Amplified narrowband perovskite photodetectors enabled by independent multiplication layers for anti-interference light detection

Metal-halide perovskite narrowband photodetectors offer a low-cost opportunity to detect specific signals covering a broad spectrum directly. However, the thickness of charge collection narrowing mechanism photodetectors increases recombination, resulting in performance bottlenecks. Here, we demonstrate amplified narrowband photodetectors that combine perovskite single-crystal absorbers and organic multiplication layers. The separation of the multiplication layer controls the density of trap states while amplifying the response of conventional narrowband photodetectors by more than 215 times. The carrier dynamics were characterized by ultrafast measurement, thus verifying the mechanism of response amplification. By analyzing multiplication with different trap states energy levels under charge injection, it is shown that dopants have a wide selection space, providing a feasible path for high-performance narrowband photodetectors. As a result, the external quantum efficiency of 2259% with a 38-nanometer full width at half maximum and the specific detectivity of 4.84 × 1012 Jones was obtained at 825 nanometers. Last, we demonstrated the anti-interference signal acquisition capability of our photodetector.

Heterovalent-Doped Sb2S3 Glass for Large-Area Sensitive X-ray Detection and Imaging

Flat-panel X-ray detectors are indispensable in a variety of imaging applications ranging from medical radiography to industrial inspections. Current commercial detectors (α-Se/CdTe) suffer from unsatisfactory image contrast and high-dose X-ray exposure owing to the limited attenuation and charge collection. Here, we show that heterovalent-doped Sb2S3 glass (α-Sb2S3) can effectively convert X-ray photons to electrical current signals. SnI2 doping modifies the Sb-S network and stabilizes the noncrystalline structure, enabling bulk α-Sb2S3 with a narrow bandgap (1.66 eV), large mobility-lifetime product (5.6 × 10-5 cm2 V-1), and strong radiation attenuation capacity simultaneously. The α-Sb2S3-based detector exhibits a high sensitivity of 4397 μC Gy1- cm-2, a low detection limit of 66 nGy s-1, and excellent stability. Thermally evaporated α-Sb2S3 on a pixelated thin film transistor (TFT) backplane enables high-resolution X-ray imaging. This is the first demonstration of Sb2S3-based X-ray detection and imaging, creating new possibilities for the development of amorphous semiconducting materials and devices.

Broadband photodetection of intense lasers via exciton-enhanced high-order multiphoton-absorption optoelectronics in 2D hybrid perovskite

Broadband photodetection, especially for the high-intensity pulsed lasers, has garnered increasing interest in photophysics and applied sciences driven by the development of pulsed lasers. However, direct broadband photodetection of high-intensity pulsed lasers, with precisely capturing their spatiotemporal properties, has been hampered by low saturation intensity or damage threshold of traditional optoelectronic materials. Here, we demonstrate that strategic enhancement of excitonic effects in two-dimensional (2D) layered hybrid perovskite can enable robust high-order multiphoton absorption (MPA) optoelectronics with achieving strong four-photon absorption (4PA) and five-photon absorption (5PA) nonlinearities as well as efficient electronic properties simultaneously. This effectively overcomes the limitations of mainstream photodetectors. Our approach facilitates direct photodetection and high-precision imaging of high-intensity femtosecond lasers (21.5 GW/cm2) across a broad wavelength range of 800 to 2300 nanometer. These results offer valuable insights into advancing high-order nonlinearity-based optoelectronics and provide practical solutions for direct measurement tools of intensive lasers, filling the blank of high-precision characterization of intense-field laser phenomena.

The impact of tris(pentafluorophenyl)borane hole transport layer doping on interfacial charge extraction and recombination

Selective charge transport layers have a strong influence on the overall efficiency and stability in perovskite solar cell devices. Specifically, the charge extraction and recombination occurring at the interfaces between the perovskite and these materials can be a limiting factor for performance. A lot of effort has been put into improving the conductivity of selective contacts, as well as the junction quality and energetic alignment with the absorber. On the hole extracting side, organic semiconductors have been extensively used due to their flexibility and favorable properties. Two of such compatible materials that have yielded high performing devices are the small molecule 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-OMeTAD) and the polymer poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA). In this work, we investigate the impact of hole transport layer doping on the performance and potential distribution in solar cells based on these materials. To do so on operating solar cells, we created samples with exposed cross-sections and examined their potential profile distributions with Kelvin probe force microscopy (KPFM), implementing our comprehensive measurement protocol. Using the Lewis acid tris(pentafluorophenyl)borane (BCF), we enhanced the hole extracting material/perovskite junction quality in spiro-OMeTAD and in PTAA based devices. Measurements under illumination show that the improvement is caused by a reduced recombination rate at the perovskite/hole transporter interface.

Perovskite Solar Cells and Light Emitting Diodes: Materials Chemistry, Device Physics and Relationship

Solution-processed perovskite solar cells (PSCs) and perovskite light emitting diodes (PeLEDs) represent promising next-generation optoelectronic technologies. This Review summarizes recent advancements in the application of metal halide perovskite materials for PSC and PeLED devices to address the efficiency, stability and scalability issues. Emphasis is placed on material chemistry strategies used to control and engineer the composition, deposition process, interface and micro-nanostructure in solution-processed perovskite films, leading to high-quality crystalline thin films for optimal device performance. Furthermore, we retrospectively compare the device physics of PSCs and PeLEDs, their working principles and their energy loss mechanisms, examining the similarities and differences between the two types of devices. The reciprocity relationship suggests that a great PSC should also be a great PeLED, motivating the search for interconverting photoelectric bifunctional devices with maximum radiative recombination and negligible non-radiative recombination. Specific requirements of PSCs and PeLEDs in terms of bandgap, thickness, band alignment and charge transport to achieve this target are discussed in detail. Further challenges and issues are also illustrated, together with prospects for future development. Understanding these fundamentals, embracing recent breakthroughs and exploring future prospects pave the way toward the rational design and development of high-performance PSC and PeLED devices.

The model of sub-bandgap light induced all-optical luminescence switching of lead-halide perovskite microcrystals

The phenomenon of sub-bandgap light induced luminescence switching for lead tribromide perovskite microcrystals with excess lead was recently discovered by Wan et al., Adv. Mater. 35, 2209851 (2023). It was found that the photoluminescence caused by the high energy excitation light is suppressed by the control light, the photon energy of which is less than the bandgap of the crystal, and is restored after switching off the control light. We propose an original model of this phenomenon, taking into account the spatially distributed kinetics of charge carrier recombination and the creation/annihilation of trap states induced by both light sources. The model successfully reproduces the main features of light induced luminescence switching.

Enhanced Interfacial Exciton Transport in Mixed 2D/3D Perovskites Approaching Bulk 3D Counterparts

Mixed 2D/3D halide perovskites possess unique optoelectronic properties and strong structural stability, making them promising for various light-harvesting and -emitting applications. However, the long-chain organic cations have low charge conductivity and create potential barriers within the inorganic frameworks, which limit efficient exciton and carrier transport. In this study, we propose a method to improve exciton transport in 2D/3D perovskites by adjusting the conjugation interactions of long-chain ligands. Through time-resolved spectroscopy and high-resolution transmission electron microscopy, we establish the relationship between the microstructure of 2D/3D perovskites and exciton mobility. We successfully create a 2D/3D halide perovskite film with an exciton transport value of 92 cm2 V-1 s-1, approaching its 3D bulk counterparts. We explain that the strong interligand conjugation of the naphthylmethylammonium cation aids in forming a 2D phase with a small value, which compresses the 2D domains to the nanometer scale, thereby enhancing carrier tunneling and exciton mobility across the 3D grain boundaries. These findings offer helpful perspectives for the development of high-mobility mixed 2D/3D perovskite films for applications in solar cells, light-emitting diodes, and photodetectors.

Nanoscopic Parylene Layer: Enhancing Perovskite Solar Cells Through Parylene-D Passivation

The development of eco-friendly energy sources has advanced photovoltaic technologies, with perovskite solar cells (PSCs) emerging as promising alternatives owing to their high efficiency, low fabrication costs, and excellent optical and electronic properties. However, their commercialization is hindered by stability issues, such as ion migration, defect-induced degradation, and nonuniformity of the solution process over large areas, particularly at the perovskite/hole-transporting layer (HTL) interface. To address these challenges, chemical vapor deposition (CVD) is employed to introduce an ultrathin, uniform parylene-D layer at the perovskite/HTL interface. Parylene-D, containing additional chlorine functional groups compared to parylene-C, supports bidentate chelation, enabling effective interaction with uncoordinated Pb2⁺ and perovskite surface defects. This passivation layer significantly reduces nonradiative recombination and suppresses ion migration without affecting the morphology or electrical properties of large-area perovskites. The optimized parylene-D treatment yields PSCs with 23.75% efficiency and enhanced open-circuit voltage and fill factor. Stability tests demonstrate that the parylene-D-treated devices retain their initial efficiency after 1500 h under 10% relative humidity at room temperature and maintain 80% efficiency after 1200 h at 65 °C in a nitrogen environment. Furthermore, the scalability of this approach is validated by fabricating a large-area module (25 cm2 aperture area), achieving module and active area efficiencies of 19.44% and 20.59%, respectively. These results highlight the potential of parylene-D passivation via CVD as a practical and scalable strategy to enhance PSC performance and stability.

Modification at ITO/NiOx Interface with MoS2 Enables Hole Transport for Efficient and Stable Inverted Perovskite Solar Cells

Inverted perovskite solar cells (IPSCs) utilizing nickel oxide (NiOx) as hole transport material have made great progress, driven by improvements in materials and interface engineering. However, challenges remain due to the low intrinsic conductivity of NiOx and inefficient hole transport. In this study, we introduced MoS2 nanoparticles at the indium tin oxide (ITO) /NiOx interface to enhance the ITO surface and optimize the deposition of NiOx, resulting in increased conductivity linked to a ratio of Ni3+:Ni2+. This interface modification not only optimized energy level but also promoted hole transport and reduced defects. Consequently, IPSCs with MoS2 modified at ITO/NiOx interface achieved a champion power conversion efficiency (PCE) of 21.42 %, compared to 20.25 % without modification. Additionally, unencapsulated IPSCs with this interface modification displayed improved stability under thermal, light, humidity and ambient conditions. This innovative strategy for ITO/NiOx interface modification efficiently promotes hole transportation and can be integrated with other interface engineering approaches, offering valuable insights for the development of highly efficient and stable IPSCs.

Controlling the Growth of Cs2PbX4 Nanostructures Enhances the Stability of Inorganic Cesium-Based Perovskite Solar Cells for Potential Low Earth Orbit Applications

Incorporating low-dimensional (LD) materials in perovskite solar cells (PSCs) for interfacial engineering is an effective approach to enhance device performance. However, the growth mechanisms for inorganic LD perovskite nanostructures in cesium-based systems via solution processing are underexplored. This work demonstrates the importance of controlling solvent evaporation dynamics during solution processing to modulate Cs2PbX4 nanomorphology. An evolution of growing Cs2PbX4 nanostructures is demonstrated on CsPbI2Br thin films. Cs2PbX4 nanostructures at CsPbI2Br grain boundaries introduce a passivation effect, improving interfacial quality with the hole transport layer (HTL). Systematic characterization reveals that careful engineering of LD nanostructures strongly impacts the optoelectronic properties of PSCs. Optimized CsPbI2Br/Cs2PbX4 heterostructures enhance the power conversion efficiency (PCE) from an average of 10.8% to 13.5%, achieving a 25% improvement over devices without interfacial engineering. Under a 100 h photovoltaic aging test, the PCE of the control device degraded by 30.7%, whereas the CsCl-treated devices retained 98% of their PCE from the start of the measurement. Post-proton-irradiated PSCs based on Cs2PbX4-modified CsPbI2Br retain up to 96% of their initial PCE of 12.2% after exposure to low Earth orbit-like conditions, maintaining a PCE of 11.7%. In contrast, the control device exhibits significant degradation, with the PCE dropping from 11.5% to 3.1%. These findings deepen our understanding of controlling the morphology of inorganic LD nanomaterials via a solution process. The promising stability of PSCs after interfacial engineering highlights their potential for robust performance under harsh conditions.

Photogenerated Carriers Surviving for Milliseconds in Perovskites under the Protection of Shallow Trap States

The performance of perovskite-based photovoltaic and light-emitting devices is susceptive to the interaction between charge carriers and trap states. The inherent trap state tolerance endows perovskite with a series of unprecedented properties; however, the underlying mechanisms remain poorly explored. Herein, we show, with a novel time-resolved stimulated emission spectroscopy approach, that photogenerated carriers are effectively prevented from internal nonradiative recombination and external luminescence quenching by shallow trap states. The photogenerated carriers survive for a period of >3 ms, 4 orders of magnitude longer than the submicrosecond photoluminescence lifetime. The surprisingly long-lived charge carriers can be quantitatively accounted for by a proposed model of trap state-assisted carrier protection (TSACP), which is consolidated by the results of confirmatory experiments on perovskites with varying chemical compositions and micronano structures. These findings shed light on the mechanism of carrier-trap state interaction, which will benefit for more effective defect engineering of perovskite materials and devices.

Coordination-driven assembly of a ferrocene-functionalized lead iodide framework with enhanced stability and charge transfer for photocatalytic CO2-to-CH3OH conversion

Hybrid lead halides are promising photocatalysts due to their high structural tunability and excellent photophysical properties, but their ionic structures suffer from instability in polar environments and suppressed charge transfer between lead halide units and organic components. Herein, we successfully incorporated a ferrocene-based light-harvesting antenna into a lead iodide framework by coordination-driven assembly. The π-conjugated Pb2+-carboxylate linkage affords synergistic interactions between [Pb2I2]2+ chains and ferrocene linkers, achieving broad visible absorption up to 612.7 nm and efficient ligand-to-metal charge transfer for spatial charge separation. This ultrastable framework combines strong visible-light absorption of ferrocene centers with excellent charge transport of lead halide units, achieving 6e- CO2 photoreduction to CH3OH coupled with ethanol oxidation. Mechanistic studies reveal that ferrocene photoexcitation followed by linker-to-metal charge transfer significantly enhances carrier accumulation, accelerating CH3O* intermediate formation as indicated by in situ spectroscopy and theoretical calculations.

Rational Interface Design Toward Mechanically Durable Flexible Perovskite Solar Cells

Owing to distinctive properties of lightweight, thin, high energy-to-mass ratio and bendability, flexible perovskite solar cells (f-PSCs) are expected to extend the application scenarios of photovoltaics, while the defective and fragile interface within the devices seriously restricted their mechanical stability and practical deployment. Herein, the origin of the flexibility of the perovskite lattice is explored and historic progress of the f-PSCs is briefly summarized. Then, the fracture mechanics of the f-PSCs and relevant mechanical characterizations are introduced. Recent strategies to boost the mechanical durability of the f-PSCs are systematically reviewed from the aspect of interface design, including the regulation of perovskite crystallization with optimum crystallinity and suppressed lattice strain, construction of grain boundary patches to eliminate the difference of mechanical properties between grain and grain boundaries, facilitating energy dissipation from fragile perovskite to adjacent elastic layers, and strengthening interfacial contact with improved fracture resistance. In the end, perspectives in the further development toward efficient and mechanically robust f-PSCs are provided.

Nanoconfined Metal Halide Perovskite Crystallization within Removable Polymer Scaffolds

Nanoconfining crystallization to access metastable polymorphs and prescribe crystal orientations typically involves filling inert nanoporous scaffolds with target compounds, resulting in isolated nanocrystals. Such crystal-scaffold composites are unsuitable for optoelectronic devices that require interconnected crystalline pathways for charge transport. Here, we reverse the order of fabricating crystal-scaffold composites by first electrospinning interconnected networks of amorphous methylammonium lead iodide (MAPbI3) precursor nanofibers, then introducing a poly(methyl methacrylate) (PMMA) scaffold by spin coating from an antisolvent for MAPbI3. PMMA suppresses MAPbI3 crystal blooming from the fiber surface during thermal annealing, instead promoting the formation of densely packed polycrystalline networks of MAPbI3 crystals at the fiber/PMMA interface. Near-IR photodetectors comprising densely packed MAPbI3 nanocrystals grown within a PMMA scaffold in a coplanar electrode geometry exhibit photocurrents up to 60 times larger than those comprising fibers annealed without PMMA. These results indicate that MAPbI3 crystals form a percolated network for charge carriers to flow through PMMA-confined fibers, resulting in significantly improved photodetector performance.

Perovskite CsCuClxBr3-x Microcrystals: Band Structure, Photochemical Stability, and Photocatalytic Properties

Although Pb-based metal halide perovskites (MHPs) have excellent photoelectric characteristics, its toxicity remains a limiting factor for its widespread application. In the paper, a series of CsCuClxBr3-x (x=1, 2, 3) MHPs microcrystals were developed and their hydrogen evolution performance in ethanol and HX (X=Cl, Br) were also studied. Among them, CsCuCl3 microcrystals exhibit high hydrogen evolution performance in both HX and ethanol, attributed to its longest average lifetime and suitable band structure. Additionally, the effect of different sacrificial agents on photocatalytic hydrogen production indicates that the photogenerated hole (h+) plays a critical role. MHPs can maintain a dynamic equilibrium of dissolution and precipitation in HX saturated aqueous solutions, thereby overcoming the stability issues associated with perovskite. The phase transition of CsCuClxBr3-x during photocatalysis is monitored by XRD technique. CsCuCl3 shows high stability in saturated HCl aqueous solution, and excellent photocatalytic performance with a hydrogen production rate of CsCuCl3 microcrystals reached 103.98 μmol g-1 at 210 min. Our study expands the development prospects of CsCuCl3 in the field of photocatalytic solar fuel generation.

A Decade of Lead Halide Perovskites for Direct-Conversion X-ray and Gamma Detection: Technology Readiness Level and Challenges

Over the past decade, lead halide perovskites (LHPs) have become a vibrant thrust in the field of direct conversion X-ray and gamma-ray radiation detectors, offering promising cost-effective and robust alternatives to traditional semiconductors. This review article chronicles the significant strides made since the inception of this field, emphasizing the material, structural, and functional advancements. It begins with an overview of the fundamental properties of perovskites that render them suitable for high-energy radiation detection, such as their high atomic number, prominent charge carriers' mobility and lifetime, and high resistivity. The review highlights key developments in material synthesis and processing techniques that have enhanced these detectors' stability, efficiency, and scalability. Furthermore, the review discusses the evolution of device architectures from single-channel photodiodes to complex multi-pixel arrays for imaging applications. The conclusion is focused on the remaining challenges that hamper the immediate progression of LHP radiation detectors to higher technology levels. This review is intended as a resource for academic researchers and industry stakeholders, summarizing the first decade of LHP detectors and forecasting the trajectory of this promising field, while remembering that forecasting the future trajectory, though challenging, is guided by current technological trends.

Advances in Single-Crystal Films: Synergistic Insights from Perovskites and Organic Molecules for High-Performance Optoelectronics

Semiconductor single-crystal thin films are crucial for the advancement of high-performance optoelectronic devices. Despite significant progress in fabricating perovskite and organic single-crystal films, interdisciplinary insights between these domains remain unexplored. This review aims to bridge this gap by summarizing recent advances in fabrication strategies for perovskite and organic molecular single-crystal films. Five preparation methods-solution-phase epitaxy, solid-phase epitaxy, meniscus-induced crystallization, antisolvent-induced crystallization, and space-confined growth-are analyzed with a focus on their principles, functional properties, and distinct advantages. By comparing these approaches across material systems, this review identifies transferable insights that can drive the development of large-scale, high-quality single-crystal films. Furthermore, the optoelectronic applications of these films are explored, including solar cells, photodetectors, light-emitting devices, and transistors, while addressing challenges such as scalability, defect control, and integration. This work highlights the importance of cross-disciplinary innovation and provides an effective pathway for integrating perovskite and organic molecular processing to advance the next generation of single-crystal film technologies.

ZrBr4-Mediated Phase Engineering in CsPbBr3 for Enhanced Operational Stability of White-Light-Emitting Diodes

The persistent operational instability of all-inorganic cesium lead halide (CsPbX3) perovskite nanocrystals (NCs) has hindered their integration into white-light-emitting diodes (WLEDs). This study introduces a transformative approach by engineering a phase transition from CsPbBr3 NCs to zirconium bromide (ZrBr4)-stabilized hexagonal nanocomposites (HNs) through a modified hot-injection synthesis. Structural analyses revealed that the ZrBr4-mediated phase transformation induced a structurally ordered lattice with minimized defects, significantly enhancing charge carrier confinement and radiative recombination efficiency. The resulting HNs achieved an exceptional photoluminescence quantum yield (PLQY) of 92%, prolonged emission lifetimes, and suppressed nonradiative decay, attributed to effective surface passivation. The WLEDs with HNs enabled a breakthrough luminous efficiency of 158 lm/W and a record color rendering index (CRI) of 98, outperforming conventional CsPbX3-based devices. The WLEDs exhibited robust thermal stability, retaining over 80% of initial emission intensity at 100 °C, and demonstrated exceptional operational stability with negligible PL degradation during 50 h of continuous operation at 100 mA. Commission Internationale de l'Éclairage (CIE) coordinates of (0.35, 0.32) validated pure white-light emission with high chromatic fidelity. This work establishes ZrBr4-mediated HNs as a paradigm-shifting material platform, addressing critical stability and efficiency challenges in perovskite optoelectronics and paving the way for next-generation, high-performance lighting solutions.

2D/3D Perovskite Surface Passivation-Enabled High-Detectivity Near-Infrared Photodiodes

Due to high responsivity and wide spectral sensitivity, metal halide perovskite photodiodes have a wide range of applications in the fields of visible light and near-infrared photodetection. Specific detectivity is an important quality factor for high-performance perovskite-based photodiodes, while one of the keys to achieving high detectivity is to reduce dark current. Here, 3-fluoro phenethylammonium iodide (3F-PEAI) was used to passivate the perovskite surface and form the two-dimensional (2D) perovskite on the three-dimensional (3D) perovskite surface. The as-fabricated passivated perovskite photodiodes with 2D/3D hybrid-dimensional perovskite heterojunctions showed two orders of magnitude smaller dark current, larger open circuit voltage and faster photoresponse, when compared to the control perovskite photodiodes. Meanwhile, it maintained almost identical photocurrent, achieving a high specific detectivity up to 2.4 × 1012 Jones and over the visible-near-infrared broadband photodetection. Notably, the champion photoresponsivity value of 0.45 A W-1 was achieved at 760 nm. It was verified that the 2D capping layers were able to suppress trap states and accelerate photocarrier collection. This work demonstrates strategic passivation of surface iodine vacancies, offering a promising pathway for developing ultrasensitive and low-power consumption photodetectors based on metal halide perovskites.

Ambipolar Charge Transport in Perovskite CsPbBr3 γ-Ray Detectors with Superior Uniformity and Spectral Resolution by Zone Refining Processing

Perovskite semiconductor cesium lead bromide (CsPbBr3) has demonstrated great promise as a new-generation gamma-ray detector. However, substantial challenges still present in reproducibly achieving optimal spectroscopic performance. The specific strategy for producing spectroscopic-grade CsPbBr3 crystals with high reproducibility and uniformity are still not clarified. Herein, efficient zone refining processing is developed for CsPbBr3 crystals that facilitates impurity segregation to achieve an ultrahigh purity level of ≈1.42 ppm, therefore lowers trap density and balances charge transport. In a typical 30 mm diameter zone-refined CsPbBr3 ingot, all wafers exhibited remarkable energy resolutions of 6-12% and 3-8% for 241Am and 57Co γ-rays under comparable electric fields. The crystals also exhibited an ambipolar charge transport characteristic, resemble to elemental semiconductors, with equivalent hole and electron mobility-lifetime products averaging 5.42 × 10-3 and 2.27 × 10-3 cm2∙V-1, respectively. Consequently, over 95% of wafers achieved energy resolutions below 5% whereas 70% exceeded 3% for 137Cs γ-rays, demonstrating exceptional reproducibility and uniformity. Notably, a champion energy resolution of 1.3% with an outstanding photopeak-to-Compton (P/C) ratio of ≈5.3 is attained in an ambipolar planar detector. It is anticipated that this work shall expedite scalable manufacturing and practical applications of CsPbBr3 detectors.

Coupling Light into Memristors: Advances in Halide Perovskite Resistive Switching and Neuromorphic Computing

Resistive switching memristor is an emerging nonvolatile memory technology designed to overcome the physical limitations of conventional systems and the performance bottleneck of the von Neumann architecture. Notably, halide perovskite (HP)-based memristors have gained significant attention in recent years due to their unique ionic migration behavior and exceptional photoelectric properties. This review highlights HP-based resistive switching, focusing on its recent developments in coupling light into memristors and discussing its implications for neuromorphic computing. The mechanisms of resistive switching are explored alongside the role of HP photoelectric properties in enhancing switching dynamics. The advantages and applications of light-coupled resistive switching, including reduced switching voltage, enhanced operation reliability, multilevel switching capability, and the development of light-integrated artificial synapses are discussed comprehensively. By fully harnessing the exceptional optoelectronic properties of HPs, this emerging field may pave the way for innovative approaches to memory technologies and light-responsive neuromorphic systems.

Simultaneous Halides Oxidation Inhibition and Defects Passivation for Efficient and Stable Perovskite Solar Cells

Despite significant progress in improving the photovoltaic efficiency of perovskite solar cells (PSCs), achieving long-term operational stability remains challenging for their commercialization. Light-induced halide ion migration causes instability, oxidizing iodide into iodine. Elevated temperatures exacerbate this issue, resulting in irreversible device degradation. Here, ammonium oxalate (AO) is introduced as an additive to the perovskite precursor to prevent both the degradation of the perovskite precursor and the photo-induced degradation pathway to formamidinium iodide and PbI2 in perovskite films. AO stabilizes the precursor by inhibiting the oxidation of iodide ions (I-) and passivates charged traps through coordination and hydrogen bonding interactions, thereby enhancing crystallinity and reducing defects within the resultant perovskite films. This leads to the achievement of a higher-quality perovskite film with a low trap density and an extended carrier lifetime. In addition, the oxidation of I- within the perovskite film is inhibited, reducing the corrosion of I2 on the silver electrode and enhancing the long-term operating stability of the photovoltaic device. Consequently, the champion power conversion efficiency (PCE) of PSCs is increased from 22.19% to 24.82%. Meanwhile, the air, thermal, and light stability are also enhanced.

Scalable Impregnation Method for Preparing a Self-Assembled Monolayer in High-Performance Vapor-Deposited Lead-Halide Perovskite Solar Cells

The power conversion efficiency (PCE) of inverted lead-halide perovskite solar cells (PSCs) via vapor deposition has undergone significant enhancement through the incorporation of a self-assembled monolayer (SAM) serving as the hole transport layer. To achieve high-performance PSCs, the SAM layer needs to maintain a dense and high-coverage configuration during the fabrication process. Our investigation revealed that during solid-vapor reaction, conditions of high temperature and low pressure can potentially lead to the migration of SAM molecules, particularly those adsorbed on the surface but have not yet formed covalent bonds. In this study, to overcome this limitation, we have developed an impregnation process for mixed SAM molecules with (4-(7H-dibenzo[c,g]carbazol-7-yl)butyl)phosphonic acid (4PADCB) and glycine hydrochloride (GH), which reduces the agglomeration of SAM molecules and enhances their strong anchoring ability with the substrate, thereby maintaining an extremely high coverage rate even in the high-temperature and low-pressure environment of solid-vapor reactions. Consequently, champion efficiencies of 22.15% (0.16 cm2) and 19.18% (5 cm × 5 cm module) are achieved, which is the highest record for inverted PSCs based on vapor deposition. Moreover, the impregnation process of the SAM layer has the advantages of reusability, good uniformity, and low cost, which has very broad commercial prospects.

Deriving mobility-lifetime products in halide perovskite films from spectrally and time-resolved photoluminescence

Lead-halide perovskites are semiconductor materials with attractive properties for photovoltaic and other optoelectronic applications. However, determining crucial electronic material parameters, such as charge-carrier mobility and lifetime, is plagued by a wide range of reported values and inconsistencies caused by interpreting and reporting data originating from different measurement techniques. Here, we propose a method for the simultaneous determination of mobility and lifetime using only one technique: transient photoluminescence spectroscopy. By measuring and simulating the decay of the photoluminescence intensity and the redshift of the photoluminescence peak as a function of time after the laser pulse, we extract the mobility, lifetime, and diffusion length of halide perovskite films. With a voltage-dependent steady-state photoluminescence measurement on a cell, we relate the diffusion length to the external voltage and quantify its value at the maximum power point.

Unassisted self-healing photocatalysts based on Le Chatelier's principle

Self-healing is a fundamental ability inherent in humans, plants, and other living organisms. To date, a variety of materials with self-healing properties have been developed. However, these materials usually require external inputs such as electric potentials or healing agents to initiate or promote self-healing reactions. Herein, we present a novel self-healing mechanism that operates without any external input, utilizing the dynamic equilibrium between the solid-state and dissolved materials. We employed organic-inorganic perovskites to validate our strategy. Single-particle spectroscopy and imaging demonstrated the spontaneous self-healing of perovskites after photodamage under dynamic equilibrium conditions. Furthermore, we found that perovskites can generate hydrogen in both healed and damaged states. Remarkably, the perovskites exhibited hydrogen generation over four cycles of photodamage and self-healing. The proposed concept and experimental results provide valuable insights for the development of energy conversion and storage systems with improved long-term durability.

Decoding recombination dynamics in perovskite solar cells: an in-depth critical review

The remarkable optoelectronic properties of metal halide perovskites (MHPs) have established them as highly promising photovoltaic absorber materials, propelling the rapid advancement of perovskite solar cells (PSCs) that outperform many traditional alternatives in terms of power conversion efficiency (PCE). However, despite their advancements, PSC devices encounter significant non-radiative recombination losses, encompassing trap-assisted (Shockley-Read-Hall) recombination in bulk and interfaces of PSCs, which restricts their open-circuit voltage (VOC) and overall PCE, dragging it below the Shockley-Queisser (SQ) limit. The ongoing debate regarding the role of grain boundary (GB) recombination, whether it primarily manifests as bulk or surface recombination, has spurred extensive research aimed at elucidating these mechanisms. This review provides a critical comprehensive analysis of the thermodynamic correlations related to VOC losses, bridging the gap between the theoretical SQ limit and practical device performance. Subsequently, it delves into recent findings that aim to decipher the multifaced nature and origin of radiative and non-radiative recombination-induced losses within the device stack, assessing their impacts on overall performance. Furthermore, this review emphasizes the application of advanced machine learning techniques to discern dominant recombination mechanisms in PSCs. Finally, it summarizes the notable advanced strategies to mitigate undesirable non-radiative recombination losses, which pave the way to the thermodynamic efficiency limit.

Advances in hot carrier relaxation dynamics of perovskites with ultrafast time-resolved detection

Perovskite (PVK) materials have been widely studied and widely used in photoelectric conversion devices due to their unique crystal structure, many interesting physical and chemical properties and low manufacturing cost. Despite extensive research, challenges remain in fully understanding the dynamic processes of carrier recombination, separation, transport and dynamic evolution of defect states, which are critical to device performance. Addressing these gaps is essential for the development of high-speed optoelectronic devices. The development of high-speed devices requires a full understanding of the properties of materials, especially the dynamic processes such as carrier recombination, separation, and transport, which often play a vital role in the performance of devices. Therefore, in order to better understand and control the behavior of photo-induced hot carriers (HC), ultrafast laser detection technology is applied to the study of PVK materials, which can observe and measure the generation, transmission, and recombination of photo-induced HCs in real time to reveal their dynamic behavior and photoelectric properties. This paper summarizes the latest research progress of ultrafast carrier dynamics in all-inorganic halide PVKs, double PVKs and organic-inorganic halide PVKs to fully understand their carrier relaxation, recombination, transfer, and other behaviors. Additionally, this review highlights emerging trends and unresolved issues in HC dynamics, aiming to provide a roadmap for future studies in this area. It is expected that with the help of the relevant physical mechanism of HC relaxation dynamics obtained here, breakthroughs will be made in improving and regulating the photoelectric conversion efficiency and the corresponding ultrafast light response devices in the future.

Efficient Hybrid-Functional-Based Force and Stress Calculations for Periodic Systems with Thousands of Atoms

We present an efficient linear-scaling algorithm for evaluating the analytical force and stress contributions derived from the exact-exchange energy, a key component in hybrid functional calculations. The algorithm, working equally well for molecular and periodic systems, is formulated within the framework of numerical atomic orbital (NAO) basis sets and takes advantage of the localized resolution-of-identity (LRI) technique for treating the two-electron Coulomb repulsion integrals. The linear-scaling behavior is realized by fully exploiting the sparsity of the expansion coefficients resulting from the strict locality of the NAOs and the LRI ansatz. Our implementation is massively parallel, and enables efficient structural relaxation based on hybrid density functionals for bulk materials containing thousands of atoms. In this work, we will present a detailed description of our algorithm and benchmark the performance of our implementation using illustrating examples. By optimizing the structures of the pristine and doped halide perovskite material CsSnI3 with different functionals, we find that in the presence of lattice strain, hybrid functionals provide a more accurate description of the stereochemical expression of the lone pair.

A Close-Space Fast Nucleation Strategy toward High-Efficiency Perovskite Light-Emitting Diodes

Halide perovskite light-emitting diodes (PeLEDs), considered as potential candidates for future displays, face significant limitations in their external quantum efficiency (EQE) due to an uncontrollable nucleation and crystallization process. Herein, a close-space inverted annealing (CSIA) strategy is developed to achieve fast nucleation and obtain a more uniform perovskite film with larger crystal domains and much lower defect centers. The increased surficial temperature and quick solvent evaporation in the CSIA method result in the fast formation of numerous large nuclei and solvate intermediates at the initial stage, which effectively guide crystal growth into large domains, facilitated by the residual solvent. The CSIA-processed PeLED achieves a peak EQE of 25.8%, which is among the best values of near-infrared devices. Moreover, it is applicable to perovskite-emitting layers with different defect passivation agents. This straightforward approach highlights a great opportunity to boost the performance and commercialization of perovskite optoelectronic devices.

Architectural Innovations in Perovskite Solar Cells

Meeting future energy demands with sustainable sources like photovoltaics (PV) presents significant land and logistical challenges, which can be mitigated by improving PV power conversion efficiency (PCE) and decentralized solutions like building-integrated photovoltaics and solar-integrated mobility systems (e.g., Unmanned Aerial Vehicles (UAVs)). Metal Halide Perovskites Solar Cells (MH-PSCs) provide a transformative, low-cost solution for high-efficiency PV with diverse compositions, exceptional optoelectronic properties, and low-temperature, solution-based processability. Conventionally the MH-PSCs are fabricated in "p-i-n" or "n-i-p" configuration on glass-Transparent Conductive Oxide (TCO) substrates. While glass-based Perovskite Solar Cells (PSCs) have achieved remarkable efficiencies, their limited scalability, high areal-weight, and mechanical rigidity greatly limit their usage in wearables electronics, BIPVs, and e-mobility applications. Addressing these challenges requires "targeted architectural innovations" in MH-PSCs, tailored to specific applications, to drive their practical deployment forward. This study reviews four innovative PSC architectures-Interdigitated Back Contact (IBC) PSCs, Lateral Configuration (LC) PSCs, Fiber-Shaped (FS) PSCs, and Substrate-Configuration (SC) PSCs-highlighting their design advancements for enhanced efficiency, flexibility, lightweight, and application-specific integration. Importantly, the review discusses the precise engineering required in each layer of these architectural innovations to ensure compatibility, efficient charge transport, durability, and scalability while optimizing performance, while also identifying key challenges and outlining directions for future R&D.

Ultra-Flexible Pixelated Perovskite Photodetectors Enabled by Honeycomb Polymer Grids for High-Resolution Imaging

A nature-inspired fabrication method based on a photolithography-free flexible polymer grid is reported for high-resolution pixelation of perovskite photodiode arrays with exceptional mechanical ductility and a morphology resembling that of natural compound eyes. The resulting pixelated perovskite photosensitive layer has a ≈1 µm pixel size with 2000 Pixels per inch (PPI) resolution when fully assembled as a photodetector array, delivering a detectivity of >1013 Jones while providing cross-talk free imaging. Using a polymer grid effectively releases stress on the perovskite platform, greatly increasing the mechanical agility of the otherwise brittle perovskite film. This novel fabrication methodology and device design offer new possibilities for applications in robotics, biomedical imaging, and virtual and augmented reality.

Three-Dimensional High-Resolution Laser Lithography of CsPbBr3 Quantum Dots in Photoresist with Sub-100 nm Feature Size

Perovskite quantum dots (PQDs), with their excellent optical properties, have become a leading semiconductor material in the field of optoelectronics. However, to date, it has been a challenge to achieve the three-dimensional high-resolution patterning of perovskite quantum dots. In this paper, an in situ femtosecond laser-direct-writing technology was demonstrated for three-dimensional high-resolution patterned CsPbBr3 PQDs using a two-photon photoresist nanocomposite doped with the CsPbBr3 perovskite precursor. By adjusting the laser processing parameters, the minimum line width of the PQDs material was confirmed to be 98.6 nm, achieving a sub-100 nm PQDs nanowire for the first time. In addition, the fluorescence intensity of the laser-processed PQDs can be regulated by the laser power. Our findings provide a new technology for fabricating high-resolution display devices based on laser-direct-writing CsPbBr3 PQDs materials.

Discovery of Perovskite Cosolvency and Undoped FAPbI3 Single-Crystal Solar Cells Fabricated in Ambient Air

We report the cosolvency effect of formamidinium lead triiodide (FAPbI3) in a mixture of γ-butyrolactone (GBL) and 2-methoxyethanol (2ME), a phenomenon where FAPbI3 shows higher solubility in the solvent blend than in either alone. We found that FAPbI3 exhibits 10× higher solubility in 30% 2ME in GBL than in 2ME alone and 40% higher solubility than in GBL alone at 90 °C. This enhanced solubility is attributed to the disruption of the hydrogen bonding network within 2ME, allowing its hydroxyl and ether groups to interact more freely with the solute. Leveraging this phenomenon, we grew phase-stable α-FAPbI3 thin single crystals under ambient air conditions with no doping. Compared to conventional cesium-doped FAPbI3, the undoped FAPbI3 single-crystal films exhibited lower defect densities and enhanced charge retention and transfer while also avoiding phase segregation linked to cesium incorporation. Solar cells fabricated with these ambient-air-grown single-crystal films achieved an efficiency of 21.56% (17.72% for cesium-doped FAPbI3), retaining 90% of performance after six months of storage. These findings advance our understanding of perovskite solubility in solvent blends and offer an efficient pathway for producing stable, high-efficiency FAPbI3 single-crystal solar cells through ambient air fabrication, overcoming the limitations of doping.

On the Interplay of Electronic and Lattice Screening on Exciton Binding in Two-Dimensional Lead Halide Perovskites

We use path integral Monte Carlo to study the energetics of excitons in layered, hybrid organic-inorganic perovskites in order to elucidate the relative contributions of dielectric confinement and electron-phonon coupling. While the dielectric mismatch between polar perovskite layers and nonpolar ligand layers significantly increases the exciton binding energy relative to their three-dimensional bulk crystal counterparts, formation of exciton polarons attenuates this effect. The contribution from polaron formation is found to be a nonmonotonic function of the lead halide layer thickness, which is clarified by a general variational theory. Accounting for both of these effects provides a description of exciton binding energies in good agreement with experimental measurements. By studying isolated layers and stacked layered crystals of various thicknesses, with ligands of varying polarity, we provide a systematic understanding of the excitonic behavior of this class of materials and how to engineer their photophysics.

Innovative Design and Synthesis of Fullerene-Terpyridine Derivatives for Enhanced Electron Transport in Inverted Perovskite Solar Cells

In this study, three fullerene derivatives─C60tBu, C60TPY, and C60TPY-Cl─were synthesized and investigated as additives in PC61BM-based electron-transporting layers (ETLs) for inverted perovskite solar cells (PVSCs). The incorporation of C60tBu and C60TPY into the ETLs led to improved ETL morphology and passivation of crystal defects on the surface of the methylammonium lead iodide (MAPbI3) layer. This defect passivation enhanced crystal quality, increased UV-vis absorption, reduced charge recombination, and improved electron mobility in the C60tBu- and C60TPY-based PVSCs. The passivation effect of C60TPY, which contains a 2,2':6',2″-terpyridine (TPY) unit, was found to be superior to that of C60tBu, which features a t-butyl ester group. As a result, PVSCs utilizing C60TPY exhibited enhanced photovoltaic performance compared to those incorporating C60tBu. To further investigate the contribution of the TPY moiety to the passivation effect, C60TPY was neutralized with HCl to afford C60TPY-Cl. As anticipated, the protonation of the TPY group in C60TPY-Cl resulted in poorer ETL morphology and diminished defect passivation within the MAPbI3 layer. Consequently, no improvement in photovoltaic properties was observed for PVSCs treated with C60TPY-Cl. The architecture of the inverted PVSCs doped with fullerene derivatives consisted of indium tin oxide/NiOx/MAPbI3/fullerene derivative: PC61BM/bathocuproine/Ag. Among the fullerene-based additives, C60TPY demonstrated the highest photovoltaic performance, achieving a power conversion efficiency (PCE) of 20.10%, an open-circuit voltage of 1.07 V, a short-circuit current density of 24.85 mA cm-2, and a fill factor of 75.6%. Furthermore, the C60TPY-based PVSC retained 80% of its initial PCE after 450 h of storage under ambient conditions (30 °C, 40% relative humidity).

Stable self-powered X-ray detection with a low detection limit using a green halide hybrid perovskite ferroelectric crystal

Lead halide hybrid perovskite ferroelectrics show great potential in the field of self-powered X-ray detection due to their excellent X-ray absorption, high carrier mobility, large carrier lifetime, and interesting ferroelectricity. Nonetheless, the toxicity of lead raises concerns regarding safety for humans and the environment, which limits their practical applicability. Herein, we successfully realized stable self-powered X-ray detection with a low detection limit using a lead-free halide hybrid perovskite ferroelectric crystal, [H2mdap]BiBr5 (1, H2mdap = N-methyl-1,3-diaminopropanium), driven by the switchable spontaneous polarization (P s). Specifically, a remarkable switchable ferroelectric-photovoltaic (FE-PV) effect and excellent open-circuit photovoltage under X-ray irradiation endow 1 with a self-powered detection capability. Strikingly, the 1 detector shows a relatively high sensitivity of 79.0 μC Gy-1 cm-2 under 22 keV X-rays and achieves a low detection limit of 28 nGy s-1 at zero bias, much lower than that of the regular medical diagnosis (∼5.5 μGy s-1). Additionally, 1 also shows good operational stability, which may benefit from a stable structure and high activation energy (E a). This study successfully demonstrates self-powered X-ray detection in 1D lead-free ferroelectric materials, which opens up new possibilities for safe and stable X-ray detection.

Eco-friendly synthesis and stability analysis of CsPbBr3and poly(methyl methacrylate)-CsPbBr3films

This study presents an eco-friendly mechanochemical synthesis of cesium lead bromide (CsPbBr3), eliminating the need of organic solvents and high temperatures. The synthesized CsPbBr3powder is used to fabricate poly(methyl methacrylate) (PMMA)-CsPbBr3films and CsPbBr3nanocrystals (NCs). The photoluminescence (PL) peaks of the emission light are centered at 541 nm, 538 nm, and 514 nm for the CsPbBr3powder, PMMA-CsPbBr3films, and CsPbBr3NCs, respectively, correlating with crystal sizes of 0.96, 0.56, and 0.12μm, respectively. The PL lifetime analysis reveals decay times (τ1,τ2) of (4.18, 20.08), (5.7, 46.99), and (5.81, 23.14) in the units (ns, ns) for the CsPbBr3powder, PMMA-CsPbBr3films, and CsPbBr3NCs, respectively. The PL quantum yield of the CsPbBr3NCs in toluene is 61.3%. Thermal activation energies for thermal quenching are 217.48 meV (films) and 178.15 meV (powder), indicating improved thermal stability with the PMMA encapsulation. The analysis of the PL intensity decay from water diffusion in the PMMA-CsPbBr3films yields 1.70 × 10-12m2s-1for the diffusion coefficient of water, comparable to that for water diffusion in pure PMMA. This work demonstrates a scalable, sustainable strategy for CsPbBr3synthesis and stability enhancement for optoelectronic applications.

Open micro-combinatorial analysis systems of crystal growth critical points of a π-conjugated molecule in ionic liquid nanoliter droplets

Crystal engineering methodologies based on reproducible and high-throughput fabrication of high-quality single crystals have attracted much attention. Crystal formation and growth are governed by crystal growth theory. The driving force of crystallization is systematically represented with phase diagrams. However, constructing phase diagrams usually requires relatively large quantities of samples (milligrams to grams) and substantial time (weeks to months) to evaluate many conditions. Therefore, an easy and quick methodology to obtain phase diagrams, revealing critical conditions for valuable samples, is required. Here, we proposed a new method to obtain phase diagrams based on nanoliter droplet arrays of nonvolatile ionic liquids prepared by inkjet printing. Anthracene derivatives and 1-octyl-4-methylpyridinium derivatives were used as the solute and solvent, respectively. Optimization of ejection conditions, such as applied voltage, frequency, pulse width, and head temperature, enabled the formation of a 0.5 nL droplet per ejection. Inkjet printing under these conditions formed nanodroplet arrays on substrates at a droplet-patterned density of ca. 50 dots per cm2. The volume of each patterned droplet was varied from 10 to 100 nL by changing the number of ejections. The dissolution temperature of anthracene at each concentration was obtained at a heating rate of 0.2 °C min-1. This heating rate was found to be 10 times faster than the conventional technique. The same phase diagram as that prepared by the conventional technique was obtained in the range of 75-300 mM. The standard deviation of the dissolution temperatures was 0.8 °C (2.5%). This technique will facilitate the crystallization of multiple and valuable samples.

Ultralow trap density FAPbBr3 perovskite films for efficient light-emitting diodes and amplified spontaneous emission

Solution-processed metal halide perovskites are widely studied for their potential in high-efficiency light-emitting diodes, yet they are facing several challenges like insufficient brightness, short operational lifetimes, and reduced power conversion efficiency under practical operation conditions. Here, we develop an interfacial amidation reaction on sacrificial ZnO substrates to produce perovskite films with low trap density (1.2 × 1010 cm-3), and implement a device structure featuring a mono-molecular hole-injection layer and an all-inorganic bi-layered electron-injection layer. This design leads to green perovskite light-emitting diodes with a brightness of ~ 312,000 cd m-2, a half-lifetime of 350 h at 1000 cd m-2, and a power conversion efficiency of 15.6% at a current density of 300 mA cm-2. Furthermore, the perovskite films show a low amplified spontaneous emission threshold of 13 μJ cm-2. Thus, our approach significantly advances the performance of green perovskite light-emitting diodes and opens up an avenue toward perovskite-based electrically pumped lasers.

First-principles study of Ga2Ge2S3Se3 monolayer: a promising photocatalyst for water splitting

Recently, the quaternary Janus monolayers with the formula A2B2X3Y3 have been shown to be promising candidates for optoelectronic applications, especially in the photocatalytic water splitting reaction. Therefore, first-principles calculations were employed to investigate the photocatalytic properties of Ga2Ge2X3Y3 (X and Y represent S, Se or Te atoms) monolayers. The Ga2Ge2S3Se3 and Ga2Ge2Se3Te3 monolayers exhibit dynamic and thermal stability, supported by high cohesive energies (3.78-4.20 eV) and positive phonon dispersion. With a moderate Young's modulus (50.02-65.31 N m-1) and high Poisson's ratio (0.39-0.41), these monolayers offer a balance of stiffness and flexibility, making them suitable for flexible electronic applications. Especially, the difference in work function of 0.27 eV induces an intrinsic electric field in the Ga2Ge2S3Se3 monolayer, making the electronic structure of this material be suitable for the photocatalytic water splitting process. With light irradiation, the oxygen evolution reaction (OER) happened simultaneously, producing electrons and H+ protons for the hydrogen evolution reaction (HER) to happen at a low potential barrier. Moreover, the Ga2Ge2S3Se3 monolayer has a high absorption rate α(ω) of 105-106 cm-1 and a high electron mobility of 430.82-461.50 cm2 V-1 s-1. These characteristics result in a good solar-to-hydrogen of the Ga2Ge2S3Se3 monolayer (14.80%) which is promising for use in photon-driven water splitting.

A high-performance X-ray detector based on large-size perovskite MAPbI3 single crystals grown by environmentally friendly solvents and advanced systems

In this paper, we report a novel hermetically sealed and precisely temperature-controlled growth system that grows MAPbI3 single crystals up to a size of 60 × 48 × 22 mm3. The grown crystals have lower defects and higher quality. It is expected to facilitate the commercialization of perovskite single crystals for optoelectronic applications.

Exploring Lead-Free (Guanidinium)3Bi2Br9 Perovskite-Type Crystal toward X-Ray Detection with an Ultralow Detection Limit

Lead-free bismuth halogen perovskites have emerged as a promising candidate for high-performance X-ray detection, owing to their unique properties of bulk resistivity, significant X-ray absorption capabilities and diminished ion migration. Herein, using the facile low-temperature solution method, we obtained a large-size single crystal of (guanidinium)3Bi2Br9 (GBB), which adopts a zero-dimensional (0D) inorganic perovskite-like framework. The as-grown crystals show high resistivity (3.51×1012 Ω cm), low trap density (1.14×1010 cm-3) and large carrier mobility-lifetime product (μτ=1.13×10-3 cm2 V-1) under X-ray irradiation. Strikingly, the X-ray detectors fabricated on GBB single crystals exhibit notable performances including low dark current drift, high sensitivity of ~1645.7 μC Gyair -1 cm-2, and ultralow detection limit of ~0.85 nGyair s-1. This detection limit is among the lowest level for the reported 0D perovskite X-ray detectors. This study illuminates the prospective research into novel lead-free hybrid perovskites for the advancement of high-performance detectors of irradiation.

MAPbX3 Perovskite Single Crystals for Advanced Optoelectronic Applications: Progress, Challenges, and Perspective

Perovskite single crystals have garnered significant attention due to their impressive properties in optoelectronic applications, including long carrier diffusion lengths, low trap-state densities, and enhanced stability. Methylamino lead halide perovskite (MAPbX3, where X is a halogen such as Cl, Br, or I) is a notable example of a metal halide perovskite with desirable properties and ideal cubic perovskites with a tolerance factor between 0.9 and 1.0. MAPbX3 has adjustable bandgap, high thermal and chemical stability, and excellent light absorption capacity. Here the unique characteristics of MAPbX3, including molecular structure, optical absorption properties, and carrier transport of MAPbX3 single crystals are summarized. Universal growth technologies for MAPbX3 single crystals, including inverse temperature crystallization, anti-solvent evaporation crystallization, solvent evaporation method, and single-crystalline thin film, including epitaxial method and space limiting method, are briefly introduced. Additionally, a comprehensive review of MAPbX3 single crystals in various optoelectronic device applications, including photodetectors, X-ray detectors, light-emitting diodes, lasers, and solar cells is mainly discussed. Finally, the current challenges and future prospects of the large-scale preparation and growth of MAPbX3 single crystals are put forward. With the continuous progress of photoelectric technology, more innovative photoelectric applications in the future are expected to bring more convenience and progress.

Stress Release of Single Crystal Arrays Bridged by SAM Interface Toward Highly Mechanically Durable Flexible Perovskite NIR Photodetector

Perovskite photodetectors with superior optoelectronic properties, lightweight, and compatibility with flexible substrates have attracted much attention in wearable electronics. However, the large bandgap, inherent brittleness, poor environmental stability, and weak interfacial adhesion interaction between perovskites and substrates hinder the application of near-infrared (NIR) wearable devices. Herein, a universal strategy to enhance the performance and mechanical stability of flexible perovskite NIR photodetector arrays is demonstrated through a combination of mussel-inspired self-assembled monolayer (SAM) bridging interface and precise modulation of the nano-array size, which enables to significantly increase interfacial adhesion, crystallinity, crystallographic orientation, and reduce mechanical stresses of perovskite single-crystal arrays. Moreover, inserting paddle-wheel metal-organic cluster ligands lead to an unprecedented small bandgap of 1.04 eV, enhanced lattice rigidity, and environmental stability for 2D perovskite. The flexible perovskite NIR photodetector arrays with superior mechanical robustness and record NIR performance are revealed with a maximum response wavelength of 1050 nm, a responsivity of 1.66 A W-1, detectivity of 6.19 × 1012 Jones, high fidelity imaging, and extra-long environmental stability. This work pioneers a new insight into the integration of high-performance and mechanically durable perovskite flexible wearable devices.

Remote epitaxial crystalline perovskites for ultrahigh-resolution micro-LED displays

The miniaturization of light-emitting diodes (LEDs) is pivotal in ultrahigh-resolution displays. Metal-halide perovskites promise efficient light emission, long-range carrier transport and scalable manufacturing for bright microscale LED (micro-LED) displays. However, thin-film perovskites with inhomogeneous spatial distribution of light emission and unstable surface under lithography are incompatible with the micro-LED devices. Continuous single-crystalline perovskite films with eliminated grain boundaries, stable surfaces and optical homogeneity are highly demanded for micro-LEDs, but their growth and device integration remain challenging. Here we realize the remote-epitaxy growth of crystalline perovskite films, enabling their seamless integration into micro-LEDs with a pixel size down to 4 μm. By incorporating a subnanometre graphene interlayer, we enable remote epitaxy and transfer of perovskites with relaxed strain. These micro-LEDs exhibit a high electroluminescence efficiency of 16.7% and a high brightness of 4.0 × 105 cd m-2. Such high performance stems from suppressed defects and efficient carrier transport in epitaxial perovskites with high crystallinity, relaxed strain and hundreds-of-nanometres thickness. The free-standing perovskites can be integrated with commercial electronic planes for independent and dynamic control of each pixel, thus facilitating both static image and video display. With these findings, we envision on-chip perovskite photonic sources such as ultracompact lasers and ultrafast LEDs.

Manipulation of Metal Halide Perovskite: Photoelectric Conversion or Light Emission?

Metal halide perovskites (MHPs) display a range of superior photophysical properties, rendering them promising as a candidate for the active medium of high-efficiency photovoltaic and electroluminescence devices. In order to maximize their efficacy in photoelectric conversion or light emission, it is essential to regulate the charge separation efficiency of MHPs in a desired manner. Herein, we demonstrate that the extent of charge separation can be effectively manipulated upon thermal annealing treatment on MHPs. As the annealing time is extended from 10 to 30 min, the accumulation of excess lead halides is observed at the boundaries of MHP grains, resulting in the construction of a quasi-Type II band alignment between the lead halide and the MHP. This facilitates the separation of electron-hole pairs, reducing the exciton binding energy from approximately 102 meV to a level comparable with kBT. Our findings elucidate the transition of MHPs from a light-emission material to a photoelectric-conversion material along with continuous heating treatment, which is anticipated to guide the flexible regulation of MHPs to meet the requirements of specific practical applications.

Extending Carrier Lifetimes of Metal Halide Perovskites by Defect Passivation with Alkaline Earth Metals: A Time-Domain Study

Intrinsic defects that serve as non-radiative recombination centers significantly accelerate charge and energy losses in hybrid organic-inorganic perovskites. The defect IMA, formed by replacing an MA with an I in MAPbI3 (MA = CH3NH3+), creates an I trimer that produces a deep electron trap state. Non-adiabatic (NA) molecular dynamics simulations demonstrate that an excited conduction band electron is rapidly captured by this electron trap within 100 ps, followed by recombination with a valence band hole within 1 ns, which is 3 times faster than that in the pristine system. Doping with interstitial Sr and Ba eliminates the electron trap state by breaking the I trimer, thereby restoring the electron-hole recombination across the bandgap to durations up to 3.20 and 4.36 ns, respectively. The delayed recombination is attributed to decreased NA coupling and a shortened decoherence time. These findings provide critical insights into perovskite defect passivation strategies with alkaline earth metals.

Multifunctional acetoacetanilide additive strategy for enhanced efficiency and stability in perovskite solar cells

Perovskite solar cells (PSCs) have garnered tremendous interest for their cost-effective solution-based fabrication process and impressive power conversion efficiency (PCE). The performance and stability of PSCs are closely tied to the quality of the perovskite film. Additive engineering has emerged as a highly effective strategy to achieve stable and efficient PSCs. In this study, acetoacetanilide (AAA), containing amide and carbonyl groups, is introduced for the first time as a multifunctional agent to the MAPbI3 precursor solution. Carbonyl groups in AAA coordinate with lead ions (Pb2+), influencing the crystallization process by binding to Pb2+ ions through lone pair electrons. It helps to control crystallization kinetics and passivates defects caused by under-coordinated Pb2+ ions. Simultaneously, the amide groups strongly interact with iodide ions (I-), stabilizing them and suppressing ion migration, which reduces defect vacancies in the perovskite structure. Incorporating AAA led to a significant improvement in PCE, increasing from 16.93% in the untreated device to 20.1% in the AAA-treated devices. Furthermore, the AAA-treated devices showed more stability behavior against humidity and light. These findings underscore the potential of AAA as a high-performing additive for advancing the PCE and stability of PSCs.

Steady state and transient absorption spectroscopy in metal halide perovskites

Metal halide perovskites (MHPs) have emerged as the most promising materials due to superior optoelectronic properties and great applications spanning from photovoltaics to photonics. Absorption spectroscopy provides a broad and deep insight into the carrier dynamics of MHPs, and is a critical complement to fluorescence and scattering spectroscopy. However, absorption spectroscopy is often misunderstood or underestimated, being seen as UV-vis spectroscopy only, which can lead to various misinterpretations. In fact, absorption spectroscopy is one of the most important branches of spectroscopic techniques (others including fluorescence and scattering), which plays a critical role in understanding the electronic structure and optoelectrical dynamics of MHPs. In this tutorial, the basic principles of various types of absorption spectroscopy as well as their recent developments and applications in MHP materials and devices are summarized, covering comprehensive advances in steady state and transient absorption spectroscopy. Given the significance of absorption spectroscopy in directing the design of different optoelectronic applications of MHPs, this tutorial will comprehensively discuss absorption spectroscopy, covering wavelengths from optical to terahertz (THz) and microwave, and timescales from femtoseconds to hours, and it specifically focuses on time-dependent steady-state and transient absorption spectroscopy under light illumination bias to study MHP materials and devices, allowing researchers to select suitable characterization techniques.

Spatially Isomeric Fulleropyrrolidines Enable Controlled Stacking of Perovskite Colloids for High-Performance Tin-Based Perovskite Solar Cells

The advancement of tin-based perovskite solar cells (TPSCs) has been severely hindered by the poor controllability of perovskite crystal growth and the energy level mismatch between the perovskite and fullerene-based electron transport layer (ETL). Here, we synthesized three cis-configured pyridyl-substituted fulleropyrrolidines (PPF), specifically 2-pyridyl (PPF2), 3-pyridyl (PPF3), and 4-pyridyl (PPF4), and utilized them as precursor additives to regulate the crystallization kinetics during film formation. The spatial distance between the two pyridine groups in PPF2, PPF3, and PPF4 increases sequentially, enabling PPF4 to interact with more perovskite colloidal particles. These interactions effectively enlarge the precursor colloid size and decelerate the crystallization rate of the perovskite, resulting in high-quality PPF4-based perovskite films with reduced defect density and lower exciton binding energy. Additionally, we incorporated a well-defined fullerene bis-adduct, C60BB, as an interlayer between the perovskite and PCBM layers to optimize energy level alignment. Through the synergistic effects of PPF4 and C60BB, our champion device achieved an efficiency of 16.05 % (certified: 15.86 %), surpassing the 16 % efficiency bottleneck and setting a new benchmark for TPSCs. Moreover, the devices exhibited outstanding stability, retaining 99 % of their initial efficiency after 600 hours of maximum power point tracking under 1 sun condition.