Intermediate-phase engineering via dimethylammonium cation additive for stable perovskite solar cells.

Achieving the long-term stability of perovskite solar cells is arguably the most important challenge required to enable widespread commercialization. Understanding the perovskite crystallization process and its direct impact on device stability is critical to achieving this goal. The commonly employed dimethyl-formamide/dimethyl-sulfoxide solvent preparation method results in a poor crystal quality and microstructure of the polycrystalline perovskite films. In this work, we introduce a high-temperature dimethyl-sulfoxide-free processing method that utilizes dimethylammonium chloride as an additive to control the perovskite intermediate precursor phases. By controlling the crystallization sequence, we tune the grain size, texturing, orientation (corner-up versus face-up) and crystallinity of the formamidinium (FA)/caesium (FA)yCs1-yPb(IxBr1-x)3 perovskite system. A population of encapsulated devices showed improved operational stability, with a median T80 lifetime (the time over which the device power conversion efficiency decreases to 80% of its initial value) for the steady-state power conversion efficiency of 1,190 hours, and a champion device showed a T80 of 1,410 hours, under simulated sunlight at 65 °C in air, under open-circuit conditions. This work highlights the importance of material quality in achieving the long-term operational stability of perovskite optoelectronic devices.

Metal Halide Perovskite Heterostructures: Blocking Anion Diffusion with Single-Layer Graphene.

The development of metal halide perovskite/perovskite heterostructures is hindered by rapid interfacial halide diffusion leading to mixed alloys rather than sharp interfaces. To circumvent this outcome, we developed an ion-blocking layer consisting of single-layer graphene (SLG) deposited between the metal halide perovskite layers and demonstrated that it effectively blocks anion diffusion in a CsPbBr3/SLG/CsPbI3 heterostructure. Spatially resolved elemental analysis and spectroscopic measurements demonstrate the halides do not diffuse across the interface, whereas control samples without the SLG show rapid homogenization of the halides and loss of the sharp interface. Ultraviolet photoelectron spectroscopy, DFT calculations, and transient absorbance spectroscopy indicate the SLG has little electronic impact on the individual semiconductors. In the CsPbBr3/SLG/CsPbI3, we find a type I band alignment that supports transfer of photogenerated carriers across the heterointerface. Light-emitting diodes (LEDs) show electroluminescence from both the CsPbBr3 and CsPbI3 layers with no evidence of ion diffusion during operation. Our approach provides opportunities to design novel all-perovskite heterostructures to facilitate the control of charge and light in optoelectronic applications.

Substrate Analogues for the Enzyme-Catalyzed Detoxification of the Organophosphate Nerve Agents-Sarin, Soman, and Cyclosarin.

The G-type nerve agents, sarin (GB), soman (GD), and cyclosarin (GF), are among the most toxic compounds known. Much progress has been made in evolving the enzyme phosphotriesterase (PTE) from Pseudomonas diminuta for the decontamination of the G-agents; however, the extreme toxicity of the G-agents makes the use of substrate analogues necessary. Typical analogues utilize a chromogenic leaving group to facilitate high-throughput screening, and substitution of an O-methyl for the P-methyl group found in the G-agents, in an effort to reduce toxicity. Till date, there has been no systematic evaluation of the effects of these substitutions on catalytic activity, and the presumed reduction in toxicity has not been tested. A series of 21 G-agent analogues, including all combinations of O-methyl, p-nitrophenyl, and thiophosphate substitutions, have been synthesized and evaluated for their ability to unveil the stereoselectivity and catalytic activity of PTE variants against the authentic G-type nerve agents. The potential toxicity of these analogues was evaluated by measuring the rate of inactivation of acetylcholinesterase (AChE). All of the substitutions reduced inactivation of AChE by more than 100-fold, with the most effective being the thiophosphate analogues, which reduced the rate of inactivation by about 4-5 orders of magnitude. The analogues were found to reliably predict changes in catalytic activity and stereoselectivity of the PTE variants and led to the identification of the BHR-30 variant, which has no apparent stereoselectivity against GD and a kcat/Km of 1.4 × 106, making it the most efficient enzyme for GD decontamination reported till date.

Green MIP-202(Zr) Catalyst: Degradation and Thermally Robust Biomimetic Sensing of Nerve Agents.

Rapid and robust sensing of nerve agent (NA) threats is necessary for real-time field detection to facilitate timely countermeasures. Unlike conventional phosphotriesterases employed for biocatalytic NA detection, this work describes the use of a new, green, thermally stable, and biocompatible zirconium metal-organic framework (Zr-MOF) catalyst, MIP-202(Zr). The biomimetic Zr-MOF-based catalytic NA recognition layer was coupled with a solid-contact fluoride ion-selective electrode (F-ISE) transducer, for potentiometric detection of diisopropylfluorophosphate (DFP), a F-containing G-type NA simulant. Catalytic DFP degradation by MIP-202(Zr) was evaluated and compared to the established UiO-66-NH2 catalyst. The efficient catalytic DFP degradation with MIP-202(Zr) at near-neutral pH was validated by 31P NMR and FT-IR spectroscopy and potentiometric F-ISE and pH-ISE measurements. Activation of MIP-202(Zr) using Soxhlet extraction improved the DFP conversion rate and afforded a 2.64-fold improvement in total percent conversion over UiO-66-NH2. The exceptional thermal and storage stability of the MIP-202/F-ISE sensor paves the way toward remote/wearable field detection of G-type NAs in real-world environments. Overall, the green, sustainable, highly scalable, and biocompatible nature of MIP-202(Zr) suggests the unexploited scope of such MOF catalysts for on-body sensing applications toward rapid on-site detection and detoxification of NA threats.

Overcoming the Challenges of Enzyme Evolution To Adapt Phosphotriesterase for V-Agent Decontamination.

The bacterial enzyme phosphotriesterase (PTE) is noted for its ability to hydrolyze many organophosphate compounds, including insecticides and chemical warfare agents. PTE has been the subject of multiple enzyme evolution attempts, which have been highly successful against specific insecticides and the G-type nerve agents. Similar attempts targeting the V-type nerve agents have failed to achieve the same degree of success. Enzyme evolution is an inherently complex problem, which is complicated by synergistic effects, the need to use analogues in high-throughput screening, and a lack of quantitative data to direct future efforts. Previous evolution experiments with PTE have assumed an absence of synergy and minimally screened large libraries, which provides no quantitative information about the effects of individual mutations. Here a systemic approach has been applied to a 28800-member six-site PTE library. The library is screened against multiple V-agent analogues, and a combination of sequence and quantitative activity analysis is used to extract data about the effects of individual mutations. We demonstrate that synergistic relationships dominate the evolutionary landscape of PTE and that analogue activity profiles can be used to identify variants with high activity for substrates. Using these approaches, multiple variants with kcat/ Km values for the hydrolysis of VX that were improved >1500-fold were identified, including one variant that is improved 9200-fold relative to wild-type PTE and is specific for the SP enantiomer of VX. Multiple variants that were highly active for ( SP)-VR were identified, the best of which has a kcat/ Km values that is improved 13400-fold relative to that of wild-type PTE.

Targeted Ligand-Exchange Chemistry on Cesium Lead Halide Perovskite Quantum Dots for High-Efficiency Photovoltaics.

The ability to manipulate quantum dot (QD) surfaces is foundational to their technological deployment. Surface manipulation of metal halide perovskite (MHP) QDs has proven particularly challenging in comparison to that of more established inorganic materials due to dynamic surface species and low material formation energy; most conventional methods of chemical manipulation targeted at the MHP QD surface will result in transformation or dissolution of the MHP crystal. In previous work, we have demonstrated record-efficiency QD solar cells (QDSCs) based on ligand-exchange procedures that electronically couple MHP QDs yet maintain their nanocrystalline size, which stabilizes the corner-sharing structure of the constituent PbI64- octahedra with optoelectronic properties optimal for solar energy conversion. In this work, we employ a variety of spectroscopic techniques to develop a molecular-level understanding of the MHP QD surface chemistry in this system. We individually target both the anionic (oleate) and cationic (oleylammonium) ligands. We find that atmospheric moisture aids the process by hydrolysis of methyl acetate to generate acetic acid and methanol. Acetic acid then replaces native oleate ligands to yield QD surface-bound acetate and free oleic acid. The native oleylammonium ligands remain throughout this film deposition process and are exchanged during a final treatment step employing smaller cations-namely, formamidinium. This final treatment has a narrow processing window; initial treatment at this stage leads to a more strongly coupled QD regime followed by transformation into a bulk MHP film after longer treatment. These insights provide chemical understanding to the deposition of high-quality, electronically coupled MHP QD films that maintain both quantum confinement and their crystalline phase and attain high photovoltaic performance.

Encapsulation of a Nerve Agent Detoxifying Enzyme by a Mesoporous Zirconium Metal-Organic Framework Engenders Thermal and Long-Term Stability.

Immobilized enzymes typically have greater thermal and operational stability than their soluble form. Here we report that for the first time, a nerve agent detoxifying enzyme, organophosphorus acid anhydrolase (OPAA), has been successfully encapsulated into a water-stable zirconium metal-organic framework (MOF). This MOF features a hierarchical mesoporous channel structure and exhibits a 12 wt % loading capacity of OPAA. The thermal and long-term stabilities of OPAA are both significantly enhanced after immobilization.

Engineering the Organophosphorus Acid Anhydrolase Enzyme for Increased Catalytic Efficiency and Broadened Stereospecificity on Russian VX.

The enzyme organophosphorus acid anhydrolase (OPAA), from Alteromonas sp. JD6.5, has been shown to rapidly catalyze the hydrolysis of a number of toxic organophosphorus compounds, including several G-type chemical nerve agents. The enzyme was cloned into Escherichia coli and can be produced up to approximately 50% of cellular protein. There have been no previous reports of OPAA activity on VR {Russian VX, O-isobutyl S-[2-(diethylamino)ethyl] methylphosphonothioate}, and our studies reported here show that wild-type OPAA has poor catalytic efficacy toward VR. However, via application of a structurally aided protein engineering approach, significant improvements in catalytic efficiency were realized via optimization of the small pocket within the OPAA's substrate-binding site. This optimization involved alterations at only three amino acid sites resulting in a 30-fold increase in catalytic efficiency toward racemic VR, with a strong stereospecificity toward the P(+) enantiomer. X-ray structures of this mutant as well as one of its predecessors provide potential structural rationales for their effect on the OPAA active site. Additionally, a fourth mutation at a site near the small pocket was found to relax the stereospecificity of the OPAA enzyme. Thus, it allows the altered enzyme to effectively process both VR enantiomers and should be a useful genetic background in which to seek further improvements in OPAA VR activity.

Variants of Phosphotriesterase for the Enhanced Detoxification of the Chemical Warfare Agent VR.

The V-type organophosphorus nerve agents are among the most hazardous compounds known. Previous efforts to evolve the bacterial enzyme phosphotriesterase (PTE) for the hydrolytic decontamination of VX resulted in the identification of the variant L7ep-3a, which has a kcat value more than 2 orders of magnitude higher than that of wild-type PTE for the hydrolysis of VX. Because of the relatively small size of the O-ethyl, methylphosphonate center in VX, stereoselectivity is not a major concern. However, the Russian V-agent, VR, contains a larger O-isobutyl, methylphosphonate center, making stereoselectivity a significant issue since the SP-enantiomer is expected to be significantly more toxic than the RP-enantiomer. The three-dimensional structure of the L7ep-3a variant was determined to a resolution of 2.01 Å (PDB id: 4ZST ). The active site of the L7ep-3a mutant has revealed a network of hydrogen bonding interactions between Asp-301, Tyr-257, Gln-254, and the hydroxide that bridges the two metal ions. A series of new analogues that mimic VX and VR has helped to identify critical structural features for the development of new enzyme variants that are further enhanced for the catalytic detoxification of VR and VX. The best of these mutants has been shown to have a reversed stereochemical preference for the hydrolysis of VR-chiral center analogues. This mutant hydrolyzes the two enantiomers of VR 160- and 600-fold faster than wild-type PTE hydrolyzes the SP-enantiomer of VR.

Mn Additive Improves Zr Grain Boundary Diffusion for Sintering of a Y-Doped BaZrO3 Proton Conductor.

Yttrium-doped barium zirconate (BZY) has garnered attention as a protonic conductor in intermediate-temperature electrolysis and fuel cells due to its high bulk proton conductivity and excellent chemical stability. However, the performance of BZY can be further enhanced by reducing the concentration and resistance of grain boundaries. In this study, we investigate the impact of manganese (Mn) additives on the sinterability and proton conductivity of Y-doped BaZrO3 (BZY). By employing a combinatorial pulsed laser deposition (PLD) technique, we synthesized BZY thin films with varying Mn concentrations and sintering temperatures. Our results revealed a significant enhancement in sinterability as Mn concentrations increased, leading to larger grain sizes and lower grain boundary concentrations. These improvements can be attributed to the elevated grain boundary diffusion of zirconium (Zr) cations, which enhances material densification. We also observed a reduction in Goldschmidt's tolerance factor with increased Mn substitution, which can improve proton transport. The high proton conduction of BZY with Mn additives in low-temperature and wet hydrogen environments makes it a promising candidate for protonic ceramic electrolysis cells and fuel cells. Our findings not only advance the understanding of Mn additives in BZY materials but also demonstrate a high-throughput combinatorial thin film approach to select additives for other perovskite materials with importance in mass and charge transport applications.

Minimizing Interfacial Recombination in 1.8 eV Triple-Halide Perovskites for 27.5% Efficient All-Perovskite Tandems.

All-perovskite tandem solar cells show great potential to enable the highest performance at reasonable costs for a viable market entry in the near future. In particular, wide-bandgap (WBG) perovskites with higher open-circuit voltage (VOC ) are essential to further improve the tandem solar cells' performance. Here, a new 1.8 eV bandgap triple-halide perovskite composition in conjunction with a piperazinium iodide (PI) surface treatment is developed. With structural analysis, it is found that the PI modifies the surface through a reduction of excess lead iodide in the perovskite and additionally penetrates the bulk. Constant light-induced magneto-transport measurements are applied to separately resolve charge carrier properties of electrons and holes. These measurements reveal a reduced deep trap state density, and improved steady-state carrier lifetime (factor 2.6) and diffusion lengths (factor 1.6). As a result, WBG PSCs achieve 1.36 V VOC , reaching 90% of the radiative limit. Combined with a 1.26 eV narrow bandgap (NBG) perovskite with a rubidium iodide additive, this enables a tandem cell with a certified scan efficiency of 27.5%.

Enzymatic neutralization of the chemical warfare agent VX: evolution of phosphotriesterase for phosphorothiolate hydrolysis.

The V-type nerve agents (VX and VR) are among the most toxic substances known. The high toxicity and environmental persistence of VX make the development of novel decontamination methods particularly important. The enzyme phosphotriesterase (PTE) is capable of hydrolyzing VX but with an enzymatic efficiency more than 5 orders of magnitude lower than with its best substrate, paraoxon. PTE has previously proven amenable to directed evolution for the improvement of catalytic activity against selected compounds through the manipulation of active-site residues. Here, a series of sequential two-site mutational libraries encompassing 12 active-site residues of PTE was created. The libraries were screened for catalytic activity against a new VX analogue, DEVX, which contains the same thiolate leaving group of VX coupled to a diethoxyphosphate core rather than the ethoxymethylphosphonate core of VX. The evolved catalytic activity with DEVX was enhanced 26-fold relative to wild-type PTE. Further improvements were facilitated by targeted error-prone PCR mutagenesis of loop-7, and additional PTE variants were identified with up to a 78-fold increase in the rate of DEVX hydrolysis. The best mutant hydrolyzed the racemic nerve agent VX with a value of kcat/Km = 7 × 10(4) M(-1) s(-1), a 230-fold improvement relative to wild-type PTE. The highest turnover number achieved by the mutants created for this investigation was 137 s(-1), an enhancement of 152-fold relative to wild-type PTE. The stereoselectivity for the hydrolysis of the two enantiomers of VX was relatively low. These engineered mutants of PTE are the best catalysts ever reported for the hydrolysis of nerve agent VX.

Electrochemical Doping of Halide Perovskites by Noble Metal Interstitial Cations.

Metal halide perovskites are an attractive class of semiconductors, but it has proven difficult to control their electronic doping by conventional strategies due to screening and compensation by mobile ions or ionic defects. Noble-metal interstitials represent an under-studied class of extrinsic defects that plausibly influence many perovskite-based devices. In this work, doping of metal halide perovskites is studied by electrochemically formed Au+ interstitial ions, combining experimental data on devices with a computational analysis of Au+ interstitial defects based on density functional theory (DFT). Analysis suggests that Au+ cations can be easily formed and migrate through the perovskite bulk via the same sites as iodine interstitials (Ii + ). However, whereas Ii + compensates n-type doping by electron capture, the noble-metal interstitials act as quasi-stable n-dopants. Experimentally, voltage-dependent, dynamic doping by current density-time (J-t), electrochemical impedance, and photoluminescence measurements are characterized. These results provide deeper insight into the potential beneficial and detrimental impacts of metal electrode reactions on long-term performance of perovskite photovoltaic and light-emitting diodes, as well as offer an alternative doping explanation for the valence switching mechanism of halide-perovskite-based neuromorphic and memristive devices.

Enzymes for the homeland defense: optimizing phosphotriesterase for the hydrolysis of organophosphate nerve agents.

Phosphotriesterase (PTE) from soil bacteria is known for its ability to catalyze the detoxification of organophosphate pesticides and chemical warfare agents. Most of the organophosphate chemical warfare agents are a mixture of two stereoisomers at the phosphorus center, and the S(P)-enantiomers are significantly more toxic than the R(P)-enantiomers. In previous investigations, PTE variants were created through the manipulation of the substrate binding pockets and these mutants were shown to have greater catalytic activities for the detoxification of the more toxic S(P)-enantiomers of nerve agent analogues for GB, GD, GF, VX, and VR than the less toxic R(P)-enantiomers. In this investigation, alternate strategies were employed to discover additional PTE variants with significant improvements in catalytic activities relative to that of the wild-type enzyme. Screening and selection techniques were utilized to isolate PTE variants from randomized libraries and site specific modifications. The catalytic activities of these newly identified PTE variants toward the S(P)-enantiomers of chromophoric analogues of GB, GD, GF, VX, and VR have been improved up to 15000-fold relative to that of the wild-type enzyme. The X-ray crystal structures of the best PTE variants were determined. Characterization of these mutants with the authentic G-type nerve agents has confirmed the expected improvements in catalytic activity against the most toxic enantiomers of GB, GD, and GF. The values of k(cat)/K(m) for the H257Y/L303T (YT) mutant for the hydrolysis of GB, GD, and GF were determined to be 2 × 10(6), 5 × 10(5), and 8 × 10(5) M(-1) s(-1), respectively. The YT mutant is the most proficient enzyme reported thus far for the detoxification of G-type nerve agents. These results support a combinatorial strategy of rational design and directed evolution as a powerful tool for the discovery of more efficient enzymes for the detoxification of organophosphate nerve agents.

Gradient Doping in Sn-Pb Perovskites by Barium Ions for Efficient Single-Junction and Tandem Solar Cells.

Narrow-bandgap (NBG) tin (Sn)-lead (Pb) perovskites generally have a high density of unintentional p-type self-doping, which reduces the charge-carrier lifetimes, diffusion lengths, and device efficiencies. Here, a p-n homojunction across the Sn-Pb perovskite is demonstrated, which results from a gradient doping by barium ions (Ba2+ ). It is reported that 0.1 mol% Ba2+ can effectively compensate the p-doping of Sn-Pb perovskites or even turns it to n-type without changing its bandgap. Ba2+ cations are found to stay at the interstitial sites and work as shallow electron donor. In addition, Ba2+ cations show a unique heterogeneous distribution in perovskite film. Most of the barium ions stay in the top 600 nm region of the perovskite films and turn it into weakly n-type, while the bottom portion of the film remains as p-type. The gradient doping forms a homojunction from top to bottom of the perovskite films with a built-in field that facilitates extraction of photogenerated carriers, resulting in an increased carrier extraction length. This strategy enhances the efficiency of Sn-Pb perovskite single-junction solar cells to over 21.0% and boosts the efficiencies of monolithic perovskite-perovskite tandem solar cells to 25.3% and 24.1%, for active areas of 5.9 mm2  and 0.94 cm2 , respectively.

Compositional texture engineering for highly stable wide-bandgap perovskite solar cells.

The development of highly stable and efficient wide-bandgap (WBG) perovskite solar cells (PSCs) based on bromine-iodine (Br-I) mixed-halide perovskite (with Br greater than 20%) is critical to create tandem solar cells. However, issues with Br-I phase segregation under solar cell operational conditions (such as light and heat) limit the device voltage and operational stability. This challenge is often exacerbated by the ready defect formation associated with the rapid crystallization of Br-rich perovskite chemistry with antisolvent processes. We combined the rapid Br crystallization with a gentle gas-quench method to prepare highly textured columnar 1.75-electron volt Br-I mixed WBG perovskite films with reduced defect density. With this approach, we obtained 1.75-electron volt WBG PSCs with greater than 20% power conversion efficiency, approximately 1.33-volt open-circuit voltage (Voc), and excellent operational stability (less than 5% degradation over 1100 hours of operation under 1.2 sun at 65°C). When further integrated with 1.25-electron volt narrow-bandgap PSC, we obtained a 27.1% efficient, all-perovskite, two-terminal tandem device with a high Voc of 2.2 volts.

Low-energy room-temperature optical switching in mixed-dimensionality nanoscale perovskite heterojunctions.

Long-lived photon-stimulated conductance changes in solid-state materials can enable optical memory and brain-inspired neuromorphic information processing. It remains challenging to realize optical switching with low-energy consumption, and new mechanisms and design principles giving rise to persistent photoconductivity (PPC) can help overcome an important technological hurdle. Here, we demonstrate versatile heterojunctions between metal-halide perovskite nanocrystals and semiconducting single-walled carbon nanotubes that enable room-temperature, long-lived (thousands of seconds), writable, and erasable PPC. Optical switching and basic neuromorphic functions can be stimulated at low operating voltages with femto- to pico-joule energies per spiking event, and detailed analysis demonstrates that PPC in this nanoscale interface arises from field-assisted control of ion migration within the nanocrystal array. Contactless optical measurements also suggest these systems as potential candidates for photonic synapses that are stimulated and read in the optical domain. The tunability of PPC shown here holds promise for neuromorphic computing and other technologies that use optical memory.

Textile-based wearable solid-contact flexible fluoride sensor: Toward biodetection of G-type nerve agents.

Rising global concerns posed by chemical and biological threat agents highlight the critical need to develop reliable strategies for the real-time detection of such threats. While wearable sensing technology is well suited to fulfill this task, the use of on-body devices for rapid and selective field identification of chemical agents is relatively a new area. This work describes a flexible printed textile-based solid-contact potentiometric sensor for the selective detection of fluoride anions liberated by the biocatalytic hydrolysis of fluorine-containing G-type nerve agents (such as sarin or soman). The newly developed solid-contact textile fluoride sensor relies on a fluoride-selective bis(fluorodioctylstannyl)methane ionophore to provide attractive analytical performance with near-Nernstian sensitivity and effective discrimination against common anions, along with excellent reversibility and repeatability for dynamically changing fluoride concentrations. By using stress-enduring printed inks and serpentine structures along with stretchable textile substrates, the resulting textile-based fluoride sensor exhibits robust mechanical resiliency under severe mechanical strains. Such realization of an effective textile-based fluoride-selective electrode allowed biosensing of the nerve-agent simulant diisopropyl fluorophosphate (DFP), in connection to immobilized organophosphorus acid anhydrolylase (OPAA) or organophosphorus hydrolase (OPH) enzymes. A user-friendly portable electronic module transmits data from the new textile-based potentiometric biosensor wirelessly to a nearby smartphone for alerting the wearer instantaneously about potential chemical threats. While expanding the scope of wearable solid-contact anion sensors, such a textile-based potentiometric fluoride electrode transducer offers particular promise for effective discrimination of G-type neurotoxins from organophosphate (OP) pesticides, toward specific field detection of these agents in diverse defense settings.

Chiral-induced spin selectivity enables a room-temperature spin light-emitting diode.

In traditional optoelectronic approaches, control over spin, charge, and light requires the use of both electrical and magnetic fields. In a spin-polarized light-emitting diode (spin-LED), charges are injected, and circularly polarized light is emitted from spin-polarized carrier pairs. Typically, the injection of carriers occurs with the application of an electric field, whereas spin polarization can be achieved using an applied magnetic field or polarized ferromagnetic contacts. We used chiral-induced spin selectivity (CISS) to produce spin-polarized carriers and demonstrate a spin-LED that operates at room temperature without magnetic fields or ferromagnetic contacts. The CISS layer consists of oriented, self-assembled small chiral molecules within a layered organic-inorganic metal-halide hybrid semiconductor framework. The spin-LED achieves ±2.6% circularly polarized electroluminescence at room temperature.