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Enhancing Reverse Intersystem Crossing via Secondary Acceptors: towards Sky-Blue Fluorescent Diodes with Tenfold-Improved Exter-nal Quantum Efficiency
摘要： How to simply but effectively facilitate reverse intersystem crossing (RISC) transition is always the key issue for developing high-performance thermally activated delayed fluorescence (TADF) dyes. In this work, as a proof of concept, a feasible strategy named 'acceptor enhancement' is demonstrated with a series of ternary blue emitters (xCzmPOnTPTZ) using diphenylphosphine oxide (PO) as secondary acceptors. Compared with its PO-free binary analogue, such simple introduction of PO groups in pCzPO2TPTZ dramatically enhances its RISC rate constant (kRISC) by 10 times to the level of ~105 s-1, accompanied by RISC efficiency (ηRISC) of 92%, which further improves the triplet-to-singlet upconversion for effective triplet harvesting in its devices. As the result, on the basis of a trilayer device structure, pCzPO2TPTZ realized a state-of-the-art external quantum efficiency (EQE) beyond 20% with tenfold improvement.
关键词： Organic Light-Emitting Diode,Thermally Activated Delayed Fluorescence,Excited State Transition,Blue Emission,Reverse Intersystem Crossing,Phosphine Oxide Acceptor
更新于2025-09-23 15:23:52
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Efficient Cathode Interfacial Materials Based on Triazine/Phosphine Oxide for Conventional and Inverted Organic Solar Cells
摘要： Cathode interfacial layers (CIL) have been applied in organic solar cells (OSCs) for the enhancement of photovoltaic characteristics. Most of them are employed in either conventional organic solar cells (COSCs) or inverted organic solar cells (IOSCs) only. Herein, we have designed and synthesized two cathode interfacial materials, namely, 3-(4,6-bis(4-bromophenoxy)-1,3,5-triazin-2-yl)-2,6-difluorophenyl)diphenylphosphine oxide (Br-PO-TAZ) and 4,4'-((6-(3-(diphenylphosphoryl)-2,4-difluorophenyl)-1,3,5-triazine-2,4-diyl)bis(oxy))dibenzonitrile (CN-PO-TAZ), and utilized them as CILs for both COSCs and IOSCs. The incorporation of our new CIL layers significantly enhanced the photovoltaic performance compared to COSCs and IOSCs without the CILs. The CN-PO-TAZ exhibited a power conversion efficiency (PCE) of 8.19% for COSCs and 8.33% for IOSCs, whereas Br-PO-TAZ yielded a PCE of 8.15% for COSCs and 8.23% for IOSCs, respectively. The improved performance was attributed to the multiple favorable factors: significantly reducing leakage current, decreasing series resistance, suppressing recombination, efficient charge transport and collection. Moreover, the CIL layers helped for sustaining device stability because they served as an internal shield against humidity.
关键词： cathode interfacial layers,organic solar cell,conventional/inverted,triazine/phosphine oxide unit,stability
更新于2025-09-19 17:13:59
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Starburst-type triarylphosphine oxide trimers forming a stable amorphous n-type layer in solution-processed multilayer OLED
摘要： Novel starburst-type triphenylphosphine oxide trimers PO-1 and PO-2 were synthesized aimed at application as an electron-transporting material for multilayer organic light-emitting diodes (OLEDs). They showed high glass transition temperatures (Tg; 175 and 205 (cid:1)C, respectively) and high lowest triplet energies (T1; 2.81 and 2.78 eV, respectively). Their high solubility in 2-propanol allowed us to fabricate multilayer OLEDs by solution processing, and a double-emitting layer OLED consisting of poly(9-vinylcarbazole)-based p-type and PO-1-based n-type layers doped with a phosphorescent material (FIrpic) showed efficient sky-blue electroluminescence with a maximum external quantum efficiency of 9.33%.
关键词： Solution processing,Organic light-emitting diode,Phosphine oxide,Double emitting layer,Multilayer,Electron-transporting material
更新于2025-09-16 10:30:52