High-Efficiency Sky Blue-To-Green Fluorescent Emitters Based on 3-Pyridinecarbonitrile Derivatives

The pyridinecarbonitrile derivative is well known as an acceptor unit in fluorescent materials. However, its use in thermally activated delayed fluorescent (TADF) emitters is very limited compared with its benzenecarbonitrile counterparts. Very recently, we developed a series of 4-pyridinecarbonitrile, so-called isonicotinonitrile derivatives, as a highly efficient sky blue-to-green TADF emitters realizing low-drive-voltage organic light-emitting devices (OLEDs). In this work, we contributed new design and development for three 3-pyridinecarbonitrile-based TADF emitters named 2AcNN, 2PXZNN, and 5PXZNN. Among these emitters, a sky blue emitter, 2AcNN, showed a maximum external quantum efficiency (ηext,max) of 12% with CIE (0.19, 0.36). While green emitters, 5PXZNN and 2PXZNN, realized highly efficient TADF OLEDs with a ηext,max of 16–20%. Introduction of electron-donor moiety into the 2-position of 3-pyridinecarbonitrile contributes a larger overlapping of frontier molecular orbitals (FMOs) and stronger intramolecular charge transfer (ICT) interaction generating efficient TADF emitters

A minimal non- radiative recombination loss for efficient non- fullerene all- small- molecule organic solar cells with a low energy loss of 0.54 eV and high open- circuit voltage of 1.15 V+

Organic solar cells (OSCs) are considered as a promising next-generation photovoltaic technology because of their light weight, flexibility, and the potential of roll-to-roll fabrication. However, the relatively large energy loss (E-loss) from the optical bandgap (E-g) of the absorber to the open-circuit voltage (V-oc) of the device hinders further improvement of the PCEs of OSCs. Here, we report efficient non-fullerene all-small-molecule organic solar cells (NF all-SMOSCs), using DR3TBDTT and O-IDTBR as the donor and acceptor, respectively. We obtain a high electroluminescence yield (EQE(EL)) value of up to approximate to 4 x 10(-4) corresponding to a 0.21 eV non-radiative recombination loss, which is the smallest value for bulk-heterojunction (BHJ) OSCs so far. As a result, a low E-loss of 0.54 eV and a considerably high V-oc of 1.15 V are obtained for BHJ NF all-SMOSCs.Funding Agencies|Japan Science and Technology Agency (JST); Ministry of Education, Culture, Sports, Science and Technology (MEXT) through Center of Innovation (COI) Program; Swedish Energy Agency (Energimyndigheten) [2016-010174]</p

Low-Band-Gap Small Molecule for Efficient Organic Solar Cells with a Low Energy Loss below 0.6 eV and a High Open-Circuit Voltage of over 0.9 V

Small molecule organic solar cells (SMOSCs) have received considerable attention in recent years. However, one of the key factors limiting the performance of SMOSCs is their large energy loss (<i>E</i>_loss), which is typically between 0.6 and 1.0 eV, and therefore significantly higher than those of perovskite solar cells and inorganic solar cells (<i>E</i>_loss < 0.5 eV). Herein, we successfully report a new acceptor–donor–acceptor (A–D–A) type dimeric squaraine electron donor (<b>D-IDTT-SQ</b>) with a low optical band gap of 1.49 eV and deep HOMO energy level of −5.20 eV. Consequently, a high open-circuit voltage (<i>V</i>_oc) of 0.93 V with an impressive power conversion efficiency (PCE) of 7.05% is achieved for solution-processed bulk heterojunction SMOSCs, showing an <i>E</i>_loss of only 0.56 eV. This is the first report wherein SMOSCs result in such a low <i>E</i>_loss, while simultaneously exhibiting a considerably high <i>V</i>_oc over 0.9 V and an excellent PCE above 7.0%

A <i>m</i>-Terphenyl-Modifed Sulfone Derivative as a Host Material for High-Efficiency Blue and Green Phosphorescent OLEDs

A <i>m</i>-Terphenyl-Modifed Sulfone Derivative as a Host Material for High-Efficiency Blue and Green Phosphorescent OLED

High-performance pure blue phosphorescent OLED using a novel bis-heteroleptic iridium(III) complex with fluorinated bipyridyl ligands

A novel pure blue phosphorescent emitter FK306 with fluorinated bipyridyl ligands was developed. The I-p level was determined to be 6.3 eV by photoelectron yield spectroscopy (PYS) in the solid state. The photophysical properties of a FK306/mCP film were evaluated. An 11 wt% doped film showed a peak photoluminescence at 454 nm and a high photoluminescent quantum yield (eta(PL)) of 78 +/- 1%. A transient PL decay curve exhibited almost single-exponential decay (98%) with the phosphorescence lifetime (tau(p)) of 1.51 mu s at room temperature. A blue OLED with a structure of [ITO (130 nm)/TAPC (40 nm)/FK30611-20 wt% doped mCP (10 nm)/B3PyPB (50 nm)/LiF (0.5 nm)/Al (100 nm)] was fabricated and evaluated. A high power efficiency of over 30 lm W-1 and an external quantum efficiency of over 17% were observed. The CIE chromaticity diagram (x, y) was evaluated to be (0.16, 0.25), clearly indicating blue emission. These are the first decent performances using a blue emitter with bipyridyl ligands so far

Bis(Triphenylamine)Benzodifuran Chromophores: Synthesis, Electronic Properties and Application in Organic Light-Emitting Diodes

A series of bis(triphenylamine)benzodifuran chromophores have been synthesized and fully characterised. Starting from suitably functionalized benzodifuran (BDF) precursors, two triphenylamine (TPA) moieties are symmetrically coupled to a central BDF unit either at 4,8-positions through double bonds (1) and single bonds (2) respectively, or at 2,6-positions through double bonds (3). Their electronic absorption and photoluminescence properties as well as redox behaviour have been investigated in detail, indicating that the π-extended conjugation via vinyl linkers in 1 and 3 leads to comparatively strong electronic interactions between the relevant redox moieties TPA and BDF. Due to intriguing electronic properties and structural planarity, 3a has been applied as a dopant emitter in organic light-emitting diodes. A yellowish-green OLED exhibits a high external quantum efficiency (EQE) of 6.2%, thus exceeding the theoretical upper limit most likely due to energy transfer from an interface exciplex to an emissive layer and/or favorable horizontal orientation