Title : Fluorination-based molecular design of NDI and PDI copolymers for n-Type organic semiconductors
Abstract:
Efficient unipolar n-type semiconductors are crucial for the progress of organic electronic devices. In this work, we investigate how fluorination alters the properties of thiazole-flanked naphthalenediimide (NDI) and perylenediimide (PDI) copolymers incorporating benzothiadiazole (BT) units. Using a TIPS-assisted one-pot bromination method, we achieved streamlined synthesis of these electron-deficient building blocks, which were subsequently polymerized with both fluorinated and non-fluorinated BT acceptors. Comprehensive optical and electrochemical characterization showed that introducing fluorine consistently lowers LUMO energy levels, thereby enhancing electron injection and n-type performance. Fluorine incorporation was also found to affect molecular organization, as demonstrated by absorption spectra, cyclic voltammetry, and GIWAXS results. Moderate fluorination improved backbone planarity and π–π interactions, leading to higher electron mobility, whereas excessive fluorination disrupted packing and hindered charge transport. The optimized fluorinated copolymers delivered mobilities of up to 1.3 × 10⁻³ cm² V⁻¹ s⁻¹, underscoring fluorination as an effective strategy to tune electronic properties for advanced organic semiconductor applications.
