Top-emitting thermally activated delayed fluorescence organic light-emitting devices with weak light-matter coupling

Abstract

Resonance interaction between a molecular transition and a confined electromagnetic field can lead to weak or strong light-matter coupling. Considering the substantial exciton–phonon coupling in thermally activated delayed fluorescence (TADF) materials, it is thus interesting to explore whether weak light-matter coupling can be used to redistribute optical density of states and to change the rate of radiative decay. Here, we demonstrate that the emission distribution of TADF emitters can be reshaped and narrowed in a top-emitting organic light-emitting device (OLED) with a weakly coupled microcavity. The Purcell effect of weak microcavity is found to be different for TADF emitters with different molecular orientations. We demonstrate that radiative rates of the TADF emitters with vertical orientation can be substantial increased in weakly coupled organic microcavity. These observations can enhance external quantum efficiencies, reduce efficiency roll-off, and improve color-purities of TADF OLEDs, especially for emitters without highly horizontal orientation.

Cavity-Suppressing Electrode Integrated with Multi-Quantum Well Emitter: A Universal Approach Toward High-Performance Blue TADF Top Emission OLED

“…3.2 , the Ag/WO 3 interfacial contact is ohmic, and the potential barrier between CSE/Al/LiF and DPPS (ETL) is equivalent to that between Ag/Al/LiF and DPPS because the bottom Ag in the CSE and the thin Ag electrode have the same work function. Therefore, the current density is essentially determined by the sheet resistance in both devices [ 46 ]. Additionally, the built-in potential produced across the WO 3 layer in the CSE helps establish a balanced electron flow, which increases the current density [ 21 ].…”

“…These broad EL spectra of Devices I and II (CSE-based devices) can be attributed to the suppressed microcavity effect in the CSE [ 54 ]. Although broad emission is beneficial for lighting applications, it indicates low color purity and is undesirable for display applications [ 46 ]. The lower FWHM value of Device I (≈ 60 nm) compared to that of Device II (≈85 nm) can be ascribed to the QW structure, which is consistent with previously reported OLEDs having the MQW structure [ 28 , 31 ].…”

“…3.1 . In previous studies, weak light-matter coupling was achieved using complex molecule structures or nanoporous polymer films, which involved complex processing techniques [ 13 , 16 , 46 ]. The design and use of a cavity-suppressed transparent cathode in blue TADF-TEOLEDs is described in this study, and it involves the use of facile fabrication techniques.…”

Air-Stable Ultrabright Inverted Organic Light-Emitting Devices with Metal Ion-Chelated Polymer Injection Layer

“…We calculated the power dissipation spectra (Fig. 3 f) of dipole sources at the EML/TCTA interface or the TPBi/EML interface with a homemade classic electromagnetic simulation software [ 32 ]. As shown in Fig.…”

Realization of Efficient Phosphorescent Organic Light-Emitting Devices Using Exciplex-Type Co-Host

“…Recently, exciplex-type co-hosts composed of acceptors and donors have been employed in highly efficient phosphorescent OLEDs, derived from their unique advantages of improved charge balance and exciton utilization [11]. Significantly, an exciplex system generally has a thermally activated delayed fluorescence (TADF) effect originating from the reverse intersystem crossing (RISC), due to the small singlet-triplet difference ( Est) [12]. Triplet excitons are capable of upconverting into singlet excitons as a result of the intrinsically small Est.…”