The First Tandem, All-exciplex-based WOLED

Abstract

Exploiting our recently developed bilayer interface methodology, together with a new wide energy-gap, low LUMO acceptor (A) and the designated donor (D) layers, we succeeded in fabricating an exciplex-based organic light-emitting diode (OLED) systematically tuned from blue to red. Further optimization rendered a record-high blue exciplex OLED with ηext of 8%. We then constructed a device structure configured by two parallel blend layers of mCP/PO-T2T and DTAF/PO-T2T, generating blue and yellow exciplex emission, respectively. The resulting device demonstrates for the first time a tandem, all-exciplex-based white-light OLED (WOLED) with excellent efficiencies ηext: 11.6%, ηc: 27.7 cd A−1, and ηp: 15.8 ml W−1 with CIE(0.29, 0.35) and CRI 70.6 that are nearly independent of EL intensity. The tandem architecture and blend-layer D/A (1:1) configuration are two key elements that fully utilize the exciplex delay fluorescence, providing a paragon for the use of low-cost, abundant organic compounds en route to commercial WOLEDs.

Highly efficient tandem full exciplex orange and warm white OLEDs based on thermally activated delayed fluorescence mechanism

“…Different from Hung et al paper that showed a cool white emission [28], we earned a warm white OLEDs and the correlated color temperature (CCT) was 3723 K. Because warm white give a sweet, soft and warm feel, so our WOLEDs is more suitable for home lighting compared with the WOLEDs in Ref. [28]. The characteristic emission peaks of two exciplex with the blue sub-band around 451 nm and orange sub-band around 570 nm are observed in the white EL spectra, respectively.…”

“…7(d) shows the EL spectra of the WOLEDs under various voltages. Different from Hung et al paper that showed a cool white emission [28], we earned a warm white OLEDs and the correlated color temperature (CCT) was 3723 K. Because warm white give a sweet, soft and warm feel, so our WOLEDs is more suitable for home lighting compared with the WOLEDs in Ref. [28].…”

“…The achievement of such a high EQE is ascribed to the contribution of TADF and efficient CGL. Recently, Hung et al reported a tandem, all-exciplex WOLEDs [28]. Their WOLEDs realized the maximum efficiencies at a very low luminance and suffered from a very high operation voltage.…”

Thermally Activated Delayed Fluorescence in Polymer–Small-Molecule Exciplex Blends for Solution-Processed Organic Light-Emitting Diodes

“…Moreover, a vast majority of recently studied efficient TADF intermolecular exciplexes show that the CT states are located well below the triplets of the donor and acceptor moieties. 22,25,39 Therefore, we conclude that, for intermolecular exciplex systems, the most common energy layout is the one where the 3 LE state lies above the 1 CT, and where the involvement of the local triplet state in the RISC is unlikely. Previous studies suggested that the ISC and RISC processes due to spin−orbit coupling between pure singlet and triplet charge transfer states is forbidden.…”

“…Because of the prominent filmforming properties of poly(N-vinylcarbazole), 31,32 the blend can potentially be used in inkjet or slot-die printing. 2,4,6-Tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine (PO-T2T), 25 which is used as an acceptor, shows excellent solubility in toluene, which helps in the formation of highquality films.…”