Solvent-conjugation-induced ultrafast dynamics of enhanced reverse saturable absorption in lead phthalocyanine derivatives solutions

With the continued development of high-power laser technology, research on laser protection has become extremely important. In this study, an analysis of Z-scan and femtosecond transient absorption spectra data for lead (II) tetrakis (4-cumylphenoxy) phthalocyanine (4-PbPc) solutions prepared using different concentrations and solvents established that charge transfer plays an important role in the optical limiting dynamics of this molecule. Based on the correlation of decay-associated difference spectra (DADS) for different decay channels, it was confirmed that greater charge transfer efficiency was associated with more highly conjugated solvent molecules. In a dilute solution, the polarity of the solvent molecules will influence the optical limiting performance of the solution to an extent, whereas in a highly concentrated solution, the degree of conjugation of the solvent molecules is the main influence. Therefore, the more highly conjugated the solvent and the higher the solution concentration, the higher the excited state absorption cross-section and effective two-photon absorption coefficient, and the longer the triplet lifetime. These results should provide theoretical guidance and experimental clues for the design of materials with better optical limiting performance and promote the further development of laser protection.