Abstract Naphthalene tetracarboxylic diimides (NDIs) are highly promising air‐stable n ‐type molecular semiconductor candidates for flexible and cost‐effective organic solar cells and thermoelectrics. Nonetheless, thermal and polymorphic stabilities of environmentally stable NDIs in the low‐to‐medium temperature regime (<300 °C) remain challenging properties. Structural, thermal, spectroscopic, and computational features of polyfluorinated NDI‐based molecular solids (with up to 14 F atoms per NDI molecule) are discussed upon increasing the fluorination level. Slip‐stacked arrangement of the NDI cores with suitable π–π stacking and systematically short interplanar distances (<3.2 Å) are found. All these materials exhibit superior thermal stability (up to 260 °C or above) and thermal expansion coefficients indicating a response compatible with flexible polymeric substrates. Optical bandgaps increase from 2.78 to 2.93 eV with fluorination, while LUMO energy levels decrease down to −4.37 eV, as shown per DFT calculations. The compounds exhibit excellent solubility of 30 mg mL −1 in 1,4‐dioxane and DMF.