. Symmetric CB-2Se forms a kaleidoscope-like 3D single-crystal structure with enhanced intermolecular interactions. This enables the development of a single-crystal-like solution-processed thin film, which transitions from a kinetically trapped face-on π–π stacking orientation to a thermodynamically stable edge-on configuration upon thermal annealing. The CB-2Se-based organic field-effect transistor (OFET) achieved a remarkable electron mobility of 1.18 cm² V⁻¹ s⁻¹ with exceptional n-type air stability, which outperformed the corresponding A-D_NA′_ND-A-type Y6-based materials by two orders magnitudes and represents the highest reported value for solution-processed n-type OFETs utilizing A-D-A-type small molecules.