Molecular Packing and Morphology of Perylene Diimide Dianion-Based Thin Films: Insights from Molecular Dynamics Simulations

Perylene diimide dianion (PDI²⁻) is a promising organic semiconductor with exceptional electronic properties, but its application is limited by challenges in controlling the molecular packing and thin film morphology. In this work, we employed molecular dynamics (MD) simulations to investigate the structure and morphology of PDI²⁻ thin films during solvent evaporation. Our simulations captured the dynamic aggregation behaviors and interactions of PDI²⁻ molecules with solvent molecules during thin film formation. The effects of environmental factors, including residual solvent content, temperature, evaporation rate, and thermal annealing, on molecular packing and thin film morphology were considered. The results reveal that residual solvents play a critical role in promoting homogeneous molecular packing and preventing defect formation. Elevated temperatures enhance molecular ordering and thin film stability at an optimal evaporation temperature of 373.15 K, accompanied by an increase in hydrogen bond interactions. Thermal annealing further optimizes molecular packing and strengthens hydrogen bonding networks, thus yielding more stable and ordered thin films. GIWAXS-characterized images also support our simulation results. These findings provide a predictive guideline for optimizing the process parameters of PDI²⁻ thin film fabrication and offer molecular mechanism insights into the dynamic aggregation behaviors of PDI²⁻ molecules, also establishing a molecular structure foundation for investigating the electrical properties of high-performance organic semiconductors.