Figure 1
(a) Illustration of the layers that compose the standard PLED. (b, c) Illustration of the multilayered PLEDs containing solution-processed metal oxide layers. (d) Diagram showing the energy levels of all materials used in the PLEDs (values of work function, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were extracted from the literature).55 Duarte, L. G. T. A.; Germino, J. C.; Mendes, R. A.; Berbigier, J. F.; Moreira, K. S.; Faleiros, M. M.; de Freitas, J. N.; Burgo, T. A. L.; Rodembusch, F. S.; Atvars, T. D. Z.; J. Phys. Chem. C 2020, 124, 21036. [Crossref],2727 Skriver, H. L.; Rosengaard, N. M.; Phys. Rev. B 1992, 46, 7157. [Crossref]
28 Zheng, Q.; You, F.; Xu, J.; Xong, J.; Xue, X.; Cai, P.; Zhang, X.; Wang, H.; Wei, B.; Wang, L.; Org. Electron. 2017, 46, 7. [Crossref]
29 Li, X.; Xie, F.; Zhang, S.; Hou, J.; Choy, W. C. H.; Light: Sci. Appl. 2015, 4, e273. [Crossref]-3030 Alehdaghi, H.; Marandi, M.; Irajizad, A.; Taghavinia, N.; Jang, J.; Zare, H.; Mater. Chem. Phys. 2018, 204, 262. [Crossref] (e) Chemical structure of the polymers PVK and PFO.
Figure 2
(a) Current density, (b) luminance and (c) current efficiency as a function of the applied voltage; and (d) normalized EL spectra (at 8 V) for PLEDs with configuration: (▬) glass-ITO | PEDOT:PSS | PVK | PFO | Ca | Al (standard diode), (▬) glass-ITO | PEDOT:PSS | PVK | PFO | ZnO | Ca | Al and (▬) glass-ITO | PEDOT:PSS | PVK | PFO | ZnO-CD | Ca | Al.
Figure 3
(a) Current density, (b) luminance and (c) current efficiency as a function of the applied voltage, and (d) normalized EL spectra (at 10 V) for PLEDs consisting of glass-ITO | MoOx | PVK | PFO | ZnO | Ca | Al, where the MoOx films were processed at different temperatures: (▬) 150 ºC, (▬) 200 ºC, (▬) 250 ºC or (▬) 300 ºC.
Figure 5
(a) Current density, (b) luminance and (c) current efficiency as a function of the applied voltage; and (d) normalized EL spectra (at 10 V) for PLEDs consisting of glass-ITO | MoOx | PVK | PFO | Ca | Al, for different thicknesses of the MoOx layer: (▬) 33 nm, (▬) 41 nm, (▬) 55 nm, (▬) 72 nm or (▬) 80 nm.
Figure 6
(a) Current density, (b) luminance and (c) current efficiency as a function of the applied voltage; and (d) normalized EL spectra for PLEDs with configuration: (▬) glass-ITO | PEDOT:PSS | PVK | PFO | ZnO | Ca | Al, (▬) glass-ITO | MoO3 (evap.) | PVK | PFO | ZnO | Ca | Al and (▬) glass-ITO | MoOx (250 °C) | PVK | PFO | ZnO | Ca | Al.
Figure 8
(A) CIE chromaticity diagrams of PLEDs at 8 V of applied voltage: (a) glass-ITO | PEDOT:PSS | PVK | PFO | Ca | Al (standard diode), (b) glass ITO | PEDOT:PSS | PVK | PFO | ZnO | Ca | Al, (c) glass-ITO | PEDOT:PSS | PVK | PFO | ZnO-CD | Ca | Al and (d) glass-ITO | MoOx (250 °C) | PVK | PFO | ZnO | Ca | Al. Photography of the standard PLED (B) and the PLED containing the optimized MoOx film as HTL and ZnO as ETL (C).