Materials Futures

Perovskite solar cells have aroused a worldwide research upsurge in recent years due to their soaring photovoltaic performance, ease of solution processing, and low cost. The power conversion efficiency record is constantly being broken and has recently reached 26.1% in the lab, which is comparable to the established photovoltaic technologies such as crystalline silicon, copper indium gallium selenide and cadmium telluride (CdTe) solar cells. Currently, perovskite solar cells are standing at the entrance of industrialization, where huge opportunities and risks coexist. However, towards commercialization, challenges of up-scaling, stability and lead toxicity still remain, the proper handling of which could potentially lead to the widespread adoption of perovskite solar cells as a low-cost and efficient source of renewable energy. This review gives a holistic analysis of the path towards commercialization for perovskite solar cells. A comprehensive overview of the current state-of-the-art level for perovskite solar cells and modules will be introduced first, with respect to the module efficiency, stability and current status of industrialization. We will then discuss the challenges that get in the way of commercialization and the corresponding strategies to address them, involving the upscaling, the stability and the lead toxicity issue. Insights into the future direction of commercialization of perovskite photovoltaics was also provided, including the flexible perovskite cells and modules and perovskite indoor photovoltaics. Finally, the future perspectives towards commercialization are put forward.

Charge-transporting layers (CTLs) are important in determining the performance and stability of perovskite solar cells (PSCs). Recently, there has been considerable use of self-assembled monolayers (SAMs) as charge-selective contacts, especially for hole-selective SAMs in inverted PSCs as well as perovskite involving tandem solar cells. The SAM-based charge-selective contact shows many advantages over traditional thin-film organic/inorganic CTLs, including reduced cost, low optical and electric loss, conformal coating on a rough substrate, simple deposition on a large-area substrate and easy modulation of energy levels, molecular dipoles and surface properties. The incorporation of various hole-selective SAMs has resulted in high-efficiency single junction and tandem solar cells. This topical review summarizes both the advantages and challenges of SAM-based charge-selective contacts, and discusses the potential direction for future studies.

While all-solid-state batteries have built global consensus with regard to their impact in safety and energy density, their anode-less versions have attracted appreciable attention because of the possibility of further lowering the cell volume and cost. This perspective article summarizes recent research trends in anode-less all-solid-state batteries (ALASSBs) based on different types of solid electrolytes and anticipates future directions these batteries may take. We particularly aim to motivate researchers in the field to challenge remaining issues in ALASSBs by employing advanced materials and cell designs.

P2-type layered oxides with the general Na-deficient composition Na_xTMO₂ (x < 1, TM: transition metal) are a promising class of cathode materials for sodium-ion batteries. The open Na⁺ transport pathways present in the structure lead to low diffusion barriers and enable high charge/discharge rates. However, a phase transition from P2 to O2 structure occurring above 4.2 V and metal dissolution at low potentials upon discharge results in rapid capacity degradation. In this work, we demonstrate the positive effect of configurational entropy on the stability of the crystal structure during battery operation. Three different compositions of layered P2-type oxides were synthesized by solid-state chemistry, Na_0.67(Mn_0.55Ni_0.21Co_0.24)O₂, Na_0.67(Mn_0.45Ni_0.18Co_0.24Ti_0.1Mg_0.03)O₂ and Na_0.67(Mn_0.45Ni_0.18Co_0.18Ti_0.1Mg_0.03Al_0.04Fe_0.02)O₂ with low, medium and high configurational entropy, respectively. The high-entropy cathode material shows lower structural transformation and Mn dissolution upon cycling in a wide voltage range from 1.5 to 4.6 V. Advanced operando techniques and post-mortem analysis were used to probe the underlying reaction mechanism thoroughly. Overall, the high-entropy strategy is a promising route for improving the electrochemical performance of P2 layered oxide cathodes for advanced sodium-ion battery applications.

To fill the gap between accurate (and expensive) ab initio calculations and efficient atomistic simulations based on empirical interatomic potentials, a new class of descriptions of atomic interactions has emerged and been widely applied; i.e. machine learning potentials (MLPs). One recently developed type of MLP is the deep potential (DP) method. In this review, we provide an introduction to DP methods in computational materials science. The theory underlying the DP method is presented along with a step-by-step introduction to their development and use. We also review materials applications of DPs in a wide range of materials systems. The DP Library provides a platform for the development of DPs and a database of extant DPs. We discuss the accuracy and efficiency of DPs compared with ab initio methods and empirical potentials.

Magnetic skyrmions are vortex-like spin configurations that possess nanometric dimensions, topological stability, and high controllability through various external stimuli. Since their first experimental observation in helimagnet MnSi in 2009, magnetic skyrmions have emerged as a highly promising candidate for carrying information in future high-performance, low-energy-consumption, non-volatile information storage, and logical calculation. In this article, we provide a comprehensive review of the progress made in the field of magnetic skyrmions, specifically in materials, manipulation, detection, and application in spintronic devices. Firstly, we introduce several representative skyrmion material systems, including chiral magnets, magnetic thin films, centrosymmetric materials, and Van der Waals materials. We then discuss various methods for manipulating magnetic skyrmions, such as electric current and electric field, as well as detecting them, mainly through electrical means such as the magnetoresistance effect. Furthermore, we explore device applications based on magnetic skyrmions, such as track memory, logic computing, and neuromorphic devices. Finally, we summarize the challenges faced in skyrmion research and provide future perspectives.

The performance of red InP and blue ZnTeSe-based quantum dots (QDs) and corresponding QD light emitting diodes (QLEDs) has already been improved significantly, whose external quantum efficiencies (EQEs) and luminances have exceeded 20% and 80 000 cd m⁻², respectively. However, the inferior performance of the green InP-based device hinders the commercialization of full-color Cd-free QLED technology. The ease of oxidation of the highly reactive InP cores leads to high non-radiative recombination and poor photoluminescence quantum yield (PL QY) of the InP-based core/shell QDs, limiting the performance of the relevant QLEDs. Here, we proposed a fluoride-free synthesis strategy to in-situ passivate the InP cores, in which zinc myristate reacted with phosphine dangling bonds to form Zn–P protective layer and protect InP cores from the water and oxygen in the environment. The resultant InP/ZnSe/ZnS core/shell QDs demonstrated a high PL QY of 91%. The corresponding green-emitting electroluminescence devices exhibited a maximum EQE of 12.74%, along with a luminance of over 175 000 cd m⁻² and a long T₅₀@100 cd m⁻² lifetime of over 20 000 h.

Organic electronics have gained significant attention in the field of biosensors owing to their immense potential for economical, lightweight, and adaptable sensing devices. This review explores the potential of organic electronics-based biosensors as a revolutionary technology for biosensing applications. The focus is on two types of organic biosensors: organic field effect transistor (OFET) and organic electrochemical transistor (OECT) biosensors. OFET biosensors have found extensive application in glucose, DNA, enzyme, ion, and gas sensing applications, but suffer from limitations related to low sensitivity and selectivity. On the other hand, OECT biosensors have shown superior performance in sensitivity, selectivity, and signal-to-noise ratio, owing to their unique mechanism of operation, which involves the modulation of electrolyte concentration to regulate the conductivity of the active layer. Recent advancements in OECT biosensors have demonstrated their potential for biomedical and environmental sensing, including the detection of neurotransmitters, bacteria, and heavy metals. Overall, the future directions of OFET and OECT biosensors involve overcoming these challenges and developing advanced devices with improved sensitivity, selectivity, reproducibility, and stability. The potential applications span diverse fields including human health, food analysis, and environment monitoring. Continued research and development in organic biosensors hold great promise for significant advancements in sensing technology, opening up new possibilities for biomedical and environmental applications.

The production of hydrogen through water electrolysis (WE) from renewable electricity is set to revolutionise the energy sector that is at present heavily dependent on fossil fuels. However, there is still a pressing need to develop advanced electrocatalysts able to show high activity and withstand industrially-relevant operating conditions for a prolonged period of time. In this regard, high entropy materials (HEMs), including high entropy alloys and high entropy oxides, comprising five or more homogeneously distributed metal components, have emerged as a new class of electrocatalysts owing to their unique properties such as low atomic diffusion, structural stability, a wide variety of adsorption energies and multi-component synergy, making them promising catalysts for challenging electrochemical reactions, including those involved in WE. This review begins with a brief overview about WE technologies and a short introduction to HEMs including their synthesis and general physicochemical properties, followed by a nearly exhaustive summary of HEMs catalysts reported so far for the hydrogen evolution reaction, the oxygen evolution reaction and the overall water splitting in both alkaline and acidic conditions. The review concludes with a brief summary and an outlook about the future development of HEM-based catalysts and further research to be done to understand the catalytic mechanism and eventually deploy HEMs in practical water electrolysers.

Fragility is one of the central concepts in glass and liquid sciences, as it characterizes the extent of deviation of viscosity from Arrhenius behavior and is linked to a range of glass properties. However, the intervention of crystallization often prevents the assessment of fragility in poor glass-formers, such as supercooled metallic liquids. Hence experimental data on their compositional dependence are scarce, let alone fundamentally understood. In this work, we use fast scanning calorimetry to overcome this obstacle and systematically study the fragility in a ternary La–Ni–Al system, over previously inaccessible composition space. We observe fragility dropped in a small range with the Al alloying, indicating an alloying-induced fragility crossover. We use x-ray photoelectron spectroscopy, resistance measurements, electronic structure calculations, and DFT-based deep-learning atomic simulations to investigate the cause of this fragility drop. These results show that the fragility crossover can be fundamentally ascribed to the electronic covalency associated with the unique Al–Al interactions. Our findings provide insight into the origin of fragility in metallic liquids from an electronic structure perspective and pave a new way for the design of metallic glasses.

The performance of red InP and blue ZnTeSe-based quantum dots (QDs) and corresponding QD light emitting diodes (QLEDs) has already been improved significantly, whose external quantum efficiencies (EQEs) and luminances have exceeded 20% and 80 000 cd m⁻², respectively. However, the inferior performance of the green InP-based device hinders the commercialization of full-color Cd-free QLED technology. The ease of oxidation of the highly reactive InP cores leads to high non-radiative recombination and poor photoluminescence quantum yield (PL QY) of the InP-based core/shell QDs, limiting the performance of the relevant QLEDs. Here, we proposed a fluoride-free synthesis strategy to in-situ passivate the InP cores, in which zinc myristate reacted with phosphine dangling bonds to form Zn–P protective layer and protect InP cores from the water and oxygen in the environment. The resultant InP/ZnSe/ZnS core/shell QDs demonstrated a high PL QY of 91%. The corresponding green-emitting electroluminescence devices exhibited a maximum EQE of 12.74%, along with a luminance of over 175 000 cd m⁻² and a long T₅₀@100 cd m⁻² lifetime of over 20 000 h.

Perovskite solar cells have aroused a worldwide research upsurge in recent years due to their soaring photovoltaic performance, ease of solution processing, and low cost. The power conversion efficiency record is constantly being broken and has recently reached 26.1% in the lab, which is comparable to the established photovoltaic technologies such as crystalline silicon, copper indium gallium selenide and cadmium telluride (CdTe) solar cells. Currently, perovskite solar cells are standing at the entrance of industrialization, where huge opportunities and risks coexist. However, towards commercialization, challenges of up-scaling, stability and lead toxicity still remain, the proper handling of which could potentially lead to the widespread adoption of perovskite solar cells as a low-cost and efficient source of renewable energy. This review gives a holistic analysis of the path towards commercialization for perovskite solar cells. A comprehensive overview of the current state-of-the-art level for perovskite solar cells and modules will be introduced first, with respect to the module efficiency, stability and current status of industrialization. We will then discuss the challenges that get in the way of commercialization and the corresponding strategies to address them, involving the upscaling, the stability and the lead toxicity issue. Insights into the future direction of commercialization of perovskite photovoltaics was also provided, including the flexible perovskite cells and modules and perovskite indoor photovoltaics. Finally, the future perspectives towards commercialization are put forward.

Human skin perceives external environmental stimulus by the synergies between the subcutaneous tactile corpuscles. Soft electronics with multiple sensing capabilities by mimicking the function of human skin are of significance in health monitoring and artificial sensation. The last decade has witnessed unprecedented development and convergence between multimodal tactile sensing devices and soft bioelectronics. Despite these advances, traditional flexible electronics achieve multimodal tactile sensing for pressure, strain, temperature, and humidity by integrating monomodal sensing devices together. This strategy results in high energy consumption, limited integration, and complex manufacturing process. Various multimodal sensors and crosstalk-free sensing mechanisms have been proposed to bridge the gap between natural sensory system and artificial perceptual system. In this review, we provide a comprehensive summary of tactile sensing mechanism, integration design principles, signal-decoupling strategies, and current applications for multimodal tactile perception. Finally, we highlight the current challenges and present the future perspectives to promote the development of multimodal tactile perception.

Wearable electronics are advancing towards miniaturization and flexibility. However, traditional energy supply methods have largely hindered their development. An effective solution to this problem is to convert human mechanical energy into electricity to power wearable electronic devices. Therefore, it is greatly attractive to design flexible, foldable and even stretchable energy harvesting devices. Herein, we use the electrospinning and kirigami approach to develop a type of highly stretchable kirigami-patterned nanofiber-based triboelectric nanogenerator (K-TENG). Due to its innovative structural design, the K-TENG can achieve a tensile strain of 220%, independent of the tensile properties of the material itself. When a person swings their arms, the K-TENG fixed to the clothing can convert mechanical energy from human movement into electrical energy. The produced electricity can directly drive 50 LED lights and a digital watch, or be stored in a lithium battery to charge the smartwatch and smartphone, respectively. This study employs a new method to fabricate a stretchable triboelectric nanogenerator and demonstrates its promising applications in wearable power technology.

Perovskite solar cells have aroused a worldwide research upsurge in recent years due to their soaring photovoltaic performance, ease of solution processing, and low cost. The power conversion efficiency record is constantly being broken and has recently reached 26.1% in the lab, which is comparable to the established photovoltaic technologies such as crystalline silicon, copper indium gallium selenide and cadmium telluride (CdTe) solar cells. Currently, perovskite solar cells are standing at the entrance of industrialization, where huge opportunities and risks coexist. However, towards commercialization, challenges of up-scaling, stability and lead toxicity still remain, the proper handling of which could potentially lead to the widespread adoption of perovskite solar cells as a low-cost and efficient source of renewable energy. This review gives a holistic analysis of the path towards commercialization for perovskite solar cells. A comprehensive overview of the current state-of-the-art level for perovskite solar cells and modules will be introduced first, with respect to the module efficiency, stability and current status of industrialization. We will then discuss the challenges that get in the way of commercialization and the corresponding strategies to address them, involving the upscaling, the stability and the lead toxicity issue. Insights into the future direction of commercialization of perovskite photovoltaics was also provided, including the flexible perovskite cells and modules and perovskite indoor photovoltaics. Finally, the future perspectives towards commercialization are put forward.

Human skin perceives external environmental stimulus by the synergies between the subcutaneous tactile corpuscles. Soft electronics with multiple sensing capabilities by mimicking the function of human skin are of significance in health monitoring and artificial sensation. The last decade has witnessed unprecedented development and convergence between multimodal tactile sensing devices and soft bioelectronics. Despite these advances, traditional flexible electronics achieve multimodal tactile sensing for pressure, strain, temperature, and humidity by integrating monomodal sensing devices together. This strategy results in high energy consumption, limited integration, and complex manufacturing process. Various multimodal sensors and crosstalk-free sensing mechanisms have been proposed to bridge the gap between natural sensory system and artificial perceptual system. In this review, we provide a comprehensive summary of tactile sensing mechanism, integration design principles, signal-decoupling strategies, and current applications for multimodal tactile perception. Finally, we highlight the current challenges and present the future perspectives to promote the development of multimodal tactile perception.

Zero-dimensional graphene quantum dots (GQDs) exhibit many different properties, such as strong fluorescence, nonzero bandgap and solubility in solvents, compared to two-dimensional graphene. GQDs are biocompatible and have low toxicity; hence, they are widely used in the biomedical field. The edge effect of GQDs is of particular interest because edge modification can regulate the performance of nanomaterials. In this review, various preparation methods for GQDs, which can be divided into three main categories, namely top-down, bottom-up and chemical methods, are discussed. The unique optical, electrical, thermal and magnetic properties of GQDs are reviewed. The functionalization of GQDs by doping with heteroatoms and forming composites with other materials is studied, and the characteristics of these GQDs are also discussed. The applications of these GQDs in the fields of optics, electricity, optoelectronics, biomedicine, energy, agriculture and other emerging interdisciplinary fields are reviewed to highlight the enormous potential of nanomaterials. This review reports on the recent advancement in GQD research and suggests future directions for the development of GQDs.

In recent years, zinc-ion batteries (ZIBs) have been considered one of the most promising candidates for next-generation electrochemical energy storage systems due to their advantages of high safety, high specific capacity and high economic efficiency. As an indispensable component, the electrolyte has the function of connecting the cathode and the anode, and plays a key role in the performance of the battery. Different types of electrolytes have different effects on the performance of ZIBs, and the use of additives has further developed the research on modified electrolytes, thus effectively solving many serious problems faced by ZIBs. Therefore, to further explore the improvement of ZIBs by electrolyte engineering, it is necessary to summarize the current status of the design of various electrolyte additives, as well as their functions and mechanism in ZIBs. This paper analyzes the challenges faced by different electrolytes, reviews the different solutions of additives to solve battery problems in liquid electrolytes and solid electrolytes, and finally makes suggestions for the development of modified ZIB electrolytes. It is hoped that the review and strategies proposed in this paper will facilitate development of new electrolyte additives for ZIBs.

Detecting light from a wealth of physical degrees of freedom (e.g. wavelength, intensity, polarization state, phase, etc) enables the acquirement of more comprehensive information. In the past two decades, low-dimensional van der Waals materials (vdWMs) have established themselves as transformative building blocks toward lensless polarization optoelectronics, which is highly beneficial for optoelectronic system miniaturization. This review provides a comprehensive overview on the recent development of low-dimensional vdWM polarized photodetectors. To begin with, the exploitation of pristine 1D/2D vdWMs with immanent in-plane anisotropy and related heterostructures for filterless polarization-sensitive photodetectors is introduced. Then, we have systematically epitomized the various strategies to induce polarization photosensitivity and enhance the degree of anisotropy for low-dimensional vdWM photodetectors, including quantum tailoring, construction of core–shell structures, rolling engineering, ferroelectric regulation, strain engineering, etc, with emphasis on the fundamental physical principles. Following that, the ingenious optoelectronic applications based on the low-dimensional vdWM polarized photodetectors, including multiplexing optical communications and enhanced-contrast imaging, have been presented. In the end, the current challenges along with the future prospects of this burgeoning research field have been underscored. On the whole, the review depicts a fascinating landscape for the next-generation high-integration multifunctional optoelectronic systems.