Enhanced Luminescence Efficiency Research Articles

Polymorph controlled synthesis and photoluminescence properties of Eu3+ doped BiNbO4

Homogeneous doping of rare earth (RE) ions at atomic level is ideal for enhancing luminescence efficiency. Molten-salt synthesis facilitates crystal growth with improved phase-selectivity and dopant homogeneity. Herein, we present a facile and phase-selective synthesis of orthorhombic α-BiNbO4 and monoclinic β-BiNbO4 under Na2SO4-K2SO4 fluxes in the temperature range of 900 °C to 1050 °C. A series of Eu3+ doped BiNbO4 samples with different crystalline structures were obtained. The influences of Eu3+ doping on the crystal structure were systematicly investigated. α-BiNbO4 has a higher Eu3+-doping limit (>15 mol%) while β-BiNbO4 was unstable upon Eu3+ doping and gradually transformed into α-BiNbO4 with the increase of Eu3+ doping concentration. Moreover, all prepared Eu3+ doped BiNbO4 samples can be effectively excited by near-ultraviolet and blue light and exhibit intense red emissions due to the 5D0/7F2 transition of Eu3+ ions. In addition, the quenching concentration can reach above 10 mol% Eu3+ for both polymorphs. The temperature-dependent emission results revealed that α-BiNbO4 possesses a superior thermal stability with activation energy of 0.271 eV, larger than β-BiNbO4 with activation energy of 0.233 eV. The results reported here provide new insights into the understanding of polymorph-dependent property for photon down-conversion rare-earth luminescence of BiNbO4:Eu3+.

Enhancing the Light Extraction Efficiency in Micro‐Organic Light‐Emitting Diodes with Metalens

Enhancing Luminescence Efficiency In article number 2000145, Haowen Liang and coworkers demonstrate that, by introducing the metalens, the trapped energy/light in micro-OLEDs can be converted into direct emission, leading the outcoupling efficiency of micro-OLEDs to be boosted to a high level, which is of potential for ultrahighpixel- density micro-displays required in emerging augmented reality (AR)/virtual reality (VR).

PEG-Neridronate-Modified NaYF4:Gd3+,Yb3+,Tm3+/NaGdF4 Core-Shell Upconverting Nanoparticles for Bimodal Magnetic Resonance/Optical Luminescence Imaging.

Upconverting nanoparticles are attracting extensive interest as a multimodal imaging tool. In this work, we report on the synthesis and characterization of gadolinium-enriched upconverting nanoparticles for bimodal magnetic resonance and optical luminescence imaging. NaYF4:Gd3+,Yb3+,Tm3+ core upconverting nanoparticles were obtained by a thermal coprecipitation of lanthanide oleate precursors in the presence of oleic acid as a stabilizer. With the aim of improving the upconversion emission and increasing the amount of Gd3+ ions on the nanoparticle surface, a 2.5 nm NaGdF4 shell was grown by the epitaxial layer-by-layer strategy, resulting in the 26 nm core–shell nanoparticles. Both core and core–shell nanoparticles were coated with poly(ethylene glycol) (PEG)-neridronate (PEG-Ner) to have stable and well-dispersed upconverting nanoparticles in a biological medium. FTIR spectroscopy and thermogravimetric analysis indicated the presence of ∼20 wt % of PEG-Ner on the nanoparticle surface. The addition of inert NaGdF4 shell resulted in a total 26-fold enhancement of the emission under 980 nm excitation and also affected the T1 and T2 relaxation times. Both r1 and r2 relaxivities of PEG-Ner-modified nanoparticles were much higher compared to those of non-PEGylated particles, thus manifesting their potential as a diagnostic tool for magnetic resonance imaging. Together with the enhanced luminescence efficiency, upconverting nanoparticles might represent an efficient probe for bimodal in vitro and in vivo imaging of cells in regenerative medicine, drug delivery, and/or photodynamic therapy.

Improving the Overall Properties of Circularly Polarized Luminescent Materials Through Arene–Perfluoroarene Interactions

AbstractA major trade‐off in the field of circularly polarized luminescence (CPL) of pure organic materials is that the large luminescence dissymmetry factor (glum) usually gives rise to the suppression of luminescence efficiency (ΦPL). Here, a supramolecular self‐assembled system, driven by arene–perfluoroarene (AP) interactions of chiral polycyclic aromatic hydrocarbons (PAHs) and octafluoronaphthalene (OFN), is reported to provide a solution to this problem. Two kinds of chiral PAHs based on pyrene and anthracene could co‐assemble with OFN in hybrid solvents to form long‐range‐ordered AP assemblies. The detailed process of AP interaction driving self‐assembly was verified by morphological measurements and fluorescence spectra. The AP assemblies exhibited chirality amplification not only in the excited state but also in the ground state. In addition, the AP assemblies showed an enhanced luminescence efficiency compared with the individual chiral PAHs due to the energy‐barrier effect of OFN. The present strategy based on AP interactions could be applied to boost the development of highly efficient CPL‐active materials.

Improving the Overall Properties of Circularly Polarized Luminescent Materials Through Arene-Perfluoroarene Interactions.

A major trade-off in the field of circularly polarized luminescence (CPL) of pure organic materials is that the large luminescence dissymmetry factor (glum ) usually gives rise to the suppression of luminescence efficiency (ΦPL ). Here, a supramolecular self-assembled system, driven by arene-perfluoroarene (AP) interactions of chiral polycyclic aromatic hydrocarbons (PAHs) and octafluoronaphthalene (OFN), is reported to provide a solution to this problem. Two kinds of chiral PAHs based on pyrene and anthracene could co-assemble with OFN in hybrid solvents to form long-range-ordered AP assemblies. The detailed process of AP interaction driving self-assembly was verified by morphological measurements and fluorescence spectra. The AP assemblies exhibited chirality amplification not only in the excited state but also in the ground state. In addition, the AP assemblies showed an enhanced luminescence efficiency compared with the individual chiral PAHs due to the energy-barrier effect of OFN. The present strategy based on AP interactions could be applied to boost the development of highly efficient CPL-active materials.

A facile approach for the creation of heteroionic lanthanidomesogens-containing uniform films with enhanced luminescence efficiency

Adducts of Eu(III), Tb(III), Gd(III) and La(III) tris(β-diketonate) forming mesophases in close temperature ranges were synthesized. The near structural features of these lanthanidomesogens render them suitable for obtaining homogeneous binary mixtures that vitrified on cooling into optically isotropic, self-organizing smectic films over a wide range ratio of the lanthanide complexes. The distribution of the components in the obtained films and their supramolecular organization were studied by polarizing optical microscopy, differential scanning calorimetry, and small-angle X-ray scattering. The mixtures behave as their homologous single components and exhibit smectic A and nematic phases above room temperature, and form anisotropic glasses at room temperature. The dependence of the luminescence on the ratio of each component in the mixtures under investigation has been established and a photoexcitation mechanism proposed. It was shown that the luminescence intensity per mole of the emitting substance in films obtained from mixtures of Eu(III) and Tb(III) complexes increases about three fold when compared with the individual Eu(III) complex. This enhancement of the luminescence was interpreted as the consequence of the very effective intermolecular energy transfer from Tb(III) to Eu(III) complexes, templated by the frozen smectic A supramolecular organization. We thus present here an efficient and facile approach for the creation of novel heteroionic lanthanide-containing high uniaxial materials with effective luminescence and controlled spectral properties.

Efficient and stable blue quantum dot light-emitting diode.

The visualization of accurate colour information using quantum dots has been explored for decades, and commercial products employing environmentally friendly materials are currently available as backlights1. However, next-generation electroluminescent displays based on quantum dots require the development of an efficient and stable cadmium-free blue-light-emitting device, which has remained a challenge because of the inferior photophysical properties of blue-light-emitting materials2,3. Here we present the synthesis of ZnSe-based blue-light-emitting quantum dots with a quantum yield of unity. We found that hydrofluoric acid and zinc chloride additives are effective at enhancing luminescence efficiency by eliminating stacking faults in the ZnSe crystalline structure. In addition, chloride passivation through liquid or solid ligand exchange leads to slow radiative recombination, high thermal stability and efficient charge-transport properties. We constructed double quantum dot emitting layers with gradient chloride content in a light-emitting diode to facilitate hole transport, and the resulting device showed an efficiency at the theoretical limit, high brightness and long operational lifetime. We anticipate that our efficient and stable blue quantum dot light-emitting devices can facilitate the development of electroluminescent full-colour displays using quantum dots.

Preparation and characterization of zinc gallate phosphor for electrochemical luminescence

Zinc gallate (ZnGa2O4) phosphor was fabricated by the direct precipitation method (DPM) and solid state reaction method (SSRM). The physicochemical and electrochemical properties of ZnGa2O4 phosphor were investigated using X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV). Finally, the prepared ZnGa2O4 electrode was examined for electrochemical luminescence (ECL). The ZnGa2O4 phosphors showed nano-sized particles at about 10 nm for DPM and 75 nm for SSRM. This electrode showed good conductivity in the reducing hydrogen environment and enhanced luminescence efficiency. The ECL emission intensity of the ZnGa2O4 electrode of DPM was 30 times higher than that of SSRM. This electrode exhibited strong green emission peak intensity of ECL at a wavelength of 520 nm from the excitation of 254 nm wavelength. The nano-sized ZnGa2O4 electrode of DPM led to effective quenching in an ECL study. Therefore, it had a good luminescence stability.

Significantly enhanced luminescence efficiency and thermal stability of BaSi2O2N2:Eu2+ phosphor by doping a very small amount of SiC

Eu2+-activated BaSi2O2N2 oxonitridosilicate phosphor is an efficient cyan compensator to improve the color rendering index of WLEDs for full-spectrum lighting. However, the low luminescent efficiency and poor thermal stability of this type of phosphor severely restrict its practical industry applications. Herein, SiC was proposed into the preparation process of BaSi2O2N2 to enhance the luminescence and thermal stability. Due to the very small amount of SiC addition, the samples of BaSi2O2N2-4x/3Cx:Eu2+ maintain the orthorhombic crystal structure of BaSi2O2N2:Eu2+, but the unit cell volumes and particle sizes become larger. The luminescent intensity reaches the maximum when x = 0.075 and the absorption efficiency and internal quantum efficiency are 67.59% and 58.26%, which are increased by 5.34% and 14.66% relative to the SiC-free sample, respectively. The bandgap and lifetime of Ba0.97Si2O2N1.9C0.075:0.03Eu2+ are calculated to be 2.06 eV and 407.91 ns, respectively. The sample of Ba0.97Si2O2N1.9C0.075:0.03Eu2+ possesses a higher activation energy of 0.383 eV and exhibits a little loss of 13.3% of luminescence intensity at 423 K, which is improved by 11.4% relative to the SiC-free sample. Higher structural stiffness derived from the partially replacement of Si−N bonds by Si-C is supposed as the main reason of the higher thermal stability. The luminescence of Ba0.97Si2O2N1.9C0.075:0.03Eu2+ degrades only by 4.64% in five thermal cycles, which mainly thanks to the improved antioxidant of Eu2+. The Ba0.97Si2O2N1.9C0.075:0.03Eu2+ sample demonstrates an excellent color stability with a tiny chromaticity shift of ~28.19 × 10-3 ranging from 298 to 423 K. A WLED with the cyan-emitting Ba0.97Si2O2N1.9C0.075:0.03Eu2+ exhibits a full spectrum with CRI of 95.1.

Perspective for aggregation-induced delayed fluorescence mechanism: A QM/MM study**Project supported by the National Natural Science Foundation of China (Grant Nos. 11874242, 11974216, and 11904210), Shandong Provincial Natural Science Foundation, China (Grant No. ZR2019MA056), Taishan Scholar Project of Shandong Province, China, and the China Postdoctoral Science Foundation (Grant No. 2018M642689).

To enhance the potential application of thermally activated delayed fluorescence (TADF) molecular materials, new functions are gradually cooperated to the TADF molecules. Aggregation induced emission can effectively solve the fluorescence quenching problem for TADF molecules in solid phase, thus aggregation-induced delayed fluorescence (AIDF) molecules were recently focused. Nevertheless, their luminescent mechanisms are not clear enough. In this work, excited state properties of an AIDF molecule DMF-BP-DMAC [reported in Chemistry–An Asian Journal 14 828 (2019)] are theoretically studied in tetrahydrofuran (THF) and solid phase. For consideration of surrounding environment, the polarizable continuum method (PCM) and the combined quantum mechanics and molecular mechanics (QM/MM) method were applied for solvent and solid phase, respectively. Due to the increase of the transition dipole moment and decrease of the energy difference between the first single excited state (S1) and the ground state (S0), the radiative rate is increased by about 2 orders of magnitude in solid phase. The energy dissipation of the non-radiative process from S1 to S0 is mainly contributed by low-frequency vibrational modes in solvent, and they can be effectively suppressed in aggregation, which may lead to a slow non-radiation process in solid phase. Both factors would induce enhanced luminescence efficiency of DMF-BP-DMAC in solid phase. Meanwhile, the small energy gap between S1 and triplet excited states results in high reverse intersystem crossing (RISC) rates in both solvent and solid phase. Therefore, TADF is confirmed in both phases. Aggregation significantly influences both the ISC and RISC processes and more RISC channels are involved in solid state. The enhanced delayed fluorescence should be induced by both the enhanced fluorescent efficiency and ISC efficiency. Our calculation provides a reasonable explanation for experimental measurements and helps one to better understand the luminescence mechanism of AIDF molecules.

Luminescence efficiency Enhancement for different solar cells designs

Luminescence efficiency Enhancement for different solar cells designs

Charge transfer mediated photoluminescence enhancement in carbon dots embedded in TiO2 nanotube matrix

Carbon quantum dots (CQDs) have drawn a lot of attention in recent years for imaging applications due to their luminescence properties in the visible range. There has been a strong thrust in achieving CQDs with enhanced luminescence efficiency. We report nearly three times increase in the total photoluminescence emission of CQD films by depositing them on TiO2 nanotube (NT) substrates, instead of glass. The net increase in PL arose from higher CQD core emission and the appearance of a strong surface state emission. High-resolution X-ray photoelectron spectroscopy (XPS) was employed to analyze the composition of the CQD surfaces, which confirmed more carboxyl groups on the surface of CQD in the CQD:NT composite. The band alignment of the composite, determined from XPS measurements, favoured carrier transfer from TiO2 NT to CQD. The TiO2 NT, having better surface coverage and wide absorption spectrum, had high absorption cross-section. The efficient transfer of the carriers from NT to CQD is found to be the dominant phenomenon leading to a significant increase in the PL emission intensity.

Dual-Mode Induction of Tunable Circularly Polarized Luminescence from Chiral Metal-Organic Frameworks.

The general approach for fabricating solid-state materials showing circularly polarized luminescence (CPL) is still in its challenge. In this work, chiral metal-organic frameworks (MOFs) with full-color and white-color circularly polarized light emission are firstly achieved through a host-guest emitter-loading strategy. Chiral zeolitic imidazolate frameworks (ZIFs, a class of MOFs) are fabricated by a facile and simple mixed-ligand coassembly pathway. Meantime, achiral dyes, quantum dots (QDs), and upconversion nanoparticles (UCNPs) are easily loaded into the chiral ZIFs during the synthetic process. Size-matched dyes can be solely encapsulated into the chiral cages of ZIF, resulting in induced CPL and enhanced luminescence efficiency in solid-state ZIF⊃dye composites. Large-sized QDs, after embedding into the gap of the ZIF particles, also exhibited intense CPL activity. Furthermore, through modulating the blending ratio of colored dyes or QDs in chiral ZIFs, white light-emitting ZIFs with circular polarization could be constructed in a solid state. In addition, through loading rare earth element-based upconversion nanoparticles (UCNPs) into chiral ZIFs, upconverted CPL (UC-CPL) could be achieved with a high dissymmetry factor (glum). Thus, various achiral luminophores were endowed with CPL upon coupling with chiral ZIFs, which significantly deepened and enlarged the research scope of the chiroptical materials in a solid state.

Enhanced green emission and thermal stability of Ba3Si6O12N2:Eu2+ by Ce3+/P5+-doping: Unity energy transfer, charge compensation and lattice strain release

To optimize luminescence properties of oxonitridosilicate phosphors are extremely necessary for improving lighting quality of white light-emitting diodes (WLEDs). Herein, we designed Ce3+, Eu2+ codoping and P5+↔Si4+ substitution in the presentative Ba3Si6O12N2:Eu2+ green phosphor to realize an enhancement of luminescence efficiency and thermal stability. Rietveld refinement results of Ce3+, Eu2+, P5+-doped Ba3Si6O12N2 (BSON) confirmed the formation of pure trigonal phase (P-3) of Ba3Si6O12N2 and the successful doping of Ce3+, Eu2+, P5+ ions. Ce3+ and Eu2+ ions randomly occupy two Ba crystallographic sites. Interestingly, a near unity energy transfer (ET, ~100%) from Ce3+ ions to Eu2+ ions is observed. Meanwhile, the doping of P5+ ions into BSON also helps improving the luminescence efficiency and thermal stability, which should be attributed to the charge compensation and the relax of lattice strain. In addition, the white light emitting diodes (WLEDs) fabricated by employing P5+-doped BSON: Eu2+ present a better electroluminescence performance than BSON: Eu2+. This study could serve as a guide in developing optimized oxonitridosilicates phosphors with improved luminescence performances based on complete energy transfer and lattice variations in local coordination environments through cation substitutions, and the as-prepared Ce3+/P5+-codoped Ba3Si6O12N2:Eu2+ could be an excellent green-emitting phosphor for UV-to-Visible LED chips pumped WLEDs.

Luminescence enhancement mechanisms of AgInS2/ZnS core/shell nanoparticles fabricated by suppressing quaternary alloying

Nanoparticles of chalcopyrite semiconductors with I–III–VI2 compositions have attracted attention as potential non-toxic alternatives to highly luminescent Cd–chalcogenide semiconductor nanoparticles. Numerous studies have reported that chalcopyrite nanoparticles capped with ZnS shells exhibit enhanced luminescence efficiencies; however, neither the actual core/shell structure nor the origin of the enhanced emission has been explained. Moreover, luminescence enhancement in I–III–VI2 nanoparticles alloyed with Zn (e.g. Zn–Ag–In–S) complicates our understanding of the origin of enhanced luminescence efficiencies in core/shell nanoparticles. In this study, we found the optimal heating condition for fabricating ZnS shells around AgInS2 nanoparticles by suppressing the alloying of the core and shell components. For AgInS2 nanoparticles with an average diameter of 3.4 nm, maximum luminescence enhancement was achieved when ZnS shells were formed at 393 K. Analyses of the carrier recombination mechanisms indicate that the luminescence improvement was due to both passivation of the non-radiative recombination centres on the nanoparticle surfaces by the ZnS shells and the formation of additional radiative recombination centres induced by a slight inclusion of Zn2+ ions in the core/shell interface region. When ZnS coatings were applied at higher temperatures, AgInS2–ZnS alloy nanoparticles formed because of the penetration and diffusion of Zn2+ ions into the nanoparticle bodies followed by the heat-accelerated cation exchange reaction between the Zn2+, Ag+ and In3+ ions. The boundary fabrication temperature between the formation of core/shell nanoparticles and that of alloy nanoparticles was estimated to be 420–430 K.

Uprooting defects to enable high-performance III\u2013V optoelectronic devices on silicon

The monolithic integration of III-V compound semiconductor devices with silicon presents physical and technological challenges, linked to the creation of defects during the deposition process. Herein, a new defect elimination strategy in highly mismatched heteroepitaxy is demonstrated to achieve a ultra-low dislocation density, epi-ready Ge/Si virtual substrate on a wafer scale, using a highly scalable process. Dislocations are eliminated from the epilayer through dislocation-selective electrochemical deep etching followed by thermal annealing, which creates nanovoids that attract dislocations, facilitating their subsequent annihilation. The averaged dislocation density is reduced by over three orders of magnitude, from ~108 cm−2 to a lower-limit of ~104 cm−2 for 1.5 µm thick Ge layer. The optical properties indicate a strong enhancement of luminescence efficiency in GaAs grown on this virtual substrate. Collectively, this work demonstrates the promise for transfer of this technology to industrial-scale production of integrated photonic and optoelectronic devices on Si platforms in a cost-effective way.

Carbazole-Appended Salen-Indium Conjugate Systems: Synthesis and Enhanced Luminescence Efficiency.

Novel carbazole-conjugated salen-In complexes (Cz1 and Cz2) were prepared and fully characterized by 1H and 13C NMR spectroscopy, elemental analysis, and high-resolution mass spectrometry. The major low-energy absorption bands at λabs = 342 nm for Cz1 and 391 nm for Cz2, respectively, are assigned to typical intramolecular charge transfer (ICT) transitions between the carbazole unit and the salen-In center. The solvatochromism effects in various organic solvents and their large Stokes shift distinctly supported the ICT nature. The photoluminescent spectra of Cz1 and Cz2 showed broad emission bands are centered at 459 nm (blue, λex = 354 nm) and 507 nm (green, λex = 396 nm) in THF, respectively, which are typical feature of CT transitions. In particular, Cz1 showed 8-fold enhanced quantum efficiency relative to that of Cz2, at least 10-fold higher than those of the carbazole-free salen-In complexes. Such enhanced luminescence efficiency of Cz1 originated from efficient radiative decay based on the ICT transition between the salen-In moieties and carbazole parts, as well as its structural rigidity in conversion process between the ground (S0) and excited (S1) states. In other words, Cz2 exhibited low quantum yield due to its structural fluctuation, which is free rotation of both the appended carbazole moieties and bridged phenylene rings in conversion between the S0 and S1 structures. Theoretical calculations clearly supported these intriguing results. In addition, these salen-In complexes exhibited high thermal stability (Td5 = 367 °C for Cz1 and 406 °C for Cz2) and electrochemical stability.

Greatly enhanced luminescence efficiency of CdS nanoparticles in aqueous solution

A simple shell-creating technique for the synthesis of CdS nanoparticles covered by ZnS is presented, which also contributes to the understanding of their low quantum yield and luminescence intensity in water, which is usually below 0.01%. The CdS nanoparticles with about 0.8 nm thick ZnS shell were synthesized in a colloidal aqueous solution and stabilized by EDTA. The CdS carrier lifetime and the quantum efficiency is greatly increased. For the latter, values up to 2.7% were achieved. A mechanism for the CdS nanoparticle luminescence in the aqueous solution is proposed, which is based on radiative recombination of charge carriers with structural defects. It was found that the synthesis of CdS in air leads to the inclusion of oxygen atoms in the structure of nanoparticles, which strongly effects the luminescence spectrum. These results show that most of the CdS luminescence centers are localized inside the nanoparticle.

Enhanced luminescence efficiency of GaN:Eu-based light-emitting diodes by localized surface plasmons utilizing gold nanoparticles

We demonstrate the enhancement of luminescence efficiency in GaN:Eu-based light emitting diodes (LEDs) by surface plasmons utilizing gold nanoparticles (NPs). A gold thin film is deposited on a GaN:Eu layer and subsequently thermal-annealed to form gold NPs. The size of the NPs can be controlled by changing the thickness of the films. The room-temperature photoluminescence (PL) intensity of the GaN:Eu LEDs with the NPs increases by 1.42-times compared with those without the NPs when the film thickness is 15 nm, which is attributed to enhanced light extraction efficiency due to coupling with localized surface plasmons. Time-resolved PL spectra at 10 K of the LEDs with the NPs show a shorter lifetime, supporting the existence of the coupling with local surface plasmons. The injection current-light output intensity profiles of the LEDs with the NPs shows 1.3-times enhancement of the output power due to coupling with local surface plasmons.

Enhanced luminescence efficiency of structurally tailored new coumarin-based heterocyclic organic materials: a DFT/TD-DFT study

Recently reported coumarin-biphenyl derivatives by Zhang et al. for luminescent materials have paved the road to tune new structurally tailored coumarin-heterocyclic π-linker-based derivatives (COB) with enhanced luminescence efficiency. Herein, a series of heterocyclic π-linkers (bi-furan, bi-thiophene and bi-pyrrole) have been used to design nine new Donor–π-linker–Donor molecules, and their luminescence efficiency has been evaluated using density functional theory and time-dependent density functional theory calculations and compared with their biphenyl derivatives. Frontier molecular orbital analysis has been carried out to gain insights into the role of different groups towards the HOMO and LUMO of the molecule. The calculated excited-state properties such as absorption and emission spectra have proved their pronounced luminescence efficiency. The lowest singlet–triplet energy gap (ΔEST) confirms their thermally activated delayed fluorescence property. All the newly designed COB compounds have been studied for their charge injection/transport properties such as ionization potential, electron affinity, reorganization energy, hole/electron mobility and their light harvesting efficiency. Overall, the study highlights a fine correlation between the computed luminescence properties and HOMO–LUMO energy gap, which portrays the prominent role of hetero cyclic π-linkers on the photophysical properties of COB derivatives.