Competition between the formation of excimers and excitons during the photoluminescence of light-emitting polymer blends

Abstract

Divinylenediethylhexyloxyphenyl and either triphenyltriazine (PTPV) or diphenoxyphenyltriazine (POTPV) were alternately connected to inhibit the dimer emission of the divinylenediethylhexyloxyphenyl unit and to enhance the electron mobility of light-emitting polymers. A photoluminescence (PL) spectrum of a PTPV film showed characteristics of excimer emissions, whereas POTPV generated a singlet exciton PL emission. A blend of POTPV with poly(vinyl carbazole) (PVK) enhanced the PL intensity of POTPV upon the photoexcitation of PVK, and this indicated efficient energy transfer between the two polymers. Contrary to expectations based on the good overlap of spectra for the PL emission of the donor and the light absorption of the acceptor, the energy transfer from PVK to PTPV was incomplete upon the photoexcitation of the blend at the ultraviolet-visible absorption maximum of PVK. However, the excimer PL emission of PTPV was completely suppressed. The lifetime ratio of the excitations of the donor and the acceptor was proven to be one of the critical factors in the energy transfer, in addition to the Forster energy-transfer principle. The excimer emission was suppressed by the photoexcitation of the chromophores below a certain critical energy level. (C) 2003 Wiley Periodicals, Inc.