Efficient Deep-Blue Fluorescent OLEDs with High Exciton Utilization Efficiency from a Fully Twisted Phenanthroimidazole-Anthracene Emitter
Abstract
A novel, efficient, deep-blue fluorescent emitter mPAC, with meta-connected donor-acceptor structure, containing phenanthroimidazole (PPI) as the donor, and phenylcarbazole substituted anthracene (An-CzP) as the acceptor, was designed and synthesized. The meta-linkage provided highly twisted molecular conformation, which efficiently interrupts the intramolecular π-conjugation, results in deep-blue emission. The optimized non-doped device based on mPAC displayed deep-blue emission with a narrow full width at half maximum (FWHM) of 56 nm and Commission Internationale de L'Eclairage (CIE) coordinates of (0.16, 0.09). The maximum external quantum efficiency (EQEmax) is 6.76%, corresponding a high exciton utilization efficiency (EUE) of 59.3-88.9%. Experimental results and theoretical analysis indicated that the high EUE is mainly ascribed to the reverse intersystem crossing (RISC) from T2 to S1, a "hot exciton" path, in which, the large T2-T1 energy gap (1.45 eV) and small T2-S1 energy difference (0.18 eV, T2＞S1) hampers the internal crossing (IC) from T2 to T1 and facilitates the RISC process. For the "hot exciton" path, the T2 state can be feasibly arranged to a high energy level, forming a thermal equilibrium with S1, even slightly higher than the deep-blue S1 to realize an exergonic RISC process, which is usually difficult for the thermally activated delayed fluorescence (TADF) emitters.
Read the paper
Related studies
- Chaos and quantum thermalization
- The Dalton quantum chemistry program system
- Cord Blood Leptin and Adiponectin as Predictors of Adiposity in Children at 3 Years of Age: A Prospective Cohort Study
- Quantitative metabolomics by H-NMR and LC-MS/MS confirms altered metabolic pathways in diabetes
- Stable adiabatic quantum batteries
- A novel self-lipid antigen targets human T cells against CD1c(+) leukemias
Go deeper in Evidence Hub
Evidence Hub adds a study data sheet (design, sample size, evidence level, key numbers), an AI summary and a chat grounded in the paper's text.