Nonradiative States Research Articles

Comparative study on charge photogeneration dynamics of Y small molecule and polymerized Y small molecule based polymer solar cells.

Understanding charge photogeneration processes in polymer solar cells utilizing polymerized Y-molecule acceptors (PYMAs) is of great importance for design and optimization of high-performance solar cells. In this work, excited state dynamics in PYMAs (PYT, PY-DT) and corresponding solar cells were comparably studied with those of Y small molecules (Y5, Y6) by using the steady state and time-resolved spectroscopies as well as time-dependent density functional theory calculation. We find that PYMA (PYT, PY-DT) films exhibit smaller Stokes shifts than that of Y small molecules, indicating a more rigid backbone of PYMAs. Temperature-dependent steady-state PL measurement reveals that compared to small molecule films, the energy barrier from radiative to non-radiative states is smaller in PYMA films. In addition, transient absorption spectroscopy demonstrates that the exciton diffusion process in PYT and PY-DT are mainly intra-chain exciton diffusion mechanism with exciton diffusion coefficients of 1.7 × 10-2 and 2.7 × 10-2cm2s-1, respectively, in contrast with the inter-molecular exciton diffusion in Y5 and Y6 films. For the blend films, the phase sizes of acceptors in PM6:PYT and PM6:PY-DT are determined as 2.3 and 3.3nm, respectively, smaller than that of Y6 (4.7nm) in the PM6:Y6 film. In addition, unlike bimolecular recombination in classical system PM6:Y6, the PYMA-based all-polymer solar cells exhibit geminate type recombination in ultrafast timescale. We find that carrier lifetime plays a critical role in the performance of PYMA-based polymer solar cells. This work provides a comprehensive understanding of the photophysical properties of PYMAs, which is pivotal for designing highly efficient all-polymer solar cells.

Numerical simulation of electromagnetically induced transparency in composite metamaterial

Abstract In high-refractive-index dielectric nanostructure, the Mie resonance become evident, and the destructive interference of the radiation fields from electric and toroidal dipole moments results in the excitation of anapole state, which has the unique optical properties of a dark state and can support the excitation of more diverse optical phenomena, such as the electromagnetically induced transparency (EIT) effect. In this study, we performed numerical simulations of a composite metamaterial consisting of Si nanocubes and gold nanorods. The Au-Si composite structure produces an electromagnetically induced transparency spectrum based on the coupling of the optical dark channel (i. e. anapole state) and bright channel (i. e. localized surface plasmon resonance). By tailoring the surface structure of the dielectric Si cube, the surface charge and current distributions can be modified, and finally, the nonradiative anapole state may be influenced and manipulated. The results show that the modified metal/dielectric metamaterial can realize an electromagnetically induced transparency effect with a transmission of up to 95% and a refractive index sensitivity of 170 nm RIU−1.

Recent progress in high-performance thermally activated delayed fluorescence exciplexes based on multiple reverse intersystem crossing channels

In the field of organic light-emitting diodes (OLEDs), exciplex materials with thermally activated delayed fluorescence (TADF) characteristics have garnered significant attention in recent years owing to their potential for high fluorescence efficiency, primarily achieved through the reverse intersystem crossing (RISC) process. By converting non-radiative triplet states to radiative singlet states, the RISC process can effectively regulate exciton behavior, resulting in the harvest of triplet excitons and the improvement of luminescence efficiency. Recently, multi-RISC strategies have been developed to further enhance the performance of TADF exciplex materials and devices. In this paper, we review these research progress in this area. We classify molecular design strategies according to the composition of exciplexes, discuss the design principles and energy-harvesting mechanism of high-performance TADF exciplexes based on multi-RISC strategies, and prospect their further research and development. The progressive endeavors summarized in this review may inspire further research on material design and device fabrication, and promote the development of OLED applications.

When a Twist Makes a Difference: Exploring PCET and ESIPT on a Nonplanar Hydrogen-Bonded Donor-Acceptor System.

Bioinspired benzimidazole-phenol constructs with an intramolecular hydrogen bond connecting the phenol and the benzimidazole have been synthesized to study both proton-coupled electron transfer (PCET) and excited-state intramolecular proton transfer (ESIPT) processes. Strategic incorporation of a methyl group disrupts the coplanarity between the aromatic units, causing a pronounced twist, weakening the intramolecular hydrogen bond, decreasing the phenol redox potential, reducing the chemical reversibility, and quenching the fluorescence emission. Infrared spectroelectrochemistry and transient absorption spectroscopy confirm the formation of the oxidized product upon PCET and probe excited-state relaxation mechanisms, respectively. Density functional theory calculations of redox potentials corroborate the experimental findings. Additionally, time-dependent density functional theory calculations uncover the fluorescence quenching mechanism, showing that the nonradiative twisted intramolecular charge transfer state responsible for fluorescence quenching is more energetically favorable in the methyl-substituted system. Incorporating groups causing steric hindrance expands the design of biomimetic systems capable of performing both PCET and ESIPT.

Dimethylamine Copper(I) Halide Single Crystals: Structure, Physical Properties, and Scintillation Performance.

Hybrid copper(I) halides have garnered a significant amount of attention as potential substitutes in luminescence and scintillation applications. Herein, we report the discovery and crystal growth of new zero-dimensional compounds, (C2H8N)3Cu2I5 and (C2H8N)4Cu2Br6. The bromide and iodide have a triclinic structure with space group P1̅ and an orthorhombic structure with space group Pnma, respectively. (C2H8N)3Cu2I5 exhibits cyan emission peaking at 504 nm with a photoluminescence quantum yield (PLQY) of 34.79%, while (C2H8N)4Cu2Br6 shows yellowish-green emission peaking at 537 nm with a PLQY of 38.45%. The temperature-dependent photoluminescence data of both compounds were fitted to theoretical models, revealing that nonradiative intermediate states significantly affect thermal quenching and antiquenching. Electron-phonon interactions, the origin of emission line width broadening and peak shifting, were also investigated via fittings. The scintillation properties of (C2H8N)3Cu2I5 were evaluated, and an X-ray imaging device was successfully fabricated using (C2H8N)3Cu2I5. This work demonstrates the potentiality of copper halides in lighting and X-ray imaging applications.

Novel Benzothiadiazole-based Donor-Acceptor Systems: Synthesis, Ultrafast Charge Transfer and Separation Dynamics.

Near-infrared (NIR) absorbing electron donor-acceptor (D-A) chromophores have been at the forefront of current energy research owing to their facile charge transfer (CT) characteristics, which are primitive for photovoltaic applications. Herein, we have designed and developed a new set of benzothiadiazole (BTD)-based tetracyanobutadiene (TCBD)/dicyanoquinodimethane (DCNQ)-embedded multimodular D-A systems (BTD1-BTD6) and investigated their inherent photo-electro-chemical responses for the first time having identical and mixed terminal donors of variable donicity. Apart from poor luminescence, the appearance of broad low-lying optical transitions extendable even in the NIR region (>1000 nm), particularly in the presence of the auxiliary acceptors, are indicative of underlying nonradiative excited state processes leading to robust intramolecular CT and subsequent charge separation (CS) processes in these D-A constructs. While electrochemical studies identify the moieties involved in these photo-events, orbital delocalization and consequent evidence for the low-energy CT transitions have been achieved from theoretical calculations. Finally, the spectral and temporal responses of different photoproducts are obtained from femtosecond transient absorption studies, which, coupled with spectroelectrochemical data, identify broad NIR signals as CS states of the compounds. All the systems are found to be susceptible to ultrafast (~ps) CT and CS before carrier recombination to the ground state, which is, however, significantly facilitated after incorporation of the secondary TCBD/DCNQ acceptors, leading to faster and thus efficient CT processes, particularly in polar solvents. These findings, including facile CT/CS and broad and intense panchromatic absorption over a wide window of the electromagnetic spectrum, are likely to expand the horizons of BTD-based multimodular CT systems to revolutionize the realm of solar energy conversion and associated photonic applications.

Porous PbBr2 films modulation by indium tribromide additive for the fabrication of SnO2-based CsPbBr3 perovskite solar cells

The achievement of complete conversion of PbBr2 films presents a significant challenge in the development of CsPbBr3 films with consistent growth, comprehensive coverage, and controllable components. To address this challenge, introducing a porous structure in the planar PbBr2 film is advantageous for facilitating the immersion of CsBr precursor, thereby reducing impurity phase formation and mitigating strain caused by the film volume expansion. In order to accomplish this, indium tribromide (InBr3) was employed as an additive and the InBr3(DMF)3 adduct was utilized to expedite the release of organic molecules in PbBr2(DMF), resulting in the transformation of planar PbBr2 film into porous structures. The growth orientation of PbBr2 crystals was altered by this transformation, effectively suppressing the generation of metallic Pb impurities in the film. Additionally, it not only optimizes the morphology of CsPbBr3 film but also reduces impurity phase. As a result, the InBr3:CsPbBr3 perovskite solar cell achieved an efficiency of 7.28 %. The majority of In3+ ions were concentrated near the buried interface between SnO2 and InBr3:CsPbBr3, leading to significant improvements in both non-radiative recombination defect states within the perovskite film and electron injection and collection capabilities within the device.

Multi-mode resonance of bound states in the continuum in dielectric metasurfaces

Bound states in the continuum (BIC) represent distinct non-radiative states endowed with infinite lifetime and vanishing resonance linewidth. Introducing asymmetric perturbation to the system can convert true BICs into high quality leaky modes which is useful in many photonic applications. Previously, such perturbation and resonance of interest is only limited to a single factor. However, different perturbations by unit cell gap, geometry and rotation angle result distinctive resonance modes. The combination of two perturbation factors can excite multi-mode resonance contributed from each asymmetric factor which coexist simultaneously; thus, the number of reflectance peaks can be controlled. In addition, we have carefully analyzed the electric field variations under different perturbation factors, followed by a multipolar decomposition of resonances to reveal underlying mechanisms of distinct resonance modes. Through simulations, we find that the introduction of multiple asymmetric perturbations also influences the metasurface sensitivity in refractive index sensing and compare the performance of different resonance modes. These observations provide structural design insights for achieving high quality resonance with multiple modes and ultra-sensitive sensing.

Non-radiative configurations of a few quantum emitters ensembles: Evolutionary optimization approach

Suppressing the spontaneous emission in quantum emitters ensembles (atoms) is one of the topical problems in quantum optics and quantum technology. While many approaches are based on utilizing the subradiance effect in ordered quantum emitters arrays, the ensemble configurations providing the minimal spontaneous emission rate are yet unknown. In this work, we employ the differential evolution algorithm to identify the optimal configurations of a few atomic ensembles that support quantum states with maximal radiative lifetime. We demonstrate that atoms tend to assemble mostly in quasi-regular structures with specific geometry, which strongly depends on the minimally allowed interatomic distance rmin. While the discovered specific non-radiative realizations of small ensembles cannot be immediately predicted, there is particular correspondence to the non-radiative states in the atomic lattices. In particular, we have found that states inheriting their properties either from the bound states in the continuum or band edge states of infinite lattices dominate across a wide range of rmin values. Additionally, we show that for small interatomic distances, the linear arrays with modulated spacing have the smallest radiative losses exponentially decreasing as the size of the ensemble increases.

Charge photogeneration and recombination dynamics in non-fullerene solar cells based on a polymer donor with a mono-fluorinated π-bridge.

Non-symmetric fluorine substitution is an important route for designing π-conjugated polymers for high-performance solar cells. However, excited state dynamics in a non-symmetric fluorinated polymer and solar cells are poorly understood. In this work, excited state dynamics in a neat mono-fluorinated polymer (PTzBI-dF) film and blend films (PTzBI-dF:Y6) were studied using time-resolved spectroscopy. For the neat donor film, we found the activation energy of the PTzBI-dF film transiting from radiative states to non-radiative states to be ∼58 meV. Besides, we found that both exciton diffusion coefficient and exciton diffusion length in the PTzBI-dF film are higher than those in the PTzBI-Cl film, which has no fluorinated π-bridge. The high exciton diffusion length of the PTzBI-dF film benefits from its long exciton lifetime (∼327.8 ps), which is much longer than that of the polymer donors such as P3HT and PM6. For PTzBI-dF:Y6 blend films, we found that the energy level offsets of the HOMO (0.13 eV) and LUMO (0.23 eV) are sufficient to dissociate the acceptor and donor excitons, respectively. Besides, we found that carrier recombination in PTzBI-dF:Y6 and PTzBI-Cl:Y6 blend films are dominated by bimolecular recombination processes, and thermal annealing treatment has a weak influence on the charge photogeneration and recombination process of the PTzBI-dF:Y6 film at an ultrafast time scale. Thus, this work is helpful for understanding photoelectrical conversion processes in non-symmetric fluorinated polymer-based solar cells.

Inverted Lowest Singlet and Triplet Excitation Energy Ordering of Graphitic Carbon Nitride Flakes.

In organic light-emitting diodes (OLEDs), only 25% of electrically generated excitons are in a singlet state, S1, and the remaining 75% are in a triplet state, T1. In thermally activated delayed fluorescence (TADF) chromophores the transition from the nonradiative T1 state to the radiative S1 state can be thermally activated, which improves the efficiency of OLEDs. Chromophores with inverted energy ordering of S1 and T1 states, S1 < T1, are superior to TADF chromophores, thanks to the absence of an energy barrier for the transition from T1 to S1. We benchmark the performance of time-dependent density functional theory using different exchange-correlation functionals and find that scaled long-range corrected double-hybrid functionals correctly predict the inverted singlet-triplet gaps of N-substituted phenalene derivatives. We then show that the inverted energy ordering of S1 and T1 is an intrinsic property of graphitic carbon nitride flakes. A design strategy of new chromophores with inverted singlet-triplet gaps is proposed. The color of emitted light can be fine-tuned through flake size and amine substitution on flake vertices.

Synergistic Defect Passivation and Crystallization Modulation in Efficient Perovskite Solar Cells: The Case of Multifunctional 2-Anisidine-4-Sulfonic Acid.

With the continuous development of the performance of perovskite solar cells, the high-density defects on the perovskite film surface and grain boundaries as well as undesired perovskite crystallization are increasingly emerging as challenges to their commercial application. Herein, a dye intermediate 2-anisidine-4-sulfonic acid (2A4SA), containing sulfonic acid group (SO3-), amino group (-NH2), methoxy group (CH3O-), and benzene ring, which exhibit a synergistic effect in comprehensive defect passivation and crystallization modulation, is incorporated. Detailed investigations show that the SO3- of 2A4SA with high electronegativity firmly chelates with uncoordinated lead ions through the coordination interaction, while the -NH2 and the CH3O- of 2A4SA separately immobilize iodide ions and organic cations in the perovskite lattice through hydrogen bonds, enabling substantially decreased nonradiative recombination and trap state density. Meanwhile, 2A4SA molecules attached to the surface of perovskite nuclei can delay crystallization kinetics and promote preferred vertical growth orientation, thereby attaining the high-crystallinity and large-size-grain perovskite films. Consequently, the 2A4SA-doped device with the structure ITO/SnO2/Cs0.15FA0.75MA0.10PbI3 (2A4SA)/Spiro-OMeTAD/Ag presents a splendid power conversion efficiency (PCE) of 23.06% accompanied by increased open-circuit voltage (1.15 V) and fill factor (82.17%). Furthermore, the optimized film and device demonstrate enhanced long-term stability. The unencapsulated optimized device retains ≈80% of the original PCE after 1000 h upon exposure to ambient atmosphere (20-50% RH), whereas the control group is only 56.8%.

(Invited) Non-Polymer Organic Solar Cells: Microscopic Phonon Control to Suppress Non-Radiative Voltage Loss Via Charge-Separated State

Recent remarkable developments on non-fullerene solar cells have reached photoelectric conversion efficiency (PCE) of 18% by tuning the band energy levels in small molecular acceptors. In this respect, development of the small donor molecule is essential. Although several methods have been applied to elucidate the elementary processes of charge carriers in BHJ-OSCs, mechanistic details of non-radiative voltage loss are poorly understood originating from interfacial heterogeneous electron-hole pairs.A recent time-resolved electron paramagnetic resonance (TREPR) study suggested an impact of the recombination process generating the triplet excitons in non-fullerene acceptor solar cells,[1] while geometries and motions of charge-separated (CS) states were elucidated in details by electron spin polarization (ESP).[2-4] Furthermore, although effects of low-frequency nuclear motions (phonon) on the photocarrier generations have been discussed in several literatures,[2,5,6] microscopic origin of the phonon playing a role on the OPV performance is unclear including impact of the phonon assist on primary recombination processes. Here we systematically investigated mechanisms of solar cell performance with diketopyrrolopyrrole (DPP)–tetrabenzoporphyrin (BP) conjugates of C4-DPP–H2BP and C4-DPP–ZnBP where C4 represents butyl group substituted at the DPP unit as small p-type molecules in non-polymer organic solar cells (OSC) with an acceptor of [6,6]-phenyl-C61-buthylic acid methyl ester. We clarified microscopic origins of the photocarrier caused by phonon-assisted 1D electron-hole dissociations at donor:acceptor interface. Using a time-resolved electron paramagnetic resonance, we have characterized controlled charge-recombination by manipulating disorders in π-π donor stacking, ensuring carrier transport through face-on molecular conformations to suppress non-radiative voltage loss via capturing specific interfacial radical pairs separated by 1.8 nm in bulk-heterojunction solar cells. While disordered lattice motions from the π-π stackings via zinc ligation are essential to enhance the entropy for charge-dissociations at the interface, too much ordered crystallinity causes backscattering phonon to reduce OSC performances.

One-Dimensional Hybrid Copper(I) Iodide Single Crystal with Renewable Scintillation Properties.

Low-dimensional hybrid copper(I) halides attract considerable attention in the field of light emissions. In this work, we obtained the centimeter-sized single crystal of 1,3-propanediamine copper(I) iodide (PDACuI3) with a solvent evaporation method. The single crystal X-ray diffraction of PDACuI3 reveals that the [CuI4] tetrahedra form the corner-connected chains separated by PDAs, forming a one-dimensional structure with an orthorhombic space group of Pbca. The band gap is determined to be 4.03 eV, and the room temperature photoluminescence (PL) quantum yield is determined to be 26.5%. The thermal quenching and negative thermal quenching of emission are observed via temperature-dependent PL spectra, and our study shows that the intermediate nonradiative state below the self-trapped exciton state may get involved in these temperature-dependent behaviors. The X-ray scintillation performance of PDACuI3 single crystals is also evaluated, and the relative light output renewed to 94.3% of the fresh one after a low-temperature annealing. On the basis of our results, PDACuI3 single crystals provide nontoxicity and renewable scintillation performance, thus showing potential application in the area of low-cost radiation detectors.

60Co γ-irradiation of AlGaN UVC light-emitting diodes

270 nm AlGaN UV Light-Emitting Diodes (LEDs) were exposed to 1–5 Mrad fluences of Co-60 γ-rays. The effect of the exposure to radiation was a ∼40% reduction in optical output after the highest fluence. No significant midgap emission was induced in the electro-luminescence spectra of the irradiated LEDs. We ascribe the decrease in optical output to creation of non-radiative states within the active regions. There were small (5–10%) increases in forward and reverse current as a result of irradiation with an effective carrier removal rate of <1 cm−1. The irradiation did not produce any increase in degradation rate of the LEDs output power under high drive current (95 mA) compared to unirradiated devices, which is consistent with the lack of midgap emission. The relatively small changes in electrical and optical properties, along with the resistance of the AlxGa1-xN/AlN to displacement damage effects indicate these devices may be well-suited to harsh terrestrial and space radiation applications.

Conformational effect on the photophysics of two BODIPY dyes in a mixture of butanol and acetonitrile: Insight from the steady-state, fluorescence time-resolved spectroscopy and TD-DFT calculations

We studied the effect of acetonitrile-butanol-1 mixture composition on the photophysics (absorption, fluorescence emission spectra, the quantum yield as well as the relaxation of the excited state) of two BODIPY derivatives with an aryl and pyridine substituent in the meso position and methyl (ethyl) in α,β-position. The behavior of these photophysical properties (fluorescence quantum yields, fluorescence lifetimes, radiative and nonradiative constants) as a function of the mixture composition points to its correlation with the rotation of the phenyl group that is possible in BDP2 while it is hindered in BDP1 as a channel of the excited state energy relaxation. As a consequence, the photophysical properties of BDP1 are weakly dependent on the mixture composition while those of BPD2 undergo two stages of variation. In the low mole fraction of Butanol-1 (lower than 0.48), where the viscosity changes by 0.8 MPa.s, the BDP2 photophysical properties are slightly dependent on the mixture composition. We conjecture that the free rotation of the phenyl group allows both radiative and nonradiative excited state relaxation to occur. This is shown by a relatively high fluorescence quantum yield and nonradiative constant values that remain constant in this range of butanol-1 mol fraction. For its further increase, the photophysical properties become strongly dependent on the change of the mixture composition and this was associated with the gradual increase of the viscosity by a factor of 1.7 MPa.s that results in a hindrance of the rotation of the phenyl group. This makes 8-phenyl substituted BDP2 a sensitive molecular rotor for small changes in viscosity between 0.2 and 3 MPa.s.

High-Q multiple Fano resonances with near-unity modulation depth governed by nonradiative modes in all-dielectric terahertz metasurfaces.

Reducing radiative losses for a high quality factor resonance based on the concept of nonradiative states including anapole mode and bound states in the continuum mode has been attracting extensive attention. However, a high quality factor resonance is obtained at the expense of its modulation depth. Here, an asymmetric metasurfaces structure consisted of silicon double D-shaped resonator arrays that can support both an anapole mode and two bound states in the continuum modes in terahertz band is proposed, which has not only ultrahigh quality factor but also near-unity modulation depth. A resonance derived from anapole mode with stronger electromagnetic field enhancement and higher quality factor can be achieved by increasing the gap of resonator. Meanwhile, two Fano resonances governed by bound states in the continuum modes can be identified, and their quality factors can be easily tailored by controlling the asymmetry of resonator. Such an all-dielectric metasurfaces structure may give access to the development of the terahertz sensors, filters, and modulators.

Vacancy-Mediated Anomalous Emission Characteristics of Size-Confined Semiconducting CoTe2.

Transition-metal tellurides (TMTs) are promising materials for "post-graphene age" nanoelectronics and energy storage applications owing to their industry-standard compatibility, high electron mobility, large spin-orbit coupling (SOC), etc. However, tellurium (Te) having a larger ionic radius (Z = 52) and broader d-bands endows TMTs with semimetallic nature, restricting their application in photonic and optoelectronic domains. In this work, we report the optical properties of the quantum-confined semiconducting phase of cobalt ditelluride (CoTe2) for the first time, exhibiting excellent two-color band photoabsorption attributes covering the UV-visible and near-infrared regions. Furthermore, novel excitonic resonances (X) of size-varying CoTe2 nanocrystals and quantum dots (QDs) are indicated by their temperature-dependent emission characteristics, which are attributed to the splitting of band edge states via confinement. On the other hand, the sudden rupture of the large-area CoTe2 nanosheets via ultrasonication incorporates Co vacancy-mediated localized trap states within the band gap, which is attributed to the superior room-temperature photoluminescence (PL) quantum yield of QDs and further corroborated using Raman analysis and atomistic density functional theory (DFT) simulations. Most interestingly, the excitonic peak of CoTe2 QDs reveals a unique positive-to-negative thermal quenching transition phenomenon, owing to the thermal activation of nonradiative surface trap states. These results introduce an exciting approach for the defect-mediated color-saturated light emission that paves the way for solution-processed telluride-based QD light-emitting diodes.

Imaging Stars with Quantum Error Correction

The development of high-resolution, large-baseline optical interferometers would revolutionize astronomical imaging. However, classical techniques are hindered by physical limitations including loss, noise, and the fact that the received light is generally quantum in nature. We show how to overcome these issues using quantum communication techniques. We present a general framework for using quantum error correction codes for protecting and imaging starlight received at distant telescope sites. In our scheme, the quantum state of light is coherently captured into a nonradiative atomic state via stimulated Raman adiabatic passage, which is then imprinted into a quantum error correction code. The code protects the signal during subsequent potentially noisy operations necessary to extract the image parameters. We show that even a small quantum error correction code can offer significant protection against noise. For large codes, we find noise thresholds below which the information can be preserved. Our scheme represents an application for near-term quantum devices that can increase imaging resolution beyond what is feasible using classical techniques.

Plasmonic anapole metamaterial for refractive index sensing

Electromagnetic anapole mode is a nonradiative state of light originating from the deconstructive interference of radiation of the oscillating electric and toroidal dipole moments. The high quality anapole-related resonances can be used in enhancing nonlinear electromagnetic properties of materials and in sensor applications. In this work, we experimentally demonstrate plasmonic anapole metamaterial sensor of environmental refractive index in the optical part of the spectrum. Our results show that the sensor exhibits high sensitivity to the ambient refractive index at the level of 330 nm/RIU and noise floor of 8.7 × 10-5 RIU. This work will pave the way for applications of anapole metamaterials in biosensing and spectroscopy.