Naphthalenediimide (NDI) derivatives have been widely employed as n-type semiconductors in electron transport layers (ETLs) for various solar cell architectures due to their favorable electron affinity and stability. Recently, the synthesis of axially substituted silane-functionalized naphthalenediimide (SNDI) incorporating triethoxysilane groups has been reported [1], enabling covalent anchoring and network formation via sol–gel chemistry. However, the influence of acid-catalyzed hydrolysis on the resulting thin-film structure and interfacial electronic properties remains poorly understood. This work aims to explain how the degree of acid-catalyzed hydrolysis influences the morphology, molecular ordering, optical vibronic structure, and electrochemical behavior of SNDI thin films. Thin films were fabricated by drop casting of hydrolyzed SNDI solutions with different hydrochloric acid concentrations of 1 mM, 10 mM and 100 mM onto plasma-treated ITO substrates at 40 °C on a hot plate, followed by thermal curing at 110 °C for 24 h. Surface wettability was analyzed using contact angle measurements, morphology by atomic force microscopy (AFM), optical properties by UV–vis spectroscopy, and electrochemical behavior by cyclic voltammetry. Decreasing acid concentration induces pronounced morphological changes, with AFM revealing a reduction in surface roughness from 79.30 nm (100 mM) to 30.98 nm (1 mM), indicating suppressed aggregation and improved film uniformity. Contact angle increases from 57.29° to 71.25°, reflecting increase in the hydrophobicity of the surface. Uv–vis spectra exhibit distinct vibronic transitions at 346, 365, and 388 nm, with the vibronic ratio A_(0-0)/A_(0-1)increasing from ~0.92 to ~1.10, indicating enhanced ?–? stacking coherence at lower hydrolysis levels. Cyclic voltammetry shows quasi-reversible redox behavior, with peak separation decreasing from 0.324 V to 0.288 V, consistent with improved electron transfer kinetics. The optical band gap remains constant at 3.2 eV, while the frontier orbital energies are essentially unchanged, with HOMO levels between ?6.917 eV (1 mM) and ?6.929 eV (100 mM), and LUMO levels of ?3.712 eV (1 mM) and ?3.719 eV (100 mM). These findings demonstrate that hydrolysis-controlled siloxane formation modulates supramolecular organization without altering intrinsic electronic structure. Reduced hydrolysis promotes smoother films, enhanced intermolecular coupling, and improved charge transfer, highlighting a viable strategy for optimizing SNDI-based ETLs in organic and hybrid solar cells.
Comissão Organizadora
Pedro Alves da Silva Autreto
Comissão Científica
Ferramenta completa de submissão, avaliação e publicação de anais para eventos científicos.
