Tilted Spiro‐Type Thermally Activated Delayed Fluorescence Host for ≈100% Exciton Harvesting in Red Phosphorescent Electronics with Ultralow Doping Ratio

Abstract

Despite promising efficiency, the high fabrication cost due to the required high concentrations of noble metal based phosphors is still problematic for phosphorescent organic light‐emitting diodes (PhOLEDs). This situation becomes even serious considering some practical applications need high luminance, which in turn requires a higher concentration of emitters. A paradigm shift to circumvent these issues can be development of materials that are able to operate efficiently in very low concentrations (<1 wt%). Here, two thermally activated delayed fluorescence hosts (OSTFPCN and OSTFPB) with tilted spiro geometry, small singlet‐triplet splitting (Δ E st), and effective resonance energy transfer are developed. Within expectation, record performances with a power efficiency of 63.6 lm W−1 and an external quantum efficiency (EQE) of 31.2% for the red phosphor Ir(MDQ)2(acac) (2.0 wt%) are achieved with OSTFPCN as host. Additionally, a high power efficiency around 58 lm W−1 is also gained even at an ultralow dopant concentration of 0.5 wt% for a OSTFPB based device. Mechanism studies demonstrate that efficiency roll‐off can be effectively suppressed in such low concentrations. These findings pave a new way to exploit low cost and high efficiency PhOLEDs.

Flexible organic light-emitting diodes for antimicrobial photodynamic therapy

“…Bis(2-methyldibenzo [f,h]quinoxaline)(acetylacetonate) iridium(III) [Ir(MDQ) 2 (acac)] is a well-studied efficient red emitter, which has a photoluminescence (PL) peak at 610 nm in N,N′-Bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (NPB) host. [36][37][38] As shown in Fig. 1a, there is good overlap of the emission spectrum of Ir(MDQ) 2 (acac) and the absorption spectrum of MB, so effective photoexcitation of the photosensitizer is expected.…”

Synthesis and Charge‐Transporting Properties of Dibenzothiphene Dioxide‐Based Polysiloxanes

“…In addition, for both of PCzSi‐ alt ‐PDBTSi and PDBTSi, the HOMO‐1 and LUMO+1 are localized on completely different moieties. So the thorough‐paced separation of HOMO–LUMO implies that the migration of charge carriers in nonconjugated polymeric system is in consistent with “hopping mechanism” …”

Enhancing Molecular Aggregations by Intermolecular Hydrogen Bonds to Develop Phosphorescent Emitters for High‐Performance Near‐Infrared OLEDs

“…Since the seminal work of Tang and VanSlyke, organic light‐emitting devices (OLEDs) have attracted significant interest from both academia and commercial communities for their application in flexible displays and solid lightings . To date, the most efficient blue‐, green‐, orange‐, and red‐emitting OLEDs have all achieved external quantum efficiencies (EQEs) above 30% . Inspired by the successful development of visible light‐emitting OLEDs, the research on near‐infrared (NIR) OLEDs with an emission peak wavelength beyond 700 nm has drawn increasing attention because of their special applications in photodynamic therapy, night‐vision readable displays, and bio‐imaging .…”