Abstract:(2016) 'Exciplex enhancement as a tool to increase OLED device e ciency.', Journal of physical chemistry C., 120 (4). pp. 2070-2078. Further information on publisher's website:https://doi.org/10.1021/acs.jpcc.5b11263 Publisher's copyright statement: This document is the Accepted Manuscript version of a Published Work that appeared in nal form in Journal of physical chemistry C, copyright c American Chemical Society after peer review and technical editing by the publisher. To access the nal edited and pu… Show more
“…This needs to be studied in more detail though it can be sustained by the relative decrease of this second feature when the concentration of POZ-DBPHZ was increased from 8 to 11%.Figure 3Study of the concentration of POZ-DBPHZ in an orange-blue structure with relative concentrations of orange of 8% and 11%. ( a ) Electroluminescence (EL) spectra of both devices together with the EL of each material independently, taken from 36, 37 . ( b ) Electrical performance of the devices used for both structures.
…”
Section: Resultsmentioning
confidence: 99%
“…( a ) Electroluminescence (EL) spectra of both devices together with the EL of each material independently, taken from 36, 37 . ( b ) Electrical performance of the devices used for both structures.…”
We report on the engineering of full thermally activated delayed fluorescence – based white organic light emitting diodes (W-OLEDs) composed of three emitters (2,7-bis(9,9-dimethyl-acridin-10-yl)-9,9-dimethylthioxanthene-S,S-dioxide (DDMA-TXO2), 2,7-bis(phenoxazin-10-yl)-9,9-dimethylthioxanthene-S,S-dioxide (DPO-TXO2) and 3,11-di(10H-phenoxazin-10-yl)dibenzo[a,j]phenazine (POZ-DBPHZ) in two different hosts. By controlling the device design through the study of the emission of DDMA-TXO2 and DPO-TXO2, the behaviour of POZ-DBPHZ in a device with more than one emitter, and the combination of the three materials, respectively, we show that external quantum efficiencies as high as 16% can be obtained for a structure with a correlated colour temperature close to warm white, together with colour rendering index close to 80. However it is in their performance stability that provides the true breakthrough: at 1000 cd/m2 the efficiencies were still above 10%, which is one of the best for this type of devices.
“…This needs to be studied in more detail though it can be sustained by the relative decrease of this second feature when the concentration of POZ-DBPHZ was increased from 8 to 11%.Figure 3Study of the concentration of POZ-DBPHZ in an orange-blue structure with relative concentrations of orange of 8% and 11%. ( a ) Electroluminescence (EL) spectra of both devices together with the EL of each material independently, taken from 36, 37 . ( b ) Electrical performance of the devices used for both structures.
…”
Section: Resultsmentioning
confidence: 99%
“…( a ) Electroluminescence (EL) spectra of both devices together with the EL of each material independently, taken from 36, 37 . ( b ) Electrical performance of the devices used for both structures.…”
We report on the engineering of full thermally activated delayed fluorescence – based white organic light emitting diodes (W-OLEDs) composed of three emitters (2,7-bis(9,9-dimethyl-acridin-10-yl)-9,9-dimethylthioxanthene-S,S-dioxide (DDMA-TXO2), 2,7-bis(phenoxazin-10-yl)-9,9-dimethylthioxanthene-S,S-dioxide (DPO-TXO2) and 3,11-di(10H-phenoxazin-10-yl)dibenzo[a,j]phenazine (POZ-DBPHZ) in two different hosts. By controlling the device design through the study of the emission of DDMA-TXO2 and DPO-TXO2, the behaviour of POZ-DBPHZ in a device with more than one emitter, and the combination of the three materials, respectively, we show that external quantum efficiencies as high as 16% can be obtained for a structure with a correlated colour temperature close to warm white, together with colour rendering index close to 80. However it is in their performance stability that provides the true breakthrough: at 1000 cd/m2 the efficiencies were still above 10%, which is one of the best for this type of devices.
“…Aromatic amine based TPAF donor derived TPAF:B3PYMPM and Tris‐PCzB4PyPPM were also applied as exciplexes for DCJTB, but the EQE was below 10% . In addition, high‐EQE diketopyrrolopyrrole embedded fluorescent OLEDs were also developed using these exciplexes …”
Section: Singlet‐exciton‐harvesting Approaches For Fluorescent Oledsmentioning
OLEDs and TADF OLEDs are essential. One method to overcome those issues is to harvest singlet excitons by triplet-triplet fusion (TTF) process which converts triplet excitons into singlet excitons. [18][19][20] The TTF approach has been used in the blue fluorescent OLEDs, but the triplet to singlet conversion efficiency is limited, resulting in relatively low EQE compared to the phosphorescent and TADF OLEDs. The other method is to apply singlet-exciton-harvesting technology of fluorescent OLEDs by energy transfer to achieve high EQE and long device lifetime by overcoming the deficiencies of the two technologies. The EQE can be comparable to that of phosphorescent and TADF OLEDs if singlet excitons can be fully harvested, and the device lifetime can be better than that of those devices due to the intrinsic stability of the molecular structures and triplet excitons critical to the device lifetime are excluded in the final light-emission process.Herein, recent progress on the singlet harvesting approach of fluorescent emitters by an energy transfer process from host or sensitizer is discussed. Basic concepts, material requirements, and device architecture for the singlet-exciton-harvesting technology are covered to understand the light-emission process and to develop an ideal emitting layer system for both high EQE and long device lifetime. Additionally, future prospects of singletexciton-harvesting fluorescent OLEDs are proposed.
Basic Concept of Singlet-Exciton-Harvesting Fluorescent OLEDsFluorescent emitters can emit light by photoluminescence (PL) or electroluminescence (EL) processes although other processes such as chemiluminescence and mechanoluminescence can induce light emission. [21][22][23][24] In the PL process, fluorescent emitters can exhibit 100% photon conversion efficiency by light excitation if there is no intersystem crossing from the singlet excited state to triplet excited state and no loss during the radiative transition from singlet excited state to ground state. However, an ideal 100% PL efficiency is not realized in the EL process because 75% triplet excitons generated by the electrical carrier injection process are lost by nonradiative pathways. [25][26][27][28][29][30] Only 25% of the singlet excitons contribute to the EL emission process, and the internal quantum efficiency (IQE) of fluorescent OLEDs is limited to 25%. However, the low IQE of fluorescent OLEDs can be improved if triplet exciton The external quantum efficiency (EQE) of organic light-emitting diodes (OLEDs) has been dramatically improved by developing highly efficient organic emitters such as phosphorescent emitters and thermally activated delayed fluorescent (TADF) emitters. However, high-EQE OLED technologies suffer from relatively poor device lifetimes in spite of their high EQEs. In particular, the short lifetimes of blue phosphorescent and TADF OLEDs remain a big hurdle to overcome. Therefore, the high-EQE approach harvesting singlet excitons of fluorescent emitters by energy transfer processes from the host or sensit...
“…The electrochemical behavior of DPP derivatives in general is largely understood, it commonly comprises two oxidation processes and a single reduction process . The features seen in the new compounds are largely similar to those observed in N ‐alkyl DPPs (where a second irreversible reduction was seen at very negative potentials) . The oxidation processes are attributed to the comparatively electron rich flanking units and the single reduction arises from the electron accepting core.…”
Section: Resultsmentioning
confidence: 81%
“…[25] The features seen in the new compounds are largely similar to those observed in N-alkyl DPPs (where a second irreversible reduction was seen at very negative potentials). [39][40][41] The oxidation processes are attributed to the comparatively electron rich flanking units and the single reduction arises from the electron accepting core. The combined cyclic voltammograms for the 4MB type compounds ( Figure 2) show these traits, imparted by the 4MB group.…”
Section: Cyclic Voltammetry and Spectroelectrochemistrymentioning
A series of symmetrically bis‐4‐methoxybenzyl (4MB) N‐substituted 1,4‐diketopyrrolo[3,4‐c]pyrrole (DPP) derivatives have been synthesized. The 4MB unit makes the DPP core soluble, and shows subtle modification of up to 0.2 eV in ground and excited states of the core when compared with related alkyl derivatives. Absorption and emission spectroscopy, as well as electrochemical and computational methods have been employed to prove the importance of the peripheral aryl units on the donor/ acceptor properties of the molecules. The 4MB products are highly fluorescent (quantum yields approaching 100 % in solution), with a unique distribution of frontier states shown by spectroelectrochemistry. The solid‐state fluorescence correlates with the X‐ray crystal structures of the compounds, a Stokes shift of approximately 80 nm is seen for two of the compounds. The frontier energy levels show that this subtle substitutional change could be of future use in molecular energy level tailoring in these, and related, materials for organic (opto)electronics.
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