A series of emitters displaying efficient photoluminescence (PL) and electroluminescence (EL) into the true- to sky-blue regions is herein described and employed as electroluminescent materials for the fabrication of efficient blue organic light-emitting diodes (OLEDs). The compounds possess linear, yet a twisted, donor-π-acceptor-π-donor (D-π-A-π-D) architecture, where D and A are a (substituted) carbazole (Cz) and thiazolo[5,4-d]thiazole (TzTz) moiety as the electron donor and accepting unit, respectively. D = 9H-carbazol-9-yl and 3,6-di-tert-butyl-9H-carbazol-9-yl for compounds TzTz-PCz2 and TzTz-PtbCz2, respectively. In dilute CH2Cl2solutions, both compounds display intense (PL quantum yield = 60-74%) and short-lived (τ = ca. 0.8-2.0 ns) luminescence arising from an intramolecular charge-transfer (1ICT) excited state and falling into the sky-blue to the greenish-blue region (λem= 448-502 nm). Compared to the previously reported TzTz-TPA parental emitters that features two triphenylamine (TPA) donor groups, the highly twisted nature and less extended π-conjugation of the donor-acceptor TzTz-PCz2 and TzTz-PtbCz2 counterparts herein presented enable to widen the HOMO-LUMO energy gaps and warrant blue shifting of the emission. Finally, OLED devices fabricated by employing the herein proposed emitters are presented as well with both single- and tandem-device architectures. The so-prepared OLEDs display true-blue to sky-blue EL peaking at λEL,max= 460 nm (TzTz-PCz2) and 467-470 nm (TzTz-PtbCz2) and achieve maximum external quantum efficiency and luminance of 10.2% and 44,851 cd m-2(for TzTz-PtbCz2) in the case of a tandem device, respectively, with a mitigated roll-off efficiency. These results demonstrate that the tandem device employing these TzTz donor-acceptor blue emitters raises the feasibility of fluorescent compounds to compete with other potential emitters in practical applications.
True- to Sky-Blue Emitters Bearing the Thiazolo[5,4- d]thiazole Electron Acceptor for Single and Tandem Organic Light-Emitting Diodes
Mauro M.
2023
Abstract
A series of emitters displaying efficient photoluminescence (PL) and electroluminescence (EL) into the true- to sky-blue regions is herein described and employed as electroluminescent materials for the fabrication of efficient blue organic light-emitting diodes (OLEDs). The compounds possess linear, yet a twisted, donor-π-acceptor-π-donor (D-π-A-π-D) architecture, where D and A are a (substituted) carbazole (Cz) and thiazolo[5,4-d]thiazole (TzTz) moiety as the electron donor and accepting unit, respectively. D = 9H-carbazol-9-yl and 3,6-di-tert-butyl-9H-carbazol-9-yl for compounds TzTz-PCz2 and TzTz-PtbCz2, respectively. In dilute CH2Cl2solutions, both compounds display intense (PL quantum yield = 60-74%) and short-lived (τ = ca. 0.8-2.0 ns) luminescence arising from an intramolecular charge-transfer (1ICT) excited state and falling into the sky-blue to the greenish-blue region (λem= 448-502 nm). Compared to the previously reported TzTz-TPA parental emitters that features two triphenylamine (TPA) donor groups, the highly twisted nature and less extended π-conjugation of the donor-acceptor TzTz-PCz2 and TzTz-PtbCz2 counterparts herein presented enable to widen the HOMO-LUMO energy gaps and warrant blue shifting of the emission. Finally, OLED devices fabricated by employing the herein proposed emitters are presented as well with both single- and tandem-device architectures. The so-prepared OLEDs display true-blue to sky-blue EL peaking at λEL,max= 460 nm (TzTz-PCz2) and 467-470 nm (TzTz-PtbCz2) and achieve maximum external quantum efficiency and luminance of 10.2% and 44,851 cd m-2(for TzTz-PtbCz2) in the case of a tandem device, respectively, with a mitigated roll-off efficiency. These results demonstrate that the tandem device employing these TzTz donor-acceptor blue emitters raises the feasibility of fluorescent compounds to compete with other potential emitters in practical applications.
Pubblicazioni consigliate
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
