Effect of a twin-emitter design strategy on a previously reported thermally activated delayed fluorescence organic light-emitting diode

Authors thank EU Horizon 2020 Grant Agreement No. 812872 (TADFlife) for funding this project. Further support was obtained by the Helmholtz Association Program at the Karlsruhe Institute of Technology (KIT). The German Research Foundation (formally Deutsche Forschungsgemeinschaft DFG) in the framework of SFB1176 Cooperative Research Centre "Molecular Structuring of Soft Matter" (CRC1176, A4, B3, C2, C6) and the cluster 3D Matter Made To Order all funded under Germany’s Excellence Strategy 2082/1--390761711 are greatly acknowledged for financial contributions. We acknowledge support from the Engineering and Physical Sciences Research Council of the UK (grant EP/P010482/1), from the International Collaborative Research Program of Institute for Chemical Research, Kyoto University (grant # 2020-37 and 2021-37), and from JSPS KAKENHI Grant Number JP20H05840 (Grant-in-Aid for Transformative Research Areas, “Dynamic Exciton”). ZZ acknowledges the financial support from the China Scholarship Council (CSC, 201606890009) for his PhD studies. EZ-C is a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089).In this work we showcase the emitter DICzTRZ in which we employed a twin-emitter design of our previously reported material, ICzTRZ . This new system presented a redshifted emission at 488 nm compared to that of ICzTRZ at 475 nm and showed a comparable photoluminescence quantum yield of 57.1% in a 20 wt% CzSi film versus 63.3% for ICzTRZ . The emitter was then incorporated within a solution-processed organic light-emitting diode that showed a maximum external quantum efficiency of 8.4%, with Commission Internationale de l’Éclairage coordinate of (0.22, 0.47), at 1 mA cm−2.Publisher PDFPeer reviewe

What controls the orientation of TADF emitters?

Thermally-activated delayed fluorescence (TADF) emitters—just like phosphorescent ones—can in principle allow for 100% internal quantum efficiency of organic light-emitting diodes (OLEDs), because the initially formed electron-hole pairs in the non-emissive triplet state can be efficiently converted into emissive singlets by reverse intersystem crossing. However, as compared to phosphorescent emitter complexes with their bulky—often close to spherical—molecular structures, TADF emitters offer the advantage to align them such that their optical transition dipole moments (TDMs) lie preferentially in the film plane. In this report, we address the question which factors control the orientation of TADF emitters. Specifically, we discuss how guest-host interactions may be used to influence this parameter and propose an interplay of different factors being responsible. We infer that emitter orientation is mainly governed by the molecular shape of the TADF molecule itself and by the physical properties of the host—foremost, its glass transition temperature Tg and its tendency for alignment being expressed, e.g., as birefringence or the formation of a giant surface potential of the host. Electrostatic dipole-dipole interactions between host and emitter are not found to play an important role

Corrigendum:What Controls the Orientation of TADF Emitters? (Front. Chem., (2020), 8, (750), 10.3389/fchem.2020.00750)

In the original article, there was a mistake in Supplementary Figure S8 of the Supplementary Material, and derived from that, in Table 1 as well as Figures 7A, 8A as published. The measured values of the GSP for two of the host materials, viz. BCPO and PO9, were interchanged by mistake. These values also resulted in a wrong calculation of the degree of PDMalignment (Λ). The corrected Table 1 as well as Figures 7A, 8A are attached below. (Figure presented.). The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article and the Supporting Material have been updated.</p

Twin-emitter design strategy for use in solution-processable thermally activated delayed fluorescence organic light-emitting diodes

In this work we showcase the emitter DICzTRZ in which we employed a twin-emitter design of our previously reported material, ICzTRZ. This new system presented a red-shifted emission at 488 nm compared to that of ICzTRZ at 475 nm and showed a comparable photoluminescence quantum yield of 57.1% in a 20 wt% CzSi film versus 63.3% for ICzTRZ. The emitter was then incorporated within a solution-processed organic light-emitting diode that showed a maximum external quantum efficiency of 8%, with Commision Internationale de l’Éclairage coordinate of (0.21, 0.47), at 10 cd m−2

Efficient sky-blue organic light-emitting diodes using a highly horizontally oriented thermally activated delayed fluorescence emitter

Funding: Deutsche Forschungsgemeinschaft (Grant Number(s): SFB1176), Engineering and Physical Sciences Research Council (Grant Number(s): EP/P010482/1), China Scholarship Council (Grant Number(s): 201606890009), H2020 Marie Skłodowska-Curie Actions (Grant Number(s): 812872).Organic thermally activated delayed fluorescent (TADF) materials can harvest 100% of the electrically generated excitons as a result of their small singlet-triplet energy difference. However, maximizing the External Quantum Efficiency (EQE) of a device also requires enhancing the light-outcoupling efficiency. In this work, we present a new Acceptor-Donor-Acceptor (ADA) emitter employing an indolocarbazole donor and diphenyltriazine acceptors that shows nearly-completely horizontal orientation regardless of the host matrix, leading to a sky-blue OLED (λEL=483nm, CIE coordinates of 0.17, 0.32) with EQEMAX of 22.1%, a maximum luminance of 7800 cd/m2 and blue emission.Publisher PDFPeer reviewe