Low Exciton Binding Energy Research Articles

Diketopyrrolopyrrole-triggered low exciton binding energy in D-A covalent organic framework for enhanced uranyl photoreduction

Construction of donor–acceptor covalent organic framework (D-A COFs) photocatalysts is regarded as promising path to promote photocatalytic reduction of uranium, but faces greater challenge due to high exciton binding energies (Eb). In this work, we construct a D-A COF (named Py-DPP-COF) with dye diketopyrrolopyrrole (DPP) unit as acceptor to minimize the Eb (56.5 meV). Importantly, experimental and computational studies reveal that DPP unit as adsorption and photocatalytic active sites play a pivotal role for catalyzing photoreduction of UVI to UIV. The Py-DPP-COF not only broadens the visible light absorption and promotes charge transfer, but also enhances interfacial mass transfer, achieving a higher uranium extraction capacity of 903.6 mg g−1. To our knowledge, this is the first application of DPP-based COFs for photocatalytic reduction of uranium, which greatly inspires the exploration of novel COFs photocatalysts for photo-induced radionuclide removal.

Solution‐Processed Tin‐Antimony Quaternary Chalcohalides for Self‐Powered Broadband Photodetectors

The mixed‐metal quaternary chalcohalides of group IV and V elements are a promising class of low‐toxicity perovskite‐inspired materials with tunable bandgaps and desirable defect tolerance. Sn2SbS2I3 is known for its broadband absorption, low exciton binding energy, ambient stability, and solution processability in thin films. However, its use in optoelectronic devices has so far been only limited to solar cells. In this work, the first self‐powered photodetectors based on Sn2SbS2I3 thin films, sandwiched in an n–i–p device configuration are reported. The insertion of an interlayer at the hole‐transport layer/gold top‐electrode interface reduces the dark current and improves the device performance. The high external quantum efficiency of the devices in the range of 350−900 nm hints to a broadband spectral photoresponsivity. The devices indeed exhibit promising photodetection properties, namely a photoresponsivity of 0.33 A W−1, a specific detectivity of 1.55 × 1012 Jones, and photoresponse/decay times of 0.52 and 0.45 s at zero bias voltage. These results, combined with the excellent operational stability of the photodetectors, encourage the exploration of a wide range of practical light‐sensing applications for quaternary chalcohalides and stimulate device and material engineering to further enhance photodetection across the UV‐Visible‐NIR spectrum.

Engineering exciton dissociation and intermolecular charge transfer to boost superoxide radical in conjugated microporous polymers for simultaneous elimination of coexisting contaminants

Simultaneous photocatalytic elimination of coexisting contaminants with polymeric semiconductors are highly urgent for environmental purification. Nevertheless, the insufficient exciton dissociation and charge transfer in polymeric photocatalysts results in unsatisfactory photocatalytic performance. Herein, we proposed a sulfur-contained linkages engineering strategy via regulating donor–acceptor interactions to boost exciton dissociation and intermolecular charge transfer for efficient generation of superoxide radical. With the low exciton binding energy (50.11 meV) and short average lifetime (τavg‑TAS) of the photoinduced exciton (478.1 ps), the resultant BDT-Tr deriving from BDT and 2,4,6-tris(4-bromophenyl)-1,3,5-triazine exhibited efficient exciton dissociation and charge transfer, enabling superior photocatalytic degradation of ofloxacin (∼94.0 % in 2 h) than that of TTP-Tr (∼87 %) and DTT-Tr (∼76 %) when coupled with the uranium (VI) reduction (∼96.0 % in 1 h). This is the first work highlights the photocatalytic removal of coexisting aqueous pollutants with CMPs-based photocatalysts, which might facilitate the exploration of polymeric semiconductors for wastewater purification.

Ultrahigh carrier mobility and anisotropy of the layered semiconductor ATiN2 (A = Ca, Sr and Ba)

Semiconductors with a suitable band gap and high carrier mobility are highly desirable in the electronics, optoelectronic and photovoltaic applications. The mechanical, electronic, optical and transport properties of the layered nitrides ATiN2 (A = Ca, Sr, and Ba) have been systematically studied by theoretical calculations. These nitrides show good ductility with moderate moduli, larger Poisson's ratio than 0.26 and Pugh's modulus ratio exceeding 1.75. CaTiN2 and SrTiN2 are direct bandgap semiconductors, while BaTiN2 is an indirect bandgap semiconductor, showing suitable band gaps (1.54–1.78 eV) and band edge positions for optoelectronic and photocatalytic water-splitting applications. More intriguingly, they possess superhigh carrier mobility with remarkable anisotropy. Particularly, the in-plane electron mobility reaches an ultrahigh order of 104 cm2V−1s−1, whereas those along the out-of-plane direction are almost zero. In addition, the hole mobilities are also very large along the in-plane direction and the anisotropic ratios are as high as about 30 for all these nitrides. Furthermore, these ATiN2 nitrides exhibit high optical absorption coefficients (∼105 cm−1) and lower exciton binding energies. Due to the suitable band gaps and band alignments, ultrahigh carrier mobility and huge anisotropy, excellent visible light absorption performance, the ATiN2 nitrides will be promising candidate semiconductors in electronics, optoelectronic, photovoltaic and photocatalytic applications.

Facilitating exciton dissociation in conjugated microporous polymers for photocatalytic degradation of tetracycline via a gradient N doping strategy

As a leading green wastewater treatment technology, organic semiconductor photocatalysis for tetracycline (TC) degradation is widely recognized but currently constrained by excessive exciton binding energies and rapid charge recombination. In this work, conjugated microporous polymers (CMPs) with five-membered heterocyclic ring have been fabricated by gradient doping of nitrogen at the monomer level. It demonstrates satisfactory photocatalytic performance, with thiadiazole introduced into the unit, achieving a TC removal rate of 95.6% within 30 min under visible light. The underlying origin of the preferable property lies in the lower exciton binding energy (Eb) with the assistance of the donor–acceptor (D-A) structure constructed by thiadiazole monomer and triazine skeleton. Density Functional Theory (DFT) calculations reveal that this five-membered heterocyclic structure can appropriately regulate the local charge distribution and increase the dipole moment, thus accelerating the migration dynamics of charge carriers in the degradation process. This study provides a novel insight into the modulation of polymer exciton Eb and enlightens the designation of metal-free photocatalysts based on antibiotic degradation.

Front Cover: Steric hindrance induced low exciton binding energy enables low‐driving‐force organic solar cells

Front Cover: Steric hindrance induced low exciton binding energy enables low‐driving‐force organic solar cells

High-performing organic/quantum dot hybrid upconversion device based on a single-component near-infrared-sensitive layer

A donor/acceptor (D/A) heterojunction with an interfacial energetic offset is demonstrated to enable efficient exciton dissociation in organic photodetectors and upconversion devices (UCDs). Unfortunately, this approach usually encounters complicated optimization procedures and interfacial instability. Herein, we present an alternative strategy for achieving high-performing UCDs by utilizing an organic single-component near-infrared (NIR)-sensitive layer instead of a D/A heterojunction. The showcased UCD is constructed by vertically stacking an organic single-component Y6 NIR-detection unit and a quantum dot light-emitting unit. Due to the high dielectric constant and low exciton binding energy of the non-fullerene acceptor Y6, free carriers are directly and spontaneously generated upon NIR light excitation. As a result, the single-component UCD achieves a low light detection capability of 2.5 μW/cm2, a fast refresh rate of >3.8 × 104, and a high resolution exceeding 1100 dpi, providing a stable optical response to high-frequency NIR signals and high-quality NIR imaging.

Comprehensive study on structural, electronic, optical, elastic, and transport properties of natural mercury sulphohalides via DFT computation

The Mercury Sulphohalides have attracted significant attention in the fields of solar cells and thermoelectric applications. This study delves into the fundamental characteristics, including structural, elasticity, electronic behavior, phonon stability, optical properties, and transport features of AgHgSZ (Z = Br, I) through computational simulations based on Density Functional Theory (DFT) using WIEN2k software. Meticulous calculations of the phonon band structure ensure dynamic stability. The semiconductor nature with indirect band gaps (1.833 eV and 1.832 eV) for Mercury Sulphohalides (Br, I), as revealed by their band structures, suggests diverse photovoltaic and transport applications. Mechanical assessments show stable ductility for AgHgSBr and brittleness for AgHgSI, along with anisotropy and resistance to scratching. Optical properties exhibit anisotropy and significant UV absorption. Analysis of effective masses, exciton binding energy, and exciton Bohr radius suggests low exciton binding energy and classification under Mott-Wannier excitons. Positive thermopower results indicate holes as the predominant charge carriers in AgHgSBr and AgHgSI materials. Moreover, essential thermoelectric factors are examined, revealing the compounds’ potential for thermoelectric applications. Notably, the figure of merit (ZT) at 300 K for AgHgSBr and AgHgSI are calculated to be 0.41 and 0.13, respectively. While these values are low at 300 K, they indicate promising potential for thermoelectric applications at higher temperatures. In summary, this investigation provides valuable understanding into the photovoltaic and thermoelectric properties of AgHgSZ (Z = Br, I) materials, potentially paving the way for further exploration in this domain.

(Invited) Realizing the Lowest Bandgap and Exciton Binding Energy in a Two-Dimensional Lead Halide System

3-dimensional hybrid halide perovskites have been intensely researched because of their extraordinary optoelectronic properties with spectacular quantum efficiencies arising primarily from their suitable bandgaps to harvest the solar spectrum, low excitonic binding energies, and low-cost synthetic processes. However, stabilizing these materials under real-life operating conditions has proven to be a challenge, leading to extensive explorations of lower dimensional analogous hybrid halide materials that are often more stable, though generally having considerably higher bandgaps and excitonic binding energies. I shall present some of our investigations leading to the synthesis of a highly moisture-stable 2-dimensional hybrid lead halide material with the lowest bandgap and exciton binding energy within this class of compounds.1 I shall detail the origin of such a low bandgap and exciton binding energy, identifying the most critical control parameters to determine these properties. In addition, I shall also present preliminary results to suggest the beneficial impacts of incorporating the same organic ligand while making a solar photovoltaic device based on three-dimensional hybrid lead halide perovskites.Reference: Debasmita Pariari, Sakshi Mehta, Sayak Mandal, Arup Mahata, Titas Pramanik, Sujit Kamilya, Arya Vidhan, Tayur N. Guru Row, Pralay K. Santra, Shaibal K. Sarkar, Filippo De Angelis, Abhishake Mondal, and D. D. Sarma, Realizing the Lowest Bandgap and Exciton Binding Energy in a Two-Dimensional Lead Halide System, J. Am. Chem. Soc. 145, 15896 (2023).

Molecular engineering push-pull structural versatility in the triphenylamine-thienodioxine-based hole transporting materials for high-performance organic and perovskite solar cells

This study proposes a push-pull molecular engineering approach to fabricate versatile hole-transporting materials (HTMs) for photovoltaic cells. Herein, we introduce a D-π-A strategy for fabricating four highly functional small molecules of thienodioxine core-based HTMs (CJ06C1 to CJ06C4), via core functionalization with diversified electron-withdrawing acceptor moieties. The engineered HTMs are evaluated by employing quantum calculations to analyze the structure-property relationships from optoelectronic, electrochemical, and solvability attributes. The findings reveal that acceptor-integrated HTMs unveil excellent band alignment with active perovskite layer with deeper HOMO energy levels (-4.96 eV to 5.02 eV), transparency in the visible portion λmaxabs<521, which entail appropriate photophysical attributes. In comparison to the reference HTM (CJ06), the acceptor-integrated HTMs have exhibited potentially higher hole mobility rate, accredited to smaller hole reorganization energies (0.15 eV to 0.21 eV), greater transfer integral values (0.26 eV to 0.31 eV) and greater hole hopping rates (1.08×1028 S−1 to 3.70×1028 S−1). The electron-excitation investigation exhibited stronger electronic coupling, smaller hole-electron spatial overlapping, and higher charge transference length (19.42 Å to 21.14 Å) in the fabricated HTMs. Thus ensued a significant upsurge in intrinsic charge transference (74.22–99.74 %) and lower exciton binding energies, leading to easy charge dissociation and low recombination chances compared to the parent HTM (CJ06C1). Moreover, the findings from dipole moments (12.56 D to 13.05 D) and solvation-free energy (-91.08 kJ/mol) to −108.1 kJ/mol),imply easier processability and aptness for film formation. Overall, this study ensures the efficiency of thienodioxine core functionalization with acceptor moieties for fabricating state-of-the-art HTMs. The promising attributes of fabricated HTMs pave the way for forthcoming perovskite solar cells.

Lattice Manipulation with Di-Tertiary Ammonium Spacer in Bismuth Bromide Perovskite Directs Efficient Charge Transport and Suppressed Ion Migration for Photodetector Applications.

Bismuth halide hybrid perovskites have emerged as promising alternatives to their lead halide homologs because of high chemical stability, low toxicity, and structural diversity. However, their advancements in optoelectronic field are plagued with poor charge transport, due to considerable microstrain triggered by bulky spacer. Herein, the di-tertiary ammonium spacer (N,N,N',N'-tetramethyl-1,4-butanediammonium, TMBD) is explored to direct stable 1D bismuth bromide lattice structure with relaxed microstrain. Compared to the primary pentamethylenediamine (PD)2+, the (TMBD)2+ adopting alternating alignment enables a unique H-bonds mode to distort the configuration of inorganic layers to form corner-sharing [BiBr5] near-regular chains with narrower bandgap, lower exciton binding energy, and reduced carrier-lattice interactions, thereby facilitating charge-carrier transport. Moreover, the (TMBD)2+ spacers largely suppress ion migration in perovskite lattice, as substantiated by the experimental and theoretical investigations. Consequently, (TMBD)BiBr5 single crystal photodetector delivers a 185-fold increase in current on/off ratio with respect to (PD)BiBr5 under white light irradiation, considerable responsivity (≈82.97mA W-1), detectivity (≈8.06 ×1011 Jones) under weak light (0.02mW cm-2) irradiation, in the top rank of the reported hybrid bismuth halide perovskites. This finding offers novel design criterion for high-performance lead-free perovskites.

Design of organic electronic materials with lower exciton binding energy: machine learning analysis and high-throughput screening

Design of organic electronic materials with lower exciton binding energy: machine learning analysis and high-throughput screening

Photon–carrier–spin coupling in a one-dimensional Ni(II)-doped ZnTe nanostructure

Transition metal (TM) ion doping in II–VI semiconductors can produce exciton magnetic polarons (EMPs) and localized EMPs containing longitudinal optical (LO) phonon coupling, which will be discussed in this paper. TM ion doping in II–VI semiconductors for a dilute magnetic semiconductor show emission via magnetic polarons (MPs) together with hot carrier effects that need to be understood via its optical properties. The high excitation power that is responsible for hot carrier effects suppresses the charge trapping effect in low exciton binding energy (8.12 meV) semiconductors, even at room temperature (RT). The large polaron radius exhibits strong interaction between the carrier and MP, resulting in anharmonicity effects, in which the side-band energy overtone to LO phonons. The photon-like polaritons exhibit polarized spin interactions with LO phonons that show strong spin–phonon polaritons at RT. The temperature-dependent photoluminescence spectra of Ni-doped ZnTe show free excitons (FX) and FXs interacting with 2LO phonon–spin interactions, corresponding to 3T1(3F) → 1T1(1G) and EMP peaks with ferromagnetically coupled Ni ions at 3T1(3F) → 1E(1G). In addition, other d–d transitions of single Ni ions (600–900 nm) appear at the low-energy side. RT energy shifts of 14–38 meV are observed due to localized states with density-of-states tails extending far into the bandgap-related spin-induced localization at the valence band. These results show spin–spin magnetic coupling and spin–phonon interactions at RT that open up a more realistic new horizon of optically controlled dilute magnetic semiconductor applications.

Quantum-Confined Perovskite Nanocrystals Enabled by Negative Catalyst Strategy for Efficient Light-Emitting Diodes.

The perovskite nanocrystals (PeNCs) are emerging as a promising emitter for light-emitting diodes (LEDs) due to their excellent optical and electrical properties. However, the ultrafast growth of PeNCs often results in large sizes exceeding the Bohr diameter, leading to low exciton binding energy and susceptibility to nonradiative recombination, while small-sized PeNCs exhibit a large specific surface area, contributing to an increased defect density. Herein, Zn2+ ions as a negative catalyst to realize quantum-confined FAPbBr3 PeNCs with high photoluminescence quantum yields (PL QY) over 90%. Zn2+ ions exhibit robust coordination with Br- ions is introduced, effectively retarding the participation of Br- ions in the perovskite crystallization process and thus facilitating PeNCs size control. Notably, Zn2+ ions neither incorporate into the perovskite lattice nor are absorbed on the surface of PeNCs. And the reduced growth rate also promotes sufficient octahedral coordination of PeNC that reduces defect density. The LEDs based on these optimized PeNCs exhibits an external quantum efficiency (EQE) of 21.7%, significantly surpassing that of the pristine PeNCs (15.2%). Furthermore, the device lifetime is also extended by twofold. This research presents a novel approach to achieving high-performance optoelectronic devices.

Tuning the photovoltaic potential of thiazole based materials via incorporation of selenophene and electron acceptors rings at peripheral positions: A DFT approach

The non-fullerene acceptor (NFA) chromophores have sparked scientific and economic interest, due to their rapid advancements in power conversion efficiencies. Therefore, a series of new chlorothiazole based compounds (STM1-STM6) with A1–π–A2–π–A1 configuration was designed using reference chromophore (STMR). Structural modifications were made via incorporating selenophene and extended acceptor units, to enhance photovoltaic response in the designed materials. Density functional theory/time dependent-density functional theory (DFT/TD-DFT) calculations were executed at M06/6-311G (d,p) level to investigate key electronic and photovoltaic properties of STM1-STM6. So, various analyses such as UV–Visible, frontier molecular orbitals (FMOs), transition density matrix (TDM), density of states (DOS), open circuit voltage (Voc) and binding energy (Eb) were conducted to comprehend the photovoltaic properties. The designing in structural aspects with terminal acceptors and π-linker induced a reduction in energy gaps (ΔE = 2.078–2.237 eV) with an enhancement in the bathochromic shift (λmax = 744.650–798.250 nm in chloroform) than reference compound. A higher exciton dissociation rate was observed in all the compounds due to lower binding energy values (Eb = 0.525–0.572 eV). Additionally, TDM and DOS findings further endorsed the effective charge delocalization from HOMO to LUMO. Among all the examined compounds, STM3 exhibited the smallest band gap (2.078 eV), highest absorption maxima (798.250 nm), and the lowest exciton binding energy (0.525 eV), indicating significant electronic properties. Moreover, Voc analysis was conducted with respect to HOMOPBDBT-LUMOacceptor for all the designed chromophores; consequently, STM2 demonstrated a substantial Voc value of 1.647 V. Similarly, electron hole analysis was also conducted and significant electron and hole density was observed in all the investigated compounds, especially in STM2. The entitled compounds with photovoltaic potential would be considered as promising materials for the development of solar energy devices.

DFT-assisted design of curcumin-based donor-π-bridge-acceptor molecular structures: Advancing nonlinear optical materials and sustainable organic solar cells

This study explores the theoretical design of novel curcumin-based structures with enhanced nonlinear optical (NLO) characteristics. By systematically substituting hydroxyl (OH) functionalities in bisdemethoxycurcumin (BdMC) with various donor and acceptor functionalities at the edges of the π-bridge backbone, we constructed 12 different derivatives. Density-functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed at the B3LYP/6-311++G(d,p) and CAM-B3LYP/6-311++G(d,p) levels to analyze the optoelectronic properties. The introduction of donors and acceptors significantly improved NLO characteristics. Notably, BdMC-1 (N(C2H5)2-π-bridge-NO2) exhibited a remarkable enhancement in NLO responses, with the average polarizability (<α>) and the first hyperpolarizability (βtot) increasing from 465.3 to 660.9 (a.u.) and 14254.4 to 143487.6 (a.u.), respectively. UV–Vis spectroscopy showed BdMC-1 as the most red-shifted compound, with a maximum wavelength (λmax) of 431.1 nm, the lowest optical bandgap of 2.88 eV, and an ultrahigh light harvesting efficiency (LHE) of 97.4%. The designed compounds exhibited narrower HOMO-LUMO electronic bandgaps (as low as 2.08 eV) compared to BdMC (3.32 eV), contributing to the improved NLO responses. Natural bond orbital (NBO) analysis confirmed the formation of a charge separation state, facilitating effective electron migration from donors to acceptors through the π-bridge. Additionally, using BdMC-based materials as acceptors in organic solar cells (OSCs) yielded open-circuit voltages (Voc) from 1.62 to 2.23 V, fill factors (FF) above 90%, and low exciton binding energies (Ee−b) in the range of 0.08 to 0.80 eV.

Microwave Assisted Fast Synthesis of a Donor‐Acceptor COF Towards Photooxidative Amidation Catalysis

AbstractThe synthesis of covalent organic frameworks (COFs) at bulk scale require robust, straightforward, and cost‐effective techniques. However, the traditional solvothermal synthetic methods of COFs suffer low scalability as well as requirement of sensitive reaction environment and multiday reaction time (2–10 days) which greatly restricts their practical application. Here, we report microwave assisted rapid and optimized synthesis of a donor‐acceptor (D−A) based highly crystalline COF, TzPm‐COF in second (10 sec) to minute (10 min) time scale. With increasing the reaction time from seconds to minutes crystallinity, porosity and morphological changes are observed for TzPm‐COF. Owing to visible range light absorption, suitable band alignment, and low exciton binding energy (Eb=64.6 meV), TzPm‐COF can efficaciously produce superoxide radical anion (O2.−) after activating molecular oxygen (O2) which eventually drives aerobic photooxidative amidation reaction with high recyclability. This photocatalytic approach works well with a variety of substituted aromatic aldehydes having electron‐withdrawing or donating groups and cyclic, acyclic, primary or secondary amines with moderate to high yield. Furthermore, catalytic mechanism was established by monitoring the real‐time reaction progress through in situ diffuse reflectance infrared Fourier transform spectroscopic (DRIFTS) study.

Microwave Assisted Fast Synthesis of a Donor-Acceptor COF Towards Photooxidative Amidation Catalysis.

The synthesis of covalent organic frameworks (COFs) at bulk scale require robust, straightforward, and cost-effective techniques. However, the traditional solvothermal synthetic methods of COFs suffer low scalability as well as requirement of sensitive reaction environment and multiday reaction time (2-10 days) which greatly restricts their practical application. Here, we report microwave assisted rapid and optimized synthesis of a donor-acceptor (D-A) based highly crystalline COF, TzPm-COF in second (10 sec) to minute (10 min) time scale. With increasing the reaction time from seconds to minutes crystallinity, porosity and morphological changes are observed for TzPm-COF. Owing to visible range light absorption, suitable band alignment, and low exciton binding energy (Eb=64.6 meV), TzPm-COF can efficaciously produce superoxide radical anion (O2⋅-) after activating molecular oxygen (O2) which eventually drives aerobic photooxidative amidation reaction with high recyclability. This photocatalytic approach works well with a variety of substituted aromatic aldehydes having electron-withdrawing or donating groups and cyclic, acyclic, primary or secondary amines with moderate to high yield. Furthermore, catalytic mechanism was established by monitoring the real-time reaction progress through in situ diffuse reflectance infrared Fourier transform spectroscopic (DRIFTS) study.

Dion-Jacobson-Phase 2D Sn-Based Perovskite Comprising a High Dipole Moment of π-Conjugated Short-Chain Organic Spacers for High-Performance Solar Cell Applications.

The stability issue of Sn-based perovskite solar cells (PSCs) is expected to be resolved by involving a two-dimensional (2D) layered structure. However, Sn-based 2D PSCs, especially Dion-Jacobson (DJ)-phase ones with potentially good stability, have rarely been reported. Herein, superior DJ-phase Sn 2D perovskites with 3-aminobenzylamine (3ABA2+) or 4-aminobenzylamine (4ABA2+) π-conjugated short-chain ligands are reported to fabricate efficient 2D lead-free PSCs. Notably, the high dipole moment of the 3ABAI2 organic spacer is approved to possess faster charge transfer for forming (3ABA)FA4Sn5I16 2D perovskite with an extremely low exciton binding energy (only 84 meV). In combination with a diacetate partial substitution and methylamine iodide/bromide (MAI/MABr) post-treatment strategy to delay crystallization and improve compactness and coverage of the perovskite film, a record power conversion efficiency (PCE) of 6.81% and stability of 840 h (less than 5% degradation in a N2 atmosphere for unencapsulated devices) are acquired in eventual (3ABA)FA4Sn5I16 2D PSCs, which are among the highest PCE and the longest stability of Sn-based 2D PSCs reported to date. Our work provides a prospective molecule design and film preparation strategy of 2D Sn perovskites toward nontoxic high-performance tin-based PSCs, which pushes the almost stagnant research forward.

Pattern-Matched Polymer Ligands Toward Near-Perfect Synergistic Passivation for High-Performance and Stable Br/Cl Mixed Perovskite Light-Emitting Diodes.

Mixed Br/Cl perovskite nanocrystals (PeNCs) exhibit bright pure-blue emission benefiting for fulfilling the Rec. 2100 standard. However, phase segregation remains a significant challenge that severely affects the stability and emission spectrum of perovskite light-emitting diodes (PeLEDs). Here, we demonstrate the optimization of the spacing between polydentate functional groups of polymer ligands to match the surface pattern of CsPbBr1.8Cl1.2 PeNCs, resulting in effective synergistic passivation effect and significant improvements in PeLED performances. The block and alternating copolymers with different inter-functional group spacing are facilely synthesized as ligands for PeNCs. Surprisingly, block copolymers with a higher functional group density do not match PeNCs, while alternating copolymers enable efficient PeNCs with the high photoluminescence intensity, low non-radiative recombination rate and high exciton binding energy. Density functional theory calculations clearly confirm the almost perfect match between alternating copolymers and PeNCs. Finally, pure-blue PeLEDs are achieved with the emission at 467 nm and Commission Internationale de l'Eclairage (CIE) coordinates of (0.131, 0.071), high external quantum efficiency (9.1 %) and record spectral and operational stabilities (~80 mins) in mixed-halide PeLEDs. Overall, this study contributes to designing the polymer ligands and promoting the development of high-performance and stable pure-color PeLEDs towards display applications.