Naturally Derived Organic Dyes for LED Lightings of High Color Rendering and Fidelity Index

Abstract

Light-emitting diodes (LEDs) are a lighting technology with a huge and ascending market. Typically, LED backlights are often paired with inorganic phosphors made from rare-earth elements (REEs) to tune the emission lineshapes for different applications. However, REE production is a resource-intensive process with many negative environmental impacts. Herein we develop organic hybrid LEDs using organic dyes synthesized from an abundant and non-toxic natural product (theobromine) to replace REE phosphors. The resulting hybrid LED generates continuous emission from 400 -740 nm, resulting in high color rendering index (the current industry standard) of 90 and color fidelity index (the most advanced and comprehensive standard) of 92, challenging commercial LEDs based on REE phosphors. In addition, the light-converting composite is made from 99 wt% SBS, an inexpensive industrial polymer, and 1wt% theobromine dyes, reducing the cost of the light converter to ¢1.30 for a 1 W LED, compared to approximately ¢ 19.2 of commercial products. The light converting efficiency of the dye-SBS composite is 82%. Excited state kinetics experiments were also conducted to provide guidance to further increase the light-converting efficiency of the theobromine dyes while maintaining excellent color rendering and fidelity. File list (2) download file view on ChemRxiv Supporting Information.pdf (610.92 KiB) download file view on ChemRxiv Theobromine and CRI CFI.pdf (1.00 MiB)

Humidity-Controlled Tunable Emission in a Dye-Incorporated Metal–Hydrogel–Metal Cavity

“…Manipulating the optical properties of an emitter is of paramount importance for developing efficient light sources for advanced nanophotonic devices, , fluorescence microscopy, and various optoelectronic applications . Over the past decades, numerous efforts have been made to control the emission properties of organic dye molecules, owing to their high photoluminescence (PL) quantum yield and broadband emission, paving the way for new solutions for photonic devices such as LEDs, lasers, and single-photon sources . To improve the efficiency and functionalities of the photonic devices, it is highly desirable to control and enhance the emission properties of the photonic structures.…”

Highly Efficient Quasi‐2D Green Perovskite Light‐Emitting Diodes with Bifunctional Amino Acid

“…Perovskite light-emitting diodes (PeLEDs) have been receiving mounting interest due to their tunable bandgap, solution processability, and high color purity. [1][2][3][4][5][6][7][8][9][10][11] A typical perovskite ABX 3 refers to [BX 6 ] 4− octahedron sheets layered between the A-site cations to form a three-dimensional structure. [12][13][14][15][16][17][18] However, such three-dimensional (3D) perovskites inherently possess small exciton binding energy (E b ) of tens of meV, [3,[19][20][21][22][23] resulting in a low electron-hole recombination rate and hence insufficient radiative recombination.…”

Systematic Investigation of Core and Endcap Selection on the Development of Functional π-Conjugated Materials

“…Moreover, the pyrrolic nitrogen not only provides a convenient synthetic handle for side-chain engineering but also enables for selective bromination of the NPDI framework (critical for efficient DHA) . Similarly to NPDI, theobromine has been identified by the Luscombe group as an environmentally friendly and sustainable electron-deficient endcap that is also amenable to DHA cross-coupling. − Not only do the functional groups of theobromine promote H-bonding but there is also an unfunctionalized nitrogen that can be alkylated to tune the solubility of the A–D–A-type materials. Beyond being DHA-compatible, using both NPDI and theobromine as endcaps could allow for the effects of endcap size and electron affinity on A–D–A-type molecule optoelectronic properties to be investigated.…”

“…A class of synthetically versatile organic compounds, known as π-conjugated materials, have been extensively used for a number of applications including charge transport/extraction, − light emission, − and even small-molecule catalysis. − Among the numerous π-conjugated material designs, the arrangement of electron-deficient (acceptor) and electron-rich (donor) organic units in an acceptor–donor–acceptor (A–D–A) motif has been popularized owing to the fact that the optical band gap, electron affinity, and/or redox stability can be easily tuned . Generally speaking, improved semiconducting properties are observed in A–D–A systems with an extended π-orbital overlap; this can be achieved by materials that exhibit either a highly planar ring-fused organic backbone or by those that promote conformational locking interactions between heteroatom-containing functional groups in the organic backbone. − ,, While nearly an infinite number of specialized organic building blocks may be pieced together to make these A–D–A π-conjugated materials, it is important that a reliable, selective, efficient, and atom-economical synthetic protocol be developed for these materials to ever be produced on the industrial scale. , With these criteria in mind, the use of direct (hetero)­arylation (DHA) to develop these π-conjugated materials has been leveraged as a highly effective cross-coupling method.…”

“…In these A–D–A systems, the optoelectronic properties can be readily modified by controlling the central electron-rich core (either by heteroatom tailoring or by extending π-conjugation). − ,− Thiophene is by far one of the most prevalent building blocks in π-conjugated materials, where 3,4-ethylenedioxythiophene (EDOT) is particularly well-suited for highly efficient and selective DHA cross-coupling because it does not have any β-H available for C–H activation. ,, Seeking to exploit this favorable feature of EDOT, while also probing the influence of the central core π-extension on the overall optoelectronic properties for a related A–D–A′–D–A system, an EDOT-flanked benzothiadiazole core was also viewed as a suitable aryl core. , It was theorized that the heteroatoms of EDOT and benzothiadiazole would engage in conformational locking interactions to promote planarity and thus extend π-conjugation. By using both sets of identified electron-deficient endcaps and electron-rich cores, we designed, synthesized, and characterized four new π-conjugated systems.…”