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

Abstract

To cite this version:Ireneusz Glowacki, Zbigniew Szamel. The nature of trapping sites and recombination centres in PVK and PVKPBD electroluminescent matrices seen by spectrally resolved thermoluminescence. 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.

Electroluminescent Properties of an Electrochemically Cross‐Linkable Carbazole Peripheral Poly(Benzyl Ether) Dendrimer

“…Furthermore, this system should be practically suitable for comparing EL properties based on two different geometric structures (linear and dendritic structures). As shown in the EL spectra (Figure 2 b), two significant peaks are observed; the shorter wavelength originating from the PVK:PBD exciplex as reported before [8,19] and the longer wavelength due to the G 3 -cbz DN-related emission. The EL peaks (l e, EL ) of both devices (1 and 2) appear at near 434, 438 nm (shorter wavelength) and 482, 490 nm (longer wavelength), respectively.…”

Blue iridium complexes as electron trapping sites and efficient recombination centres in poly(N-vinylcarbazole) seen by spectrally resolved thermoluminescence

“…During heating of the sample, charge carriers are released from traps and, if they recombine radiatively, TL spectrum is registered. When spectral analysis of emitted light is simultaneously performed 3D plot of the SRTL results can be obtained (for example [17]). Nevertheless two-dimensional TL map (Fig.…”

“…Moreover, in the case of undoped PVK there are two broad bands: the dominant with maximum at 530 nm and second, weaker one with maximum at around 410 nm. The main band is associated with excimeric triplet states of carbazole groups, and short-wavelength broad band can be related to monomeric triplet excitons (about 430 nm) and to the singlet excimers of PVK (410 nm) [11,17].…”

“…The heating rate during SRTL runs was 7 K/min. The detailed SRTL procedure of experiment was described previously [17,18]. From the same solutions used for the fabrication of sample for SRTL experiments, thin layers (about 100 nm) were deposited by spin coating on quartz substrates for spectroscopic experiments.…”

“…Simultaneous registration of spectral distribution of the light emitted during the whole TL experiment allows identifying the origin of radiative recombination centres during detrapping processes. Therefore, the spectrally resolved thermoluminescence (SRTL) technique is applied for investigation of electroluminescent materials, especially emission layers based on host-quest systems [17,18].…”