Rational design of visible light panchromatic absorption laser dye molecules: The first principle study

Laser dye molecules play an important role in tunable lasers due to enhancing the laser radiation intensity and increasing the laser adjustable range. The broad spectral bandwidth and visible light absorption allows for the evaluation of multiple fluorescence quenching mechanisms such as excition formation, photoinduced electron transfer, and excited-state proton transfer. A series of organic dye molecules (LD1-4、LA2-5、LU1-5、LV1-4、LI1-4) consisting of simple electron donor (D), conjugated bridge (π) and electron acceptor (A) units were designed using first-principles calculations in order to evaluate their potential for applications in tunable lasers. Furthermore, the optical and electronic properties of the dye molecules are analyzed in detail using density functional theory (DFT) and time-dependent density functional theory (TDDFT), including spectral parameters, energy levels and orbital contributions of organic dye molecules. The results indicate that LI1-3 show high molar extinction coefficient, visible light full color absorption and obvious red-shifted compared to the experimentally synthesized dye LA3. In particular, the newly designed LI3 exhibits not only a 190 nm red-shifted and a higher molar extinction coefficient with an increment of 19%, but also has an extremely broad absorption spectrum covering entire visible absorption spectrum from 380 to 750 nm compared to LD1. We also find that the dyes with dithiophene groups and naphthalene group as the electron donors are better absorption spectrum than dyes with double bond group and benzene group. These calculated results will hopefully contribute to the further development of novel laser dye molecules and further provide scientific support and theoretical guidance for subsequent related research.