Study on Excited State Kinetics and Optical Limiting Performance of Triphenylamine-Based Chalcone Derivatives: Effect of the Molecular π-Conjugated Structure.

Abstract

Optical limiting (OL) is an important application of nonlinear optics. Summarizing the structure-property relationship of organic materials is an effective means to develop superior optical limiters. In this work, two triphenylamine-based chalcone derivatives T1 and T2 with different peripheral substituent groups were synthesized to study their transient kinetics and nonlinear optical (NLO) absorption performance. The transient absorption spectrum (TAS) of compounds T1 and T2 in solvents of varying polarities visualizes the intramolecular charge transfer (ICT) processes between the local excited state (LES) and the charge transfer state (CTS). Nanosecond Z-scan experiment and hole-electron analysis indicate that all compounds have excellent reverse saturated absorption (RSA) performance at 532 nm and T1 exhibits stronger RSA than T2 due to the stronger ICT performance of T1 caused by the halogen effect. Degenerate pump-probe experiment shows that the ESA of T2 at 532 nm is significantly enhanced by expanding the molecular π-conjugation. Under the premise of consistent linear transmittance (78%), compound T2 shows better OL performance than compound T1 at 532 nm in the nanosecond time domain. The OL thresholds of T1 and T2 are 3.72 and 0.72 J cm-2, respectively, which are better than those of the most reported OL materials. Our research shows that simple and common chalcone derivatives exhibit amazing NLO performance through a reasonable design.