Reduction of aggregation in NIR-absorbing films with heptamethine cyanine dyes through steric hindrance and polymer interaction

Near-infrared (NIR) absorbing films are essential components of CMOS image sensors. To address aggregation issues in benzo[cd]indolenyl-substituted heptamethine cyanines, we synthesized four derivatives with meso-position substituents designed to increase steric hindrance and enhance polymer interactions. These modifications effectively reduced aggregation and improved film performance. Cyanine dyes with stronger steric hindrance (e.g., Cy-5eB) mitigated aggregation in polystyrene (PS) films, while those with stronger polymer interactions (e.g., Cy-5caB) performed better in cyclic olefin polymer (COP) films. Furthermore, Cy-5caB exhibited enhanced thermal stability in COP films, indicating that increasing polymer interactions not only reduces aggregation but also improves thermal stability.