Enhanced Triplet Formation in Polycrystalline Tetracene Films by Femtosecond Optical-Pulse Shaping

Abstract

Polycrystalline tetracene films have been explored using weak ∼ 30 fs visible laser pulses that excite the lowest singlet exciton as well as coherent vibrational motion. Transient difference spectra show a triplet absorption which arises following singlet fission (SF) and persists for 1.6 ns without decay. Adaptive pulse shaping identifies multipulse optimal fields which maximize this absorption feature by ∼ 20%. These are comprised of subpulses separated by time delays well correlated with the period of lattice vibrations suggesting such modes control the yield of SF photochemistry.

Polarization-dependent exciton dynamics in tetracene single crystals

“…Roughly speaking, the late-stage signal (~ 3 ns, Fig. 2 Moreover, it is noticeable that the signal at 2.45 eV shows the feature of triplet exciton dynamics as reported in literatures, 14,22,40 which is likely to be associated to the feature of T → observed in tetracene solution. 14,40 We can now get a better understanding of the SF process in tetracene concerning the polarization dependences of different processes.…”

“…4 In parallel to the impressive development in device engineering, efforts have been made to unravel the physical mechanisms behind such interesting phenomena. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Most of the experimental and theoretical works have focused on the material family of polyacenes.…”

“…9,10,12,14,17,18,22,29,30,[38][39][40][41][42][43][44][45] In crystalline tetracene, SF is very efficient although it is a slightly endothermic process. In the latest studies on tetracene with transient optical spectroscopy, the fission rate has been characterized 9,12,14,17,23 and an intermediate multiexciton state has been identified to mediate the SF process.…”

“…12,22 Two possible reasons may cause such slight divergences. First, the polarization effect has been clearly extracted in this work which was not considered in the earlier studies of tetracene films.…”

Communication: Probing non-equilibrium vibrational relaxation pathways of highly excited C≡N stretching modes following ultrafast back-electron transfer

“…This in turn opens up the possibility of optimizing the efficacy of charge transfer in molecular materials by manipulating the vibrational density of states within the ground and excited electronic states by chemical synthesis or coherent control with light. 5,6 Detailing vibrational energy flow in polyatomic molecules during ultrafast photoinduced chemical reactions in solution requires experimental tools that can measure coupled electronic and vibrational degrees of freedom with femtosecond time resolution.…”