Determination of trap states in ladder type polymers

Electrically active defects have a profound impact on the semiconducting pr operties of conjugated polymer systems. Defect-induced thermally stimulated current (TSC), technique is used to probe the trap levels in these polymer s. Detailed TSC investigations in oriented and as cast films of poly(benzim adazobenzophenanthroline) BBL, a ladder-type, high-temperature conjugated p olymer are carried out. We estimate the energetics and the density of the t rap states in BBL using this technique. Results obtained from complimentary experiments such as long-lived photocurrent studies are correlated with th at obtained from TSC. We also demonstrate the applicability of this approac h to characterise trap states in other conjugated polymer systems such as p oly-3-octylthiophene, P3OT and poly(2-methoxy-5-(2'-ethylhexoxy)-1,4-para-p henylenevinylene) (MEHPPV). (C) 2001 Elsevier Science B.V. All rights reser ved.