Luminescent organic materials based on donor-acceptor-donor compounds containing carbazole donors and acceptors of varying strength: Spectroscopy, redox properties and application in organic light emitting diodes

• Published in: Optical materials Vol. 108; p. 110428
• Main Authors: Rybakiewicz, Renata, Ganczarczyk, Roman, Wiosna-Salyga, Gabriela, Bobowska, Izabela, Banasiewicz, Marzena, Charyton, Martyna, Skorka, Lukasz, Zagorska, Malgorzata, Pron, Adam
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2020
• Subjects: Carbazole donors; Donor-acceptor-donor compounds; Organic light emitting diodes; Redox properties; Spectroscopy; Organic light emitting diodes; Spectroscopy; Donor-acceptor-donor compounds; Redox properties; Carbazole donors
• ISSN: 0925-3467; 1873-1252; 1873-1252
• DOI: 10.1016/j.optmat.2020.110428

Three D-π-Α-π-D organic luminophores of tunable donor-acceptor interactions were synthesized by combining carbazole D-units with two different A units, namely 2,5-dithiophen-2-yl-[1,3,4]-thiadiazole and benzo[c][1,2,5]thiadiazole. In the third compound tert-butyl groups were introduced to the carbazole ring to increase its electron-donating properties. This compound, namely 4,7-bis(4-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)benzo[c][1,2,5]thiadiazole (CBTD2) turned out to be a very good photoluminophore showing the photoluminescence quantum yield (φ) of 62% in toluene solution and 45% when dispersed in a solid blend consisting of poly(vinylcarbazole) (PVK) and 2-([1,1′-biphenyl]-4-yl)-5-(4'-(tert-butyl)-[1,1′-phenyl]-4-yl)-1,3,4-oxadiazole (PBD). Moreover, its electrochemically determined ionization potential (IP = 5.55 eV) and electron affinity (EA = −2.73 eV) made it a very promising candidate for application as an active component in light emitting diodes of guest/host configuration with PVK-PBD matrix. The fabricated diodes of the following structure ITO/PEDOT:PSS/PVK-PBD + CBTD2/Ca/Ag showed the luminance reaching 6000 cd/m2 with luminous efficiency of 1 cd/A. •Donor-acceptor-donor compounds of low and tunable band gap.•Effect of donor-acceptor interaction on spectroscopic and electrochemical properties.•High solution and solid state photoluminescence quantum yield.•Luminance up to 6000 cd/m2 and luminous efficiency of 1 cd/A for guest/host type LED.