Introduction.
The development of multifunctional organic materials capable of combining optical modulation with reversible charge storage is highly relevant for emerging sustainable energy technologies. Electrochromic materials that modulate light transmission while simultaneously storing electrical energy are promising for energy-efficient systems such as smart windows and hybrid electrochromic–energy storage devices. Naphthalene diimide (NDI) derivatives are well-known electron-acceptor units due to their low-lying LUMO levels, high electrochemical stability, and efficient electron-transport properties. When combined with electron-donor groups such as carbazole, donor–acceptor architectures can provide ambipolar electrochemical behavior and tunable optical responses. Here, we investigate the electrochemical generation and functional properties of thin films derived from an NDI-based molecule bearing two carbazole units (NDI-2CBZ).

Methods.
The electrochemical behavior of NDI-2CBZ was studied by cyclic voltammetry on glassy carbon and ITO electrodes. Anodic oxidation of the carbazole groups induces electropolymerization, forming surface-confined electroactive films. The resulting materials were characterized by electrochemical and spectroelectrochemical techniques to evaluate their redox processes, optical switching properties, and charge storage performance.

Results.
NDI-2CBZ shows well-defined redox processes associated with reduction of the NDI core and oxidation of carbazole units. Repetitive anodic cycling leads to stable electroactive films. The electrodeposited material exhibits reversible doping–dedoping processes accompanied by potential-dependent optical changes, revealing electrochromic switching behavior. Galvanostatic charge–discharge measurements display quasi-triangular profiles characteristic of pseudocapacitive behavior. The films exhibit areal capacitances of 0.52 mF cm⁻² (n-doped) and 0.13 mF cm⁻² (p-doped) at 0.01 mA cm⁻². Cycling tests show capacitance retentions of ~60% after 1000 cycles for n-doped films and ~70% after 3000 cycles for p-doped films.

Conclusions.
Electropolymerized NDI–carbazole films combine ambipolar redox activity, reversible electrochromic switching, and pseudocapacitive charge storage. Their optical modulation capability, reversible ion-coupled charge storage, and good cycling stability highlight their potential for electrochromic devices and hybrid energy storage systems for improved energy efficiency.