ON THE APPLICATION OF THERMOLUMINESCENCE FOR PROBING THE ENERGETIC DISORDER IN AMORPHOUS MOLECULAR-SOLIDS

The low-temperature thermoluminescence (TL) technique has been applied for probing the energetic disorder in doped poly(N-epoxypropylcarbazo le)(PEPC) polymer films, Strong polar dopants were used for varying th e degree of dipolar disorder, It was found that (1) the TL of the stud ied systems can be well interpreted in terms of the disorder model and (2) TL spectroscopy can provide the shape of the deepest part of the localised state distribution and the degree of energetic disorder as w ell. The charge trap distribution on the high-temperature side of the TL peak appears to be a Gaussian function and its halfwidth correlates well with the disorder parameter obtained from charge transport measu rements, An unusual electric field effect on the TL of PEPC doped with strong polar dopants was found and is explained in terms of the contr ibution of the charge-dipole interaction to the energy of localised st ates, This effect indicates that the TL phenomenon for the studied sys tems cannot be explained purely by molecular gamma-relaxation in the p olymer. (C) 1997 by John Wiley & Sons, Ltd.