The nature of trapping sites and recombination centres in PVK and PVKPBD electroluminescent matrices seen by spectrally resolved thermoluminescence

Ireneusz Glowacki (1) , Zbigniew Szamel (1)

1 CSEM - Centre Suisse d'Electronique et de Microtechnique SA [Neuchatel]

Two electroluminescent polymer matrices: poly(N-vinylcarbazole) (PVK) and PVK with 40 wt % of 2-tert-butylphenyl-5-biphenyl–1, 3, 4-oxadiazole (PBD) were studied using spectrally resolved thermoluminescence (SRTL) in temperature range 15-325 K. The comparison of the SRTL results with the electroluminescence (EL) spectra has allowed identifying the localized (trapping) sites and the radiative recombination centres present in the investigated matrices. In the neat PVK films deep traps with a depth about 200 meV, related to triplet excimers dominate, while in the PVK–PBD (40 wt %) blend films the traps that are related to triplet exciplexes formed by the carbazole groups and the PBD molecules dominate. Depth of the traps in the PVK–PBD blend is somewhat lower than that in the neat PVK. An analysis of the EL spectra shows that in the PVK and in the PVK–PBD blend the dominant radiative centres are singlet excimers and singlet exciplexes, respectively. However in the neat PVK some contributions of the triplet monomer and the triplet excimer states in the electroluminescence were also detected.

Mots clés: Physical Sciences

Ireneusz Glowacki, Zbigniew Szamel. The nature of trapping sites and recombination centres in PVK and PVKPBD electroluminescent matrices seen by spectrally resolved thermoluminescence. Journal of Physics D: Applied Physics, 2010, 43 (29), pp.295101. ⟨10.1088/0022-3727/43/29/295101⟩. ⟨hal-00569655⟩