High Current Injection into Dynamic p–n Homojunction in Polymer Light‐Emitting Electrochemical Cells

Sakanoue, Tomo; Li, Jinpeng; Tanaka, Hisaaki; Ito, Ryota; Ono, Shimpei; Kuroda, Shin–ichi; Takenobu, Taishi

doi:10.1002/adma.201606392

Cited by 38 publications

(46 citation statements)

References 37 publications

(47 reference statements)

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“…This preliminary test was performed by mixing the metallopolymers with the ionic liquid BMIM-PF 6 . Homogeneous thin films of the blends were obtained by spin-coating technique [21,24,63,64,65,66,67,68]. Interestingly, the addition of 10% wt.…”

Section: Resultsmentioning

confidence: 99%

A Highly Efficient White Luminescent Zinc (II) Based Metallopolymer by RGB Approach

2019

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Three aryl-hydrazone O,N,O tridentate ligands with a different electron-withdrawing substituent were prepared. The introduction of a flexible charged chain in the ligands guaranteed solubility in many organic solvents and in water. The increasing withdrawing aptitude of the substituents red-shifted the emission in the correspondent metallopolymers. The metallated polymers were obtained by grafting ligand-zinc (II) coordination fragments onto commercial poly-(4-vinylpyridine). Metallopolymers thin films exhibited red, green and blue emission colors defined by Commission Internationale d’Eclairage (CIE) coordinates and medium to excellent photoluminescence (PL) quantum yields (PLQYs) comparable with other highly-performing active materials for Light-Emitting Diodes (LEDs). By grafting a suitable mix of the three different coordination pendants, an efficient single-component white emissive metallopolymer with CIE (0.30, 0.31) was prepared. Thanks to the charged moiety, the polymers resulted miscible with an ionic liquid. The addition produced homogeneous polymeric layers with unaltered PL performances, potentially employable in Light-emitting Electrochemical Cells (LECs).

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Section: Resultsmentioning

confidence: 99%

A Highly Efficient White Luminescent Zinc (II) Based Metallopolymer by RGB Approach

2019

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“…However, BSBCz still has room for improvement. First, BSBCz is practically insoluble while solution processability is highly desired and would facilitate not only low‐cost fabrication but also the fabrication of nanostructures, the dispersion of dyes into polymer matrices, and the mixing of dyes with electrolyte to produce light‐emitting electrochemical cells . Second, the electron affinity of BSBCz is relatively low because the molecular structure lacks electron‐withdrawing groups or electron‐accepting units, resulting in a low electron mobility and a wide energy gap of ≈3 eV.…”

Section: Introductionmentioning

confidence: 99%

Low Amplified Spontaneous Emission Threshold from Organic Dyes Based on Bis‐stilbene

Mamada

Fukunaga

Bencheikh

et al. 2018

Adv Funct Materials

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Advanced organic laser dyes exhibiting high solubility and bipolar behavior are developed based on a structure combining bis-stilbene with carbazole (BSBCz). The materials show high photoluminescence quantum yields and large radiative rate constants in solutions, crystals, and blend and neat films. The introduction of alkyl groups significantly improves the solubility of BSBCz, and solution-processed films of the alkyl-substituted derivatives exhibit amplified spontaneous emission thresholds as low as 0.59 µJ cm −2 , which is comparable to those of vacuum-deposited BSBCz films. On the other hand, cyano-substitution on BSBCz (BSBCz-CN) increases electron-accepting properties, resulting in a bathochromic shift of the emission wavelength and improved bipolar behavior. In a BSBCz-CN-doped film, a low ASE threshold of 0.63 µJ cm −2 is achieved, which is one of the lowest values for organic laser dyes with green emission. In addition, organic light-emitting diodes based on BSBCz-CN neat films exhibit external quantum efficiencies of 1.8% and could withstand injection of high current densities of up to 500 A cm −2 under pulse operation. These properties along with low excited-state absorption cross sections make these materials an outstanding addition to the existing library of organic laser dyes, especially for consideration in electrically pumped lasers.

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“…In particular, the rapid increase in current at 1.2 V can be attributed to the threshold voltage for doping. 14,23) Further importantly, light emission was clearly observed by the IL application: the emission started to be observed at around 3.4 V. This indicates the realization of the simultaneous injections of electrons and holes. Importantly, the turn-on voltage of 3.4 V is almost the same as the bandgap energy E gap of GaN.…”

Section: Characterization Of Gan Single Crystalmentioning

confidence: 80%

GaN light-emitting device based on ionic liquid electrolyte

Hirai¹,

Sakanoue²,

Takenobu³

2018

Jpn. J. Appl. Phys.

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Ionic liquids (ILs) are attractive materials for fabricating unique hybrid devices based on electronics and electrochemistry; thus, IL-gated transistors and organic light-emitting devices of light-emitting electrochemical cells (LECs) are investigated for future low-voltage and high-performance devices. In LECs, voltage application induces the formation of electrochemically doped p-n homojunctions owing to ion rearrangements in composites of semiconductors and electrolytes, and achieves electron-hole recombination for light emission at the homojunctions. In this work, we applied this concept of IL-induced electrochemical doping to the fabrication of GaN-based light-emitting devices. We found that voltage application to the layered IL/GaN structure accumulated electrons on the GaN surface owing to ion rearrangements and improved the conductivity of GaN. The ion rearrangement also enabled holes to be injected by the strong electric field of electric double layers on hole injection contacts. This simultaneous injection of holes and electrons into GaN mediated by ions achieves light emission at a low voltage of around 3.4 V. The light emission from the simple IL/GaN structure indicates the usefulness of an electrochemical technique in generating light emission with great ease of fabrication.

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High Current Injection into Dynamic p–n Homojunction in Polymer Light‐Emitting Electrochemical Cells

Cited by 38 publications

References 37 publications

A Highly Efficient White Luminescent Zinc (II) Based Metallopolymer by RGB Approach

A Highly Efficient White Luminescent Zinc (II) Based Metallopolymer by RGB Approach

Low Amplified Spontaneous Emission Threshold from Organic Dyes Based on Bis‐stilbene

GaN light-emitting device based on ionic liquid electrolyte

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