Excited state absorption of 5CB (4′-n-pentyl-4-cyanobiphenyl) in cyclohexane Original Research Article

The excited state absorption (ESA) of 5CB (4′-n-pentyl-4-cyanobiphenyl) molecules dissolved in cyclohexane has been investigated for the singlet S1 and the triplet T1 state in the wavelength range from 380 to 870 nm. In this spectral range three different absorption bands have been resolved by time delayed measurements of the transient absorption and by changing the concentration of 5CB molecules. It is shown that the short living absorption may be attributed to a S1Sn transition band centered at 475 nm with a width of 42 nm (fwhm) plus an additional transient aggregate (exciplex) absorption, which was concentration dependent observed in the range from 380 to 450 nm. The long living component can be related to a triplet band centered at 402 nm with a halfwidth of 26 nm (fwhm). The triplet decay time was determined to 385 ns for the not degassed sample.