Advanced surface passivation for high-sensitivity studies of biomolecular condensates.

Biomolecular condensates are cellular compartments that concentrate biomolecules without an encapsulating membrane. In recent years, significant advances have been made in the understanding of condensates through biochemical reconstitution and microscopic detection of these structures. Quantitative visualization and biochemical assays of biomolecular condensates rely on surface passivation to minimize background and artifacts due to condensate adhesion. However, the challenge of undesired interactions between condensates and glass surfaces, which can alter material properties and impair observational accuracy, remains a critical hurdle. Here, we introduce an efficient, broadly applicable, and simple passivation method employing self-assembly of the surfactant Pluronic F127 (PF127). The method greatly reduces nonspecific binding across a range of condensates systems for both phase-separated droplets and biomolecules in dilute phase. Additionally, by integrating PF127 passivation with the Biotin-NeutrAvidin system, we achieve controlled multipoint attachment of condensates to surfaces. This not only preserves condensate properties but also facilitates long-time fluorescence recovery after photobleaching imaging and high-precision single-molecule analyses. Using this method, we have explored the dynamics of polySIM molecules within polySUMO/polySIM condensates at the single-molecule level. Our observations suggest a potential heterogeneity in the distribution of available polySIM-binding sites within the condensates.

Metal Fluorides Passivate II-VI and III-V Quantum Dots.

Quantum dots (QDs) with metal fluoride surface ligands were prepared via reaction with anhydrous oleylammonium fluoride. Carboxylate terminated II-VI QDs underwent carboxylate for fluoride exchange, while InP QDs underwent photochemical acidolysis yielding oleylamine, PH3, and InF3. The final photoluminescence quantum yield (PLQY) reached 83% for InP and near unity for core-shell QDs. Core-only CdS QDs showed dramatic improvements in PLQY, but only after exposure to air. Following etching, the InP QDs were bound by oleylamine ligands that were characterized by the frequency and breadth of the corresponding ν(N-H) bands in the infrared absorption spectrum. The fluoride content (1.6-9.2 nm-2) was measured by titration with chlorotrimethylsilane and compared with the oleylamine content (2.3-5.1 nm-2) supporting the formation of densely covered surfaces. The influence of metal fluoride adsorption on the air stability of QDs is discussed.

Precursor Engineering Induced High-Efficiency Electroluminescence of Quasi-Two-Dimensional Perovskites: A Synergistic Defect Inhibition and Passivation Approach.

Despite light-emitting diodes (LEDs) based on quasi-two-dimensional (Q-2D) perovskites being inexpensive and exhibiting high performance, defects still limit the improvement of electroluminescence efficiency and stability by causing nonradiative recombination. Here, an organic molecule, 1-(o-tolyl) biguanide, is used to simultaneously inhibit and passivate defects of Q-2D perovskites via in situ synchronous crystallization. This molecule not only prevents surface bromine vacancies from forming through hydrogen bonding with the bromine of intermediaries but also passivates surface defects through its interaction with uncoordinated Pb. Via combination of defect inhibition and passivation, the trap density of Q-2D perovskite films can be significantly reduced, and the emission efficiency of the film can be improved. Consequently, the corresponding LED shows an external quantum efficiency of 24.3%, and its operational stability has been increased nearly 15 times.

Lifting the Concentration Limit of Mass Photometry by PEG Nanopatterning.

Mass photometry (MP) is a rapidly growing optical technique for label-free mass measurement of single biomolecules in solution. The underlying measurement principle provides numerous advantages over ensemble-based methods but has been limited to low analyte concentrations due to the need to uniquely and accurately quantify the binding of individual molecules to the measurement surface, which results in diffraction-limited spots. Here, we combine nanoparticle lithography with surface PEGylation to substantially lower surface binding, resulting in a 2 orders of magnitude improvement in the upper concentration limit associated with mass photometry. We demonstrate the facile tunability of degree of passivation, enabling measurements at increased analyte concentrations. These advances provide access to protein-protein interactions in the high nanomolar to low micromolar range, substantially expanding the application space of mass photometry.

Magnetic State Control of Non-van der Waals 2D Materials by Hydrogenation.

Controlling the magnetic state of two-dimensional (2D) materials is crucial for spintronics. By employing data-mining and autonomous density functional theory calculations, we demonstrate the switching of magnetic properties of 2D non-van der Waals materials upon hydrogen passivation. The magnetic configurations are tuned to states with flipped and enhanced moments. For 2D CdTiO3─a diamagnetic compound in the pristine case─we observe an onset of ferromagnetism upon hydrogenation. Further investigation of the magnetization density of the pristine and passivated systems provides a detailed analysis of modified local spin symmetries and the emergence of ferromagnetism. Our results indicate that selective surface passivation is a powerful tool for tailoring magnetic properties of nanomaterials, such as non-vdW 2D compounds.

Reconstruction and Solidification of Dion-Jacobson Perovskite Top and Buried Interfaces for Efficient and Stable Solar Cells.

Quasi-two-dimensional (Q-2D) perovskites show great potential in the field of photonic and optoelectronic device applications. However, defects and local lattice dislocation still limit performance and stability improvement by nonradiative recombination, unpreferred phase distribution, and unbonded amines. Here, a low-temperature synergistic strategy for both reconstructing and solidifying the perovskite top and buried interface is developed. By post-treating the 1,4-phenylenedimethanammonium (PDMA) based (PDMA)MA4Pb5I16 films with cesium acetate (CsAc) before thermal annealing, a condensation reaction between R-COO- and -NH2 and ion exchange between Cs+ and MA+ occur. It converts the unbonded amines to amides and passivates uncoordinated Pb2+. Meanwhile, it adjusts film composition and improves the phase distribution without changing the out-of-plane grain orientation. Consequently, performance of 18.1% and much-enhanced stability (e.g., stability for photo-oxygen increased over 10 times, light-thermal for T90 over 4 times, and reverse bias over 3 times) of (PDMA)MA4Pb5I16 perovskite solar cells are demonstrated.

Surface Engineering Enables Efficient AgBiS2 Quantum Dot Solar Cells.

Surface ligand chemistry is vital to control the synthesis, diminish surface defects, and improve the electronic coupling of quantum dots (QDs) toward emerging applications in optoelectronic devices. Here, we successfully develop highly homogeneous and dispersed AgBiS2 QDs, focus on the control of interdot spacing, and substitute the long-chain ligands with ammonium iodide in solution. This results in improved electronic coupling of AgBiS2 QDs with excellent surface passivation, which greatly facilitates carrier transport within the QD films. Based on the stable AgBiS2 QD dispersion with the optimal ligand state, a homogeneous and densely packed QD film is prepared by a facile one-step coating process, delivering a champion power conversion efficiency of approximately 8% in the QD solar cells with outstanding shelf life stability. The proposed surface engineering strategy holds the potential to become a universal preprocessing step in the realm of high-performance QD optoelectronic devices.

GaN Surface Passivation by MoS2 Coating.

In this study, we investigate the impact of two-dimensional MoS2 coating on the optical properties of surface GaN/AlGaN quantum wells (QWs). A strong enhancement in GaN QW light emission is observed with monolayer-MoS2 coating, yielding luminescence intensity comparable to that from a QW capped by an AlGaN barrier. Our results demonstrate that MoS2, despite its quite different nature from III-nitride semiconductors, acts as an effective barrier for surface GaN QWs and suppresses spatially localized intrinsic surface states. This finding provides novel pathways for efficient III-nitride surface passivation.

Passivating Grain Boundaries via Graphene Additive for Efficient Kesterite Solar Cells.

Grain boundaries (GBs)-triggered severe non-radiative recombination is recently recognized as the main culprits for carrier loss in polycrystalline kesterite photovoltaic devices. Accordingly, further optimization of kesterite-based thin film solar cells critically depends on passivating the grain interfaces of polycrystalline Cu2 ZnSn(S,Se)4 (CZTSSe) thin films. Herein, 2D material of graphene is first chosen as a passivator to improve the detrimental GBs. By adding graphene dispersion to the CZTSSe precursor solution, single-layer graphene is successfully introduced into the GBs of CZTSSe absorber. Due to the high carrier mobility and electrical conductivity of graphene, GBs in the CZTSSe films are transforming into electrically benign and do not act as high recombination sites for carrier. Consequently, benefitting from the significant passivation effect of GBs, the use of 0.05 wt% graphene additives increases the efficiency of CZTSSe solar cells from 10.40% to 12.90%, one of the highest for this type of cells. These results demonstrate a new route to further increase kesterite-based solar cell efficiency by additive engineering.

Designing Surface Passivators Through Intramolecular Potential Manipulation for Efficient and Stable Perovskite Solar Cells.

The conjugation of terminal ammonium salt groups with perovskite surfaces is a frequently employed technique that aims to enhance the overall performance of perovskite materials, encompassing both bulk and surface properties. Particularly, it exhibits heightened efficacy when applied to surface modification, due to its ability to mitigate defect accumulation and facilitate facile binding with the receptive sites inherent to the perovskite structure. However, the interaction of the bulk ammonium group with PbI2 has the potential to form a low-dimensional phase of perovskite, which may obstruct carrier extraction at the interface. Therefore, the surface passivators (MeO-PFACl) are designed through intramolecular potential manipulation. The combinations of the electron-donating methoxy group and π-π conjugation of the phenyl ring reduce the local potential at the reactive site of formamidinium group, making it less likely to form a low-dimension phase with perovskite. This surface passivation strategy effectively suppresses the surface nonradiative recombination and promotes the interface carrier extraction. The devices treated with MeO-PFACl have demonstrated exceptional performance, achieving a peak power conversion efficiency (PCE) of 25.88%, with an average PCE of 25.37%. These works offer a novel principle for enhancing both the efficiency and stability of PSCs using ammonium-incorporated molecules without the induction of an additional phase layer.

Enhancing Performance and Stability of Perovskite Solar Cells with a Novel Formamidine Group Additive.

Perovskite materials, particularly FAPbI3, have emerged as promising candidates for solar energy conversion applications. However, these materials are plagued by well-known defects and suboptimal film quality. Enhancing crystallinity and minimizing defect density are therefore essential steps in the development of high-performance perovskite solar cells. In this study, 1H-Pyrazole-1-carboximidamide hydrochloride (PCH) is introduced into FAPbI3 perovskite films. The molecular structure of PCH features a pyrazole ring bonded to formamidine (FA). The FA moiety of PCH facilitated the incorporation of this additive into the film lattice, while the negatively charged pyrazole ring effectively passivated positively charged iodine vacancies. The presence of PCH led to the fabrication of an FAPbI3 device with improved crystallinity, a smoother surface, and reduced defect density, resulting in enhanced Voc and fill factor. A record power conversion efficiency of 24.62% is achieved, along with exceptional stability under prolonged air exposure and thermal stress. The findings highlight the efficacy of PCH as a novel additive for the development of high-performance perovskite solar cells.

Effective Small Organic Molecule as a Defect Passivator for Highly Efficient Quasi-2D Perovskite Light-Emitting Diodes.

The use of a small organic molecular passivator is proven to be a successful strategy for producing higher-performing quasi-2D perovskite light-emitting diodes (PeLEDs). The small organic molecule can passivate defects on the grain surround and surface of perovskite crystal structures, preventing nonradiative recombination and charge trapping. In this study, a new small organic additive called 2, 8-dibromodibenzofuran (diBDF) is reported and examines its effectiveness as a passivating agent in high-performance green quasi-2D PeLEDs. The oxygen atom in diBDF, acting as a Lewis base, forms coordination bonds with uncoordinated Pb2+, so enhancing the performance of the device. In addition, the inclusion of diBDF in the quasi-2D perovskite results in a decrease in the abundance of low-n phases, hence facilitating efficient carrier mobility. Consequently, PeLED devices with high efficiency are successfully produced, exhibiting an external quantum efficiency of 19.9% at the emission wavelength of 517 nm and a peak current efficiency of 65.0 cd A-1.

Multi-Functional Regulation on Buried Interface for Achieving Efficient Triple-Cation Perovskite Solar Cells.

Mixed-cation perovskite solar cells (PSCs) have attracted much attention because of the advantages of suitable bandgap and stability. It is still a challenge to rationally design and modify the perovskite/tin oxide (SnO2) heterogeneous interface for achieving highly efficient and stable PSCs. Herein, a strategy of one-stone-for-three-birds is proposed to achieve multi-functional interface regulation via introducing N-Chlorosuccinimide (NCS) into the solution of SnO2: i) C═O functional group in NCS can induces strong binding affinity to uncoordinated defects (oxygen vacancies, free lead ions, etc) at the buried interface and passivate them; ii) incomplete in situ hydrolysis reactions can occur spontaneously and adjust the pH value of the SnO2 solution to achieve a more matchable energy level; iii) effectively releasing the residual stress of the underlying perovskite. As a result, a champion power conversion efficiency (PCE) of 24.74% is achieved with a device structure of ITO/SnO2/Perovskite/Spiro-OMeTAD/Ag, which is one of the highest values for cesium-formamidinium-methylammonium (CsFAMA) triple cation PSCs. Furthermore, the device without encapsulation can sustain 94.6% of its initial PCE after the storage at room temperature and relative humidity (RH) of 20% for 40 days. The research provides a versatile way to manipulate buried interface for achieving efficient and stable PSCs.

Electrochemiluminescence Enhancement and Passivation Mitigation in Carbon Nitride Semiconductors via an Integrated Ternary Heterostructure Strategy.

In recent years, carbon nitride (CN) has attracted substantial attention in the field of electrochemiluminescence (ECL) applications, owing to its outstanding optical and electronic properties. However, the passivation of CN during the ECL process has contributed to reduced stability and poor repeatability. While some studies have tried to boost ECL performance by altering CN through doping and vacancies, effectively suppressing CN passivation at high potentials continues to be challenge. In this study, the built-in electric field and the Schottky barrier effect is used to expedite the transfer of electrons from CN to the molybdenum disulfide (MoS2) conduction band. This transfer deterred excessive electron injection into the CN band, thus mitigating its electrochemical degradation. Moreover, by introducing nickel nanoparticles (Ni NPs) as catalytic active sites, it is facilitated that the decomposition of potassium persulfate (K2S2O8), thereby enhancing both the stability and intensity of ECL emission. In the end, the application of ternary heterostructure as sensing platform for the cancer biomarker carcinoembryonic antigen (CEA) demonstrated high sensitivity. This research introduces a novel approach to overcome CN passivation, paving the way for more promising applications of CN in energy, environmental, and biosensing fields.

Ultrasmall 2D Sn-Doped MAPbBr3 Nanoplatelets Enable Bright Pure-Blue Emission.

Synthesis of perovskites that exhibit pure-blue emission with high photoluminescence quantum yield (PLQY) in both nanocrystal solutions and nanocrystal-only films presents a significant challenge. In this work, a room-temperature method is developed to synthesize ultrasmall, monodispersed, Sn-doped methylammonium lead bromide (MAPb1- xSnxBr3) perovskite nanoplatelets (NPLs) in which the strong quantum confinement effect endows pure blue emission (460 nm) and a high quantum yield (87%). Post-treatment using n-hexylammonium bromide (HABr) repaired surface defects and thus substantially increased the stability and PLQY (80%) of the NPL films. Concurrently, high-precision patterned films (200-µm linewidth) are successfully fabricated by using cost-effective spray-coating technology. This research provides a novel perspective for the preparation of high PLQY, highly stable, and easily processable perovskite nanomaterials.

An Eco-Friendly Passivation Strategy of Resveratrol for Highly Efficient and Antioxidative Perovskite Solar Cells.

The stability of perovskite solar cells is closely related to the defects in perovskite crystals, and a large number of crystal defects are caused by the solution method. In this study, resveratrol (RES), a green natural antioxidant abundant in knotweed and grape leaves, is introduced into perovskite films to passivate the defect. RES achieves defect passivation by interacting with uncoordinated Pb2+ in perovskite films. The defect formation energy of VPb and PbI on the surface of perovskite thin films is increased by RES doping, as calculated by density functional theory. The results show that the quality of the perovskite film is significantly improved, and the energy level structure of the device is optimized, and the power conversion efficiency (PCE) of the device is increased from 21.62% to 23.44%. RES can hinder the degradation of perovskite structures by O2 - free radicals, and the device retained 88% of its initial PCE after over 1000 h in pure oxygen environment. The device retains 91% of the initial PCE after >1000 h at 25 °C and 50 ± 5% relative humidity. This work provides an idea for the use of natural and environmentally friendly additives to improve the efficiency and stability of devices.

Synergy Between Dynamic Behavior of Hydrogen Defects and Non-Radiative Recombination in Metal-Halide Perovskites.

In organic-inorganic hybrid perovskite solar cells (PSCs), hydrogen defects introduce deep-level trap states, significantly influencing non-radiative recombination processes. Those defects are primarily observed in MA-PSCs rather than FA-PSCs. As a result, MA-PSCs demonstrated a lower efficiency of 23.6% compared to 26.1% of FA-PSCs. In this work, both hydrogen vacancy (VH -) and hydrogen interstitial (Hi -) defects in MAPbI3 bulk and on surfaces, respectively are investigated. i) Bulk VH - defects have dramatic impact on non-radiative recombination, with lifetime varying from 67 to 8 ns, depending on whether deprotonated MA0 are ion-bonded or not. ii) Surface H-defects exhibited an inherent self-healing mechanism through a chemical bond between MA0 and Pb2+, indicating a self-passivation effect. iii) Both VH - and Hi - defects can be mitigated by alkali cation passivation; while large cations are preferable for VH - passivation, given strong binding energy of cation/perovskite, as well as, weak band edge non-adiabatic couplings; and small cations are suited for Hi - passivation, considering the steric hindrance effect. The dual passivation strategy addressed diverse experimental outcomes, particularly in enhancing performance associated with cation selections. The dynamic connection between hydrogen defects and non-radiative recombination is elucidated, providing insights into hydrogen defect passivation essential for high-performance PSCs fabrication.

Competitive Formation Mechanism for Bidentate Passivation of Halogen Vacancies in Perovskite Based on 6-Chloropurine.

For metal halide perovskite solar cells, bidentate passivation (BP) is highly effective, but currently, only passivation sites rather than molecular environments are being considered. Here, the authors report an effective approach for high-performance fully printable mesoscopic perovskite solar cells (FP-PSCs) through the BP strategy using the multidentate molecule 6-chloropurine (6-CP). By utilizing density functional theory (DFT) calculations, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) characterizations, the competition mechanism is identified of BP between the chlorine atom and neighboring nitrogen atom of the imidazole and pyrimidine rings. Through BP between the chlorine atom and adjacent nitrogen atom in imidazole, the power conversion efficiency (PCE) of the pristine samples is significantly enhanced from 16.25% to 17.63% with 6-CP. The formation of BP enhances interfacial hole selectivity and charge transfer, and suppresses nonradiative recombination, improving device stability under high humidity conditions. The competition mechanism of BP between two aromatic cycles provides a path for designing molecular passivants and selecting passivation pathways to approach theoretical limits.

Multifunctional Effects of Biguanide Derivative in the Application of Highly Efficient Tin-Lead Perovskite Solar Cells.

Tin-lead (Sn-Pb) mixed perovskites is beneficial to a single-junction or all-perovskite tandem device. However, the poor quality of the perovskite surface resulting from Sn2+ oxidation and uncontrollable crystallization degrades device performance and stability. Herein, based on interface engineering, a novel biguanide derivative of PZBGACl is employed that integrates different types of N-related groups to reconstruct the surface/grain boundaries of Sn-Pb perovskite. Combined with the microcorrosion effect of isopropanol solvent, PZBGACl can induce surface recrystallization of perovskite, and passivate various types of defects via hydrogen bond or Lewis acid-base interaction, leading to an excellent perovskite film with reduced stress, larger grain size, and more n-type surface. As a result, the obtained Sn-Pb solar cell achieves a power conversion efficiency of 22.0%, and exhibits excellent N2 storage/operation stability.

Comprehensive Crystal Regulation Reduces Interfacial Energy Loss for Efficient Blue Perovskite Light-Emitting Diodes.

As an essential component of future full-color displays, blue perovskite light-emitting diodes (PeLEDs) still lag far behind the red and green counterparts in the device performances. In the mainstream quasi-2D blue perovskite system, trap-mediated nonradiative loss, low energy transfer efficiency, and interface fluorescence quenching remain significant challenges. Herein, guanidinium thiocyanate (GASCN) and potassium cinnamate (PCA) are respectively introduced into the hole transport layer (HTL) and the perovskite precursor to achieve a dense and uniform perovskite thin film with greatly improved optoelectronic properties. Therefore, adequate GA+ acts as pre-nucleation sites on the HTL surface, regulating crystallization through strong hydrogen bonding with perovskite intermediates. The realized polydisperse domain distribution is conducive to cascade energy transfer, and the improved hole transport ability alleviates interface fluorescence quenching. In addition, the SCN- and CA- groups can form coordination bonds with the defects at the buried perovskite interface and grain boundaries, respectively, which effectively suppresses the detrimental nonradiative recombination. Benefitting from the comprehensive crystal regulation, blue PeLEDs featuring stable emission at 484 and 468 nm exhibit improved external quantum efficiencies of 11.5% and 4.3%, respectively.