Dual Hybridized Local and Charge Transfer Characteristic Fluorophore as an Efficient Nondoped Emitter for Electroluminescent Device

Hybridized local and charge transfer (HLCT) is an attractive strategy for achieving efficient electroluminescence (EL) in electrofluorescent devices by the conversion of triplet‐state (T) to singlet‐state (S) excitons via a reverse intersystem crossing, giving rise to a high exciton utilization efficiency exceeding the spin statistical limit. Excellent device performance is reached using thermally evaporated emissive layers. However, for potential large‐scale commercialization, it is crucial to attain comparable device performances using low‐cost solution‐processing techniques. Herein, a new concept of dual HLCT characteristic fluorophore (BCBF) with a high solid‐state fluorescence as a nondoped emitter for a simple structured solution‐processed EL device is presented. BCBF is effectively formulated by π‐conjugation linking two HLCT fragments with a highly soluble hole‐transporting aromatic moiety. Its dual HLCT and photoluminescence (PL) properties are experimentally and theoretically probed by the solvatochromic effect and density functional theory (DFT) calculations. The molecule exhibits an intense yellow–green emission with a good solution‐processed film‐forming quality and a high solid‐state fluorescence quantum yield of 80%. BCBF is successfully utilized as a nondoped emissive layer in a solution‐processed double‐layered organic light‐emitting diode (OLED), which shows excellent EL performance (brightness of 47 580 cd m−2, current efficiency of 15.78 cd A−1, and external quantum efficiency of 7.20%)

Additive-free molecular acceptor organic solar cells processed from a biorenewable solvent approaching 15% efficiency

We report on the use of molecular acceptors (MAs) and donor polymers processed with a biomass-derived solvent (2-methyltetrahydrofuran, 2-MeTHF) to facilitate bulk heterojunction (BHJ) organic photovoltaics (OPVs) with power conversion efficiency (PCE) approaching 15%. Our approach makes use of two newly designed donor polymers with an opened ring unit in their structures along with three molecular acceptors (MAs) where the backbone and sidechain were engineered to enhance the processability of BHJ OPVs using 2-MeTHF, as evaluated by an analysis of donor-acceptor (D-A) miscibility and interaction parameters. To understand the differences in the PCE values that ranged from 9-15% as a function of composition, the surface, bulk, and interfacial BHJ morphologies were characterized at different length scales using atomic force microscopy, grazing-incidence wide-angle X-ray scattering, resonant soft X-ray scattering, X-ray photoelectron spectroscopy, and 2D solid-state nuclear magnetic resonance spectroscopy. Our results indicate that the favorable D-A intermixing that occurs in the best performing BHJ film with an average domain size of ∼25 nm, high domain purity, uniform distribution and enhanced local packing interactions - facilitates charge generation and extraction while limiting the trap-assisted recombination process in the device, leading to high effective mobility and good performance.Air Force Office of Scientific Research12 month embargo; first published 05 October 2023This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]