Enhanced Electroluminescence Efficiency Using Reverse Intersystem Crossing Induced by the Strong Triplet Fusion of Rubrene as a Sensitizer

Abstract

Current-dependent MEL and MC experimental curves of Dev. 1 at room temperature and 100 K and at 100 μA; temperature-dependent MEL curves of device 3 at 100 μA; rubrene and DCJTB concentration-dependent MEL experimental curves of Dev. 1; and schematic diagram of spin-pair states in Dev. 1 with a high DCJTB doping concentration (PDF)■ AUTHOR INFORMATION

Hyperfluorescence-Based Emission in Purely Organic Materials: Suppression of Energy-Loss Mechanisms via Alignment of Triplet Excited States

“…In particular, Dexter energy transfer between the triplet states of the TADF and fluorescent molecules must be largely precluded in order to avoid the generation of nonradiative triplet excitons (T 1 FE ) on the fluorescent emitters. − The important question that then arises is whether Dexter energy transfer could be minimized by a rational choice of the fluorescent emitter. Here, in order to address this question, we have investigated the electronic structure of a series of fluorescent emitters (see Figure ) that were recently used in hyperfluorescence-based OLED devices: 2,5,8,11-tetra- tert -butylperylene (TBPe), ,,,, 9,10-bis­[ N , N -di­( p -tolyl)-amino]­anthracene (TTPA), ,− 2,8-di- tert -butyl-5,11-bis­(4- tert -butylphenyl)-6,12-diphenyltetracene (TBRb), ,,,,− 5,6,11,12-tetraphenyltetracene (rubrene), − and tetraphenyldibenzoperiflanthene (DBP), ,, and terrylene …”

Disorder‐Induced Dispersive Magneto‐Electroluminescence of Blue Emitters in Organic Light Emitting Diodes

“…Xin Pan, Ohyun Kwon,* Dipak Raj Khanal, Byoungki Choi, and Zeev Valy Vardeny* DOI: 10.1002/adom.202101334 rates can be tuned by an external magnetic field B, which modulates the EL emission intensity giving rise to magneto-EL (MEL) of which response is an efficient tool for investigating the e-h pair dynamics in the active layer of the device. [2][3][4][5][6][7][8][9][10][11][12][13][14] The MEL(B) response requires spinmixing activity among the four spin sublevels of the spin-entangled e-h pairs, namely intersystem-crossing between singlet and triplet spin configurations; which is dominated by various spinrelated interactions. [2][3][4][5][6]10,11,[16][17][18] These include the hyperfine interaction (HFI), spin orbit coupling (SOC), and also the difference, Δg of the Landé g-factors of the electron and hole constituents of the e-h species, known as the "Δg mechanism".…”

“…[2][3][4][5][6][7][8][9][10][11][12][13][14] The MEL(B) response requires spinmixing activity among the four spin sublevels of the spin-entangled e-h pairs, namely intersystem-crossing between singlet and triplet spin configurations; which is dominated by various spinrelated interactions. [2][3][4][5][6]10,11,[16][17][18] These include the hyperfine interaction (HFI), spin orbit coupling (SOC), and also the difference, Δg of the Landé g-factors of the electron and hole constituents of the e-h species, known as the "Δg mechanism". [19] In the following discussion we will focus on the "Δg mechanism".…”

“…The magnetic field effect has been proven to be a powerful tool for investigating the spin-dependent processes associated with spin-pair species in organic-based devices, especially in organic light emitting diodes (OLEDs). [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Upon carriers' injection into the organic active layer of the device, the principal process that counts is the formation of spin-entangled electron and hole (e-h) pairs which generate singlet and triplet excitons; or, alternatively dissociate into free carries. These OLED processes may be studied indirectly by measuring the device electro-luminescence (EL) versus bias voltage V (namely EL-V) and current density, J versus V (J-V response).…”

“…These OLED processes may be studied indirectly by measuring the device electro-luminescence (EL) versus bias voltage V (namely EL-V) and current density, J versus V (J-V response). [2][3][4][5][6][7][8][9][10] Importantly, it has been shown that the e-h recombination and dissociation has a Lorentzian line shape only if the spin-pair lifetime, τ is a single value. [21] In molecular OLEDs, the amorphous nature of the organic active layer, especially when vacuum-deposited may lead to a broad distribution of spin relaxation times, [22,23,24] and therefore the Lorentzian MEL(B) response may not occur frequently.…”