Kinetics of Geminate Pair Recombination in Polyvinylcarbazole

Recombination of geminate electron hole pairs (GP) in Polyvinylcarbazole (PVK) has been investigated by (i) monitoring the decay of delayed luminescence (DF) following pulse excitation with 4.02 eV photons at temperatures between 20 K and 294 K and (ii) Monte Carlo computer simulation. It is found that the decay of the GP reservoir obeys a t−s law with s being close to unity and exhibiting small yet systematic variations depending on temperature and time domain. DF extends up to seconds even at 294 K delineating GP lifetimes accordingly long. It is concluded that recombination kinetics is controlled by both the intrinsic energetic disorder of the bulk hopping sites, i.e. the carbazole groups, and by intermediate trapping at presumably incipient carbazole dimers. The Noolandi, Hong and Street theory is found inadequate for data analysis because it ignores the energetic relaxation of carriers subject to random walk within the energy distribution of hopping sites generally present in amorphous solids.