Light Emission Properties of a Cross-Conjugated Fluorene Polymer: Demonstration of Its Use in Electro-Luminescence and Lasing Devices

Abstract

Light emission properties of a fluorene cross-conjugated polymer (PF-1) based on the monomer 4,7-bis[2-(9,9-dimethyl)fluorenyl] benzo[1,2,5]thiadiazole are reported. This polymer exhibits solubility at high concentrations, good processability into thin solid films of good quality and a broad emission band with a fluorescence quantum yield of approximately 1. Based on these features, in this paper we implemented the use of PF-1 as an active layer in polymer light-emitting diodes (PLEDs) and as a laser gain medium in solution. To get insight on the conducting properties of PF-1, two different electron injectors, poly [(9,9-bis(3 1 -(N,N-dimethylamino) propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) and lithium fluoride (LiF), were used in a simple PLED architecture. PLEDs with the PFN film were found to exhibit better performance with a maximum luminous efficiency of 40 cd/A, a turn-on voltage (V on ) of approximately 4.5 V and a luminance maximum of 878 cd/m 2 at 5.5 V, with a current density of 20 A/m 2 . For the lasing properties of PF-1, we found a lasing threshold of around 75 µJ and a tunability of 20 nm. These values are comparable with those of rhodamine 6G, a well-known laser dye.

Enhanced Optoelectronic Properties of PFO/Fluorol 7GA Hybrid Light Emitting Diodes via Additions of TiO2 Nanoparticles

“…Despite recent advancement, conjugated polymers, which are well known as active materials in various photovoltaic [ 1 , 2 ] and electroluminescence [ 3 , 4 , 5 ] devices, continue to inherit two major problems, namely poor stability and low luminance efficiency [ 6 , 7 ]. The main reason for the former lies on photo-oxidation, while the latter is closely associated with low charge carrier mobility and high-energy barrier for its injection.…”

Efficient OLEDs Fabricated by Solution Process Based on Carbazole and Thienopyrrolediones Derivatives

“…Signal was previously quantified by a highly sensitive lux meter and correlated with the photodiode voltage response. All data acquisition routines were automated by using LabVIEW software specially designed for this purpose [ 55 ]. External quantum efficiency (EQE) was determined from the J-V, L-V plots and the electroluminescence (EL) spectrum, through the elementary approach reported by Shukla M. et al [ 56 ] and S. Chen [ 57 ].…”

Tyrian purple: an ancient natural dye for cross-conjugated n-type charge transport

“…6 Recently, Zhang et al reported high hole mobilities in diketopyrrolopyrrole (DPP) based cross-conjugated polymers. 7 Other common building blocks have been exploited in cross-conjugated polymers including isoindigo, 8,9 fluorene, [10][11][12][13] carbazole, 14 and some more atypical systems, [15][16][17][18][19][20] however successful application in devices is rarely reported.…”