High-quality bulk hybrid perovskite single crystals within minutes by inverse temperature crystallization

Chiral Hybrid Perovskite Single-Crystal Nanowire Arrays for High-Performance Circularly Polarized Light Detection

Circularly polarized light (CPL) detection has emerged as a key technology for various optoelectronics. Chiral hybrid perovskites (CHPs) that combine CPL-sensitive absorption induced by chiral organic ligands and superior photoelectric properties of perovskites are promising candidates for direct CPL detection. To date, most of the CHP detectors are made up of polycrystalline thin-film, which results in a rather limited discrimination of CPL due to the existence of redundant impurities and intrinsic defect states originating from rapid crystallization process. Here, it is developed a direct CPL detector with high photocurrent and polarization selectivity based on low-defect CHP single-crystal nanowire arrays. Large-scale CHP nanowires are obtained through a micropillar template-assisted capillary-bridge rise approach. Thanks to the high crystallinity and ordered crystallographic alignment of these arrays, a CPL photodetector with high light on/off ratio of 1.8 × 104 , excellent responsivity of 1.4 A W-1 , and an outstanding anisotropy factor of 0.24 for photocurrent has been achieved. These results would provide useful enlightenment for direct CPL detection in high-performance chiral optoelectronics.

Origin of phonon-limited mobility in two-dimensional metal dichalcogenides

Metal dichalcogenides are novel two-dimensional (2D) semiconductors after the discovery of graphene. In this article, phonon-limited mobility for six kinds of 2D semiconductors with the composition of MX₂is reviewed, in which M (Cr, Mo and W) is the transition metal, and X (S and Se) is the chalcogen element. The review is divided into three parts. In the first part, we briefly introduce the calculation method of mobility, including the empirical model and Boltzmann transport theory (BTE). The application scope, merits and limitations of these methods are summarized. In the second part, we explore empirical models to calculate the mobility of MX₂, including longitudinal acoustic phonon, optical phonon (OP) and polar optical phonon (POP) models. The contribution of multi-valley to mobility is reviewed in the calculation. The differences between static and high-frequency dielectric constants (Δϵ) are only 0.13 and 0.03 for MoS₂and WS₂. Such a low value indicates that the polarization hardly changes in the external field. So, their mobility is not determined by POP, but by deformation potential models. Different from GaAs, POP scattering plays a decisive role in its mobility. Our investigations also reveal that the scattering from POP cannot be ignored in CrSe₂, MoSe₂and WSe₂. In the third parts, we investigate the mobility of MX₂using electron-phonon coupling matrix element, which is based on BTE from the framework of a many-body quantum-field theory. Valence band splitting of MoS₂and WS₂is induced by spin-orbit coupling effect, which leads to the increase of hole mobility. In particular, we review in detail the theoretical and experimental results of MoS₂mobility in recent ten years, and its mobility is also compared with other materials to deepen the understanding.

Yb2+-Alloyed Cs4PbI6-CsPbI3 Perovskite Nanocomposites for Efficient and Stable Pure-Red Emission

A series of Yb²⁺-alloyed CsPb_1-xYb_xI₃ (x = 0, 0.2, 0.4, 0.6) perovskite nanocrystals (NCs): are synthesized by a modified hot-injection method. Yb²⁺ alloying induced a blue shift of photoluminescence (PL) spectra. In particular, when x = 0.6, the perovskite NCs exhibit pure-red emission with PL centered at 638 nm. Furthermore, the perovskite NCs with pure-red emission exhibit enhanced air and thermal stability, compared to pure CsPbI₃ NCs. The enhanced stability can be assigned to the formation Cs₄PbI₆-CsPbI₃:Yb composites. Charge-carrier dynamics study indicates that the Cs₄PbI₆-CsPbI₃:Yb composites exhibit ultrafast hot-carrier cooling processes, which could break the Auger reheating effect. These properties suggest the Yb²⁺ alloyed CsPbI₃ perovskite NCs have great potential for high-performance pure-red light-emitting diodes.

Quasi-Zero Dimensional Halide Perovskite Derivates: Synthesis, Status, and Opportunity

In recent decades, many technological advances have been enabled by nanoscale phenomena, giving rise to the field of nanotechnology. In particular, unique optical and electronic phenomena occur on length scales less than 10 nanometres, which enable novel applications. Halide perovskites have been the focus of intense research on their optoelectronic properties and have demonstrated impressive performance in photovoltaic devices and later in other optoelectronic technologies, such as lasers and light-emitting diodes. The most studied crystalline form is the three-dimensional one, but, recently, the exploration of the low-dimensional derivatives has enabled new sub-classes of halide perovskite materials to emerge with distinct properties. In these materials, low-dimensional metal halide structures responsible for the electronic properties are separated and partially insulated from one another by the (typically organic) cations. Confinement occurs on a crystal lattice level, enabling bulk or thin-film materials that retain a degree of low-dimensional character. In particular, quasi-zero dimensional perovskite derivatives are proving to have distinct electronic, absorption, and photoluminescence properties. They are being explored for various technologies beyond photovoltaics (e.g. thermoelectrics, lasing, photodetectors, memristors, capacitors, LEDs). This review brings together the recent literature on these zero-dimensional materials in an interdisciplinary way that can spur applications for these compounds. The synthesis methods, the electrical, optical, and chemical properties, the advances in applications, and the challenges that need to be overcome as candidates for future electronic devices have been covered.

Ternary Hybrid Perovskite Solid Solution Single Crystals: Growth, Composition Determination and Phase Stability in Highly Moist Atmosphere

Ternary hybrid perovskite solid solutions have shown superior optoelectronic properties and better stability than their ABX₃ simple perovskite counterparts under ambient conditions. However, crystal growth and identification of the accurate composition of these complex crystalline compounds remain challenging, and their stability under extreme conditions such as in highly moist atmosphere is unknown. Herein, large-size (up to 2 cm) single crystals of ternary perovskite 0.80FAPbI₃  ⋅ x'FAPbBr₃  ⋅ y'CsPbI₃ (x'+y'=0.20) are grown. An elemental analysis method based on wavelength dispersive X-ray fluorescence is proposed to determine their accurate compositions. Among these single crystals, the composition with y'=0.12 shows the best moisture stability at 90 % relative humidity for 15 days. Other components with richer or poorer Cs⁺ ions undergo different phase segregation behaviours. The performance and stability of photodetectors based on these single crystals are tested. This work offers a deeper insight into phase stability of ternary hybrid perovskite solid solution crystals in highly moist atmosphere.

Sensitive, High-Speed, and Broadband Perovskite Photodetectors with Built-In TiO2 Metalenses

Monolithic integration of nanostructured metalenses with broadband light transmission and good charge transport can simultaneously enhance the sensitivity, speed, and efficiency of photodetectors. The realization of built-in broadband metalenses in perovskite photodetectors, however, has been largely challenged by the limited choice of materials and the difficulty in nanofabrication. Here a new type of broadband-transmitting built-in TiO₂ metalens (meta-TiO₂ ) is devised, which is readily fabricated by one-step and lithograph-free glancing angle deposition. The meta-TiO₂ , which comprises of sub-100 nm TiO₂ nanopillars randomly spaced with a wide range of sub-wavelength distances in 5-200 nm, shows high transmittance of light in the wavelength range of 400-800 nm. The meta-TiO₂ also serves as an efficient electron transporting layer to prevent the exciton recombination and facilitate the photoinduced electron extraction and transport. Replacing the conventional mesoporous TiO₂ with the meta-TiO₂ comprehensively leads to enhancing the detection speed by three orders of magnitude to a few hundred nanoseconds, improving the responsivity and detectivity by one order of magnitude to 0.5 A W^-1 and 10¹³ Jones, respectively, and extending the linear dynamic range by 50% to 120 dB.

Photoinduced Dynamic Defects Responsible for the Giant, Reversible, and Bidirectional Light-Soaking Effect in Perovskite Solar Cells

Perovskite solar cells (PSCs) exhibit large, reversible, and bidirectional light-soaking effects (LSEs); however, these anomalous LSEs are poorly understood, limiting the stability engineering and commercialization. We present a unified defect theory for the LSEs in lead halide perovskites by reconciling their defect photochemistry, ionic migration, and carrier dynamics. We considered typical detrimental defects (I_Pb, I_i, V_I) and observed that two atomic configurations were favored, where the carrier lifetime of one configuration was nearly 1 order of magnitude longer than that in the other. First-principles calculations showed that light illumination promotes ion-diffusion-assisted transitions from energetically stable configurations to metastable configurations, which are converted back to stable configurations in the dark. Fermi-level-dependent formation energies of stable/metastable configurations were used to rationalize contradictory experimental results of anomalous LSEs in PSCs observed in various studies, thus providing insights for minimizing the LSE to achieve high-performance stable PSCs.

Identification of lead vacancy defects in lead halide perovskites

Perovskite photovoltaics advance rapidly, but questions remain regarding point defects: while experiments have detected the presence of electrically active defects no experimentally confirmed microscopic identifications have been reported. Here we identify lead monovacancy (VPb) defects in MAPbI3 (MA = CH3NH3+) using positron annihilation lifetime spectroscopy with the aid of density functional theory. Experiments on thin film and single crystal samples all exhibited dominant positron trapping to lead vacancy defects, and a minimum defect density of ~3 × 1015 cm-3 was determined. There was also evidence of trapping at the vacancy complex [Formula: see text] in a minority of samples, but no trapping to MA-ion vacancies was observed. Our experimental results support the predictions of other first-principles studies that deep level, hole trapping, [Formula: see text], point defects are one of the most stable defects in MAPbI3. This direct detection and identification of a deep level native defect in a halide perovskite, at technologically relevant concentrations, will enable further investigation of defect driven mechanisms.

DC bias electric field effects on ac electrical conductivity of MAPbI3suggesting intrinsic changes on structure and charge carrier dynamics

Methylammonium lead iodide (MAPbI₃) emerges as a promising halide perovskite material for the next generation of solar cells due to its high efficiency and flexibility in material growth. Despite intensive studies of their optical and electronic properties in the past ten years, there are no reports on dc bias electric field effects on conductivity in a wide temperature range. In this work, we report the combined effects of frequency, temperature, and dc bias electric field on the ac conductivity of MAPbI₃. We found that the results of dc bias electric fields are very contrasting in the tetragonal and cubic phases. In the tetragonal phase, sufficiently high dc bias electric fields induce a conductivity peak appearance ∼290 K well evidenced at frequencies higher than 100 kHz. Excluding possible degradation and extrinsic factors, we propose that this peak suggests a ferroelectric-like transition. In the absence of a dc bias electric field, the ac conductivity in the tetragonal phase increases with temperature while decreases with temperature in the cubic phase. Also, ac activation energies for tetragonal and cubic phases were found to be inversely and directly proportional to the dc bias electric field, respectively. This behavior was attributed to the ionic conduction, possibly of MA⁺and I^-ions, for the tetragonal phase. As for the cubic phase, the ac conduction dynamics appear to be metallic-like, which seems to change to a polaronic-controlled charge transport to increased dc bias electric fields.

Magnetic optical rotary dispersion and magnetic circular dichroism in methylammonium lead halide perovskites

Large magnetic optical rotary dispersion (Faraday rotation) has been demonstrated recently in methylammonium lead bromide. Here, we investigate the prospect of extending the active spectral range by altering the halogen. We also investigate the origins of large Faraday rotation in these diamagnetic materials using magnetic circular dichroism (MCD) spectroscopy and the Kramers-Kronig relations. We find that, while MAPbCl₃ (MA = methylammonium) single crystals exhibit a large Verdet constant in the blue, no appreciable Faraday rotation is observed in the red/near infra-red for MAPbI₃ single crystals. However, in all film samples, we find clear evidence of large MCD resulting from the Zeeman splitting of the highly resonant 1s exciton state. Our Kramers-Kronig calculations of Faraday rotation based on MCD data matches well with the dispersion of our experimental data for MAPbCl₃ and MAPbBr₃ , with some deviation in magnitude-demonstrating the excitonic nature of Faraday rotation in these materials. However, our calculations predict significant Faraday rotation in MAPbI₃ , contrary to our experimental results, indicating a potential discrepancy between the properties of the thin film and single crystal.

Solution Epitaxy of Halide Perovskite Thin Single Crystals for Stable Transistors

Halide perovskites hold promise for energy and optoelectronic applications due to their fascinating photophysical properties and facile processing. Among various forms, epitaxial thin single crystals (TSCs) are highly desirable due to their high crystallinity, reduced defects, and easy epitaxial integration with other materials. However, a cost-effective method for obtaining TSCs with perfect epitaxial features remains elusive. Here, we demonstrate a direct epitaxial growth of high-quality all-inorganic perovskite CsPbBr₃ TSCs on various substrates through a facile solution process under near-ambient conditions. Structural characterizations reveal a high-quality epitaxy between the obtained perovskite TSCs and substrates, thus leading to efficiently reduced defects. The resultant TSCs display a low trap density (∼10¹¹ cm^-3) and a long carrier lifetime (∼10.16 ns). Top-gate/top-contact transistors based on these TSCs exhibit high on/off ratios of over 10⁵, an optimal hole mobility of 3.9 cm² V^-1 s^-1, almost hysteresis-free operation, and high stability at room temperature. Such a facile approach for the high-yield production of perovskite epitaxial TSCs will enable a broad range of high-performance electronic applications.

Surface Stabilization of a Formamidinium Perovskite Solar Cell Using Quaternary Ammonium Salt

Dimensionality engineering is an effective approach to improve the stability and power conversion efficiency (PCE) of perovskite solar cells (PSCs). A two-dimensional (2D) perovskite assembled from bulky organic cations to cover the surface of three-dimensional (3D) perovskite can repel ambient moisture and suppress ion migration across the perovskite film. This work demonstrates how the thermal stability of the bulky organic cation of a 2D perovskite affects the crystallinity of the perovskite and the optoelectrical properties of perovskite solar cells. Structural analysis of (FAPbI₃)_0.95(MAPbBr₃)_0.05 (FA = formamidinium ion, MA = methylammonium ion) mixed with a series of bulky cations shows a clear correlation between the structure of the bulky cations and the formation of surface defects in the resultant perovskite films. An organic cation with primary ammonium structure is vulnerable to a deprotonation reaction under typical perovskite-film processing conditions. Decomposition of the bulky cations results in structural defects such as iodide vacancies and metallic lead clusters at the surface of the perovskite film; these defects lead to a nonradiative recombination loss of charge carriers and to severe ion migration during operation of the device. In contrast, a bulky organic cation with a quaternary ammonium structure exhibits superior thermal stability and results in substantially fewer structural defects at the surface of the perovskite film. As a result, the corresponding PSC exhibits the PCE of 21.6% in a reverse current-voltage scan and a stabilized PCE of 20.1% with an excellent lifetime exceeding 1000 h for the encapsulated device under continuous illumination.

High-Performance Perovskite Betavoltaics Employing High-Crystallinity MAPbBr3 Films

Long-life and self-powered betavoltaic batteries are extremely attractive for many fields that require a long-term power supply, such as space exploration, polar exploration, and implantable medical technology. Organic lead halide perovskites are great potential candidate materials for betavoltaic batteries due to the large attenuation coefficient and the long carrier diffusion length, which guarantee the scale match between the penetration depth of β particles and the carrier diffusion length. However, the performance of perovskite betavoltaics is limited by the fabrication process of the thick and high-crystallinity perovskite film. In this work, we demonstrated high-performance perovskite betavoltaic cells using thick, high-quality, and wide-band-gap MAPbBr₃ polycrystalline films. The solvent annealing method was adopted to improve the crystallinity and eliminate the pinholes in the MAPbBr₃ film. The optimal MAPbBr₃ betavoltaic cell achieved a power conversion efficiency (PCE) of 5.35% and a maximum output power of 1.203 μW under radiation of electrons of 15 keV with an equivalent activity of 253 mCi. These results are a nearly 50% improvement from previous reports. Effects of the MAPbBr₃ perovskite layer thickness on the device performance were also discussed. The mechanisms of film-growth processes and device physics could provide insights for the research community of perovskites and betavoltaics.

Creating a Dual-Functional 2D Perovskite Layer at the Interface to Enhance the Performance of Flexible Perovskite Solar Cells

Flexible perovskite solar cells (f-PSCs) have been attracting tremendous attention due to their potentially commercial prospects in flexible energy system and mobile energy system. Reducing the energy barriers and charge extraction losses at the interfaces between perovskite and charge transport layers is essential to improve both efficiency and stability of f-PSCs. Herein, 4-trifluoromethylphenylethylamine iodide (CF₃ PEAI) is introduced to form a 2D perovskite at the interface between perovskite and hole transport layer (HTL). It is found that the 2D perovskite plays a dual-functional role in aligning energy band between perovskite and HTL and passivating the traps in the 3D perovskite, thus reducing energy loss and charge carrier recombination at the interface, facilitating the hole transfer from perovskite to the Spiro-OMeTAD. Consequently, the photovoltaic performance of f-PSCs is significantly improved, leading to a power conversion efficiency (PCE) of 21.1% and a certified PCE of 20.5%. Furthermore, the long-term stability of f-PSCs is greatly improved through the protection of 2D perovskite layer to the underlying 3D perovskite. This work provides an excellent strategy to produce efficient and stable f-PSCs, which will accelerate their potential applications.

Tetragonal-Cubic Phase Transition and Low-Field Dielectric Properties of CH3NH3PbI3 Crystals

The frequency and temperature dependence of dielectric properties of CH₃NH₃PbI₃ (MAPI) crystals have been studied and analyzed in connection with temperature-dependent structural studies. The obtained results bring arguments for the existence of ferroelectricity and aim to complete the current knowledge on the thermally activated conduction mechanisms, in dark equilibrium and in the presence of a small external a.c. electric field. The study correlates the frequency-dispersive dielectric spectra with the conduction mechanisms and their relaxation processes, as well as with the different transport regimes indicated by the Nyquist plots. The different energy barriers revealed by the impedance spectroscopy highlight the dominant transport mechanisms in different frequency and temperature ranges, being associated with the bulk of the grains, their boundaries, and/or the electrodes' interfaces.

Oriented Halide Perovskite Nanostructures and Thin Films for Optoelectronics

Oriented semiconductor nanostructures and thin films exhibit many advantageous properties, such as directional exciton transport, efficient charge transfer and separation, and optical anisotropy, and hence these nanostructures are highly promising for use in optoelectronics and photonics. The controlled growth of these structures can facilitate device integration to improve optoelectronic performance and benefit in-depth fundamental studies of the physical properties of these materials. Halide perovskites have emerged as a new family of promising and cost-effective semiconductor materials for next-generation high-power conversion efficiency photovoltaics and for versatile high-performance optoelectronics, such as light-emitting diodes, lasers, photodetectors, and high-energy radiation imaging and detectors. In this Review, we summarize the advances in the fabrication of halide perovskite nanostructures and thin films with controlled dimensionality and crystallographic orientation, along with their applications and performance characteristics in optoelectronics. We examine the growth methods, mechanisms, and fabrication strategies for several technologically relevant structures, including nanowires, nanoplates, nanostructure arrays, single-crystal thin films, and highly oriented thin films. We highlight and discuss the advantageous photophysical properties and remarkable performance characteristics of oriented nanostructures and thin films for optoelectronics. Finally, we survey the remaining challenges and provide a perspective regarding the opportunities for further progress in this field.

Recent Progress of Chiral Perovskites: Materials, Synthesis, and Properties

Chiral materials with intrinsic inversion-symmetric structures possess many unique physicochemical features, including circular dichroism, circularly polarized photoluminescence, nonlinear optics, ferroelectricity, and spintronics. Halide perovskites have attracted considerable attention owing to their excellent optical and electrical properties, which are particularly suitable for realizing high power-conversion efficiency in solar cells. Recent studies have shown that chirality can be transferred from chiral organic ligands into halide perovskites and the resultant chiral perovskites combine the advantages of both chiral materials and halide perovskites; this provides an ideal platform to design next-generation optoelectronic and spintronic devices. In this progress report, the most recent advances are summarized in various chemical structures of chiral perovskites, their synthesis strategies, chirality generation mechanisms, and physical properties. Furthermore, the potential chiral-halide-perovskite-based applications are presented and the challenges and prospects of chiral perovskites are discussed. This report outlines the diverse construction strategies of and proposes research directions for chiral halide perovskites; thus, it provides insights into the design of novel chiral perovskites and facilitates investigation of the optoelectronic applications that employ chirality.

Managing Defects Density and Interfacial Strain via Underlayer Engineering for Inverted CsPbI2 Br Perovskite Solar Cells with All-Layer Dopant-Free

Inorganic perovskite CsPbI₂ Br has advantages of excellent thermal stability and reasonable bandgap, which make it suitable for top layer of tandem solar cells. Nevertheless, solution-processed all-inorganic perovskites generally suffer from high-density defects as well as significant tensile strain near underlayer/perovskite interface, both leading to compromised device efficiency and stability. In this work, the defect density as well as interfacial tensile strain in inverted CsPbI₂ Br perovskite solar cells (PeSCs) is remarkably reduced by using a bilayer underlayer composed of dopant-free 2,2',7,7'-tetrakis(N,N-dip-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD) and copper phthalocyanine 3,4',4″,4'″-tetrasulfonated acid tetrasodium salt (TS-CuPc) nanoparticles. As compared to control devices with pristine Spiro-OMeTAD, devices based on Spiro-OMeTAD/TS-CuPc exhibit remarkably improved photovoltaic performance and enhanced thermal/humidity stability due to the better perovskite crystallization, improved interfacial passivation, and hole-collection as well as efficient interfacial strain release. As a result, a champion efficiency of 14.85% can be achieved, which is approaching to the best reported for dopant-free and inverted all-inorganic PeSCs. The work thus provides an efficient strategy to simultaneously regulate the defects density and strain issue related to inorganic perovskites.

Variational hysteresis and photoresponse behavior of MAPbX3(X= I, Br, Cl) perovskite single crystals

High-quality MAPbX₃(X= I, Br, Cl) single crystals with a desirable size were grown through an inverse temperature crystallization method. Systematically measurements of current-voltage (I-V) hysteresis show that the hysteresis is strongly dependent on the measuring protocol, including scan rate and light illumination condition, which reveals the competition of three main factors that influence the charge dynamics in different regimes, defect trap, MA⁺dipoles rotation, and ion migration. In the dark, defect trapping is the dominant charge transport dynamics at low bias in the MAPbI₃, while the MA⁺dipole rotation is significant in MAPbBr₃, and ion migration occurs in MAPbCl₃. However, as bias increases, MA⁺dipole rotation plays a crucial role in the conductivity either in the dark or under light illumination. The time-dependent photoresponse exhibits different tendencies under various biases. The slow rising dynamics of photoresponse in MAPbX₃is attributed to the slow rotation of MA⁺dipoles, while an immediate overshoot followed by a decay suggests significant ion migration contribution at high external bias. The results serve as comprehensive experimental support to understand the hysteresis behaviors and slow photoresponse in MAPbX₃, particularly in MAPbCl₃, and provide a guide for future work in MAPbX₃based optoelectronic devices.

Halide Perovskites: A New Era of Solution-Processed Electronics

Organic-inorganic mixed halide perovskites have emerged as an excellent class of materials with a unique combination of optoelectronic properties, suitable for a plethora of applications ranging from solar cells to light-emitting diodes and photoelectrochemical devices. Recent works have showcased hybrid perovskites for electronic applications through improvements in materials design, processing, and device stability. Herein, a comprehensive up-to-date review is presented on hybrid perovskite electronics with a focus on transistors and memories. These applications are supported by the fundamental material properties of hybrid perovskite semiconductors such as tunable bandgap, ambipolar charge transport, reasonable mobility, defect characteristics, and solution processability, which are highlighted first. Then, recent progresses on perovskite-based transistors are reviewed, covering aspects of fabrication process, patterning techniques, contact engineering, 2D versus 3D material selection, and device performance. Furthermore, applications of perovskites in nonvolatile memories and artificial synaptic devices are presented. The ambient instability of hybrid perovskites and the strategies to tackle this bottleneck are also discussed. Finally, an outlook and opportunities to develop perovskite-based electronics as a competitive and feasible technology are highlighted.

Phonon-Limited Mobility and Electron-Phonon Coupling in Lead-Free Halide Double Perovskites

Lead-free halide double perovskites have attracted considerable attention as complements to lead-based halide perovskites in a range of optoelectronic applications. Experiments on Cs₂AgBiBr₆ indicate carrier mobilities in the range of 0.3-11 cm²/(V s) at room temperature, considerably lower than in lead-based perovskites. The origin of low mobilities is currently unclear, calling for an atomic-scale investigation. We report state-of-the-art ab initio calculations of the phonon-limited mobility of charge carriers in lead-free halide double perovskites Cs₂AgBiX₆ (X = Br, Cl). For Cs₂AgBiBr₆, we obtain room-temperature electron and hole mobilities of 17 and 14 cm²/(V s), respectively, in line with experiments. We demonstrate that the cause for the lower mobility of this compound, compared to CH₃NH₃PbI₃, resides in the heavier carrier effective masses. A mode-resolved analysis of scattering rates reveals the predominance of Fröhlich electron-phonon scattering, similar to lead-based perovskites. Our results indicate that, to increase the mobility of lead-free perovskites, it is necessary to reduce the effective masses, for example by cation engineering.

High-Temperature Stable FAPbBr3 Single Crystals for Sensitive X-ray and Visible Light Detection toward Space

Organolead trihalide perovskite single crystals (SCs) offer unprecedented opportunity for X-ray and visible light detection. Nevertheless, it remains a challenge to keep simultaneous high-performance and stability at a high-temperature working mode. Herein, formamidinium lead bromide (FAPbBr₃) SCs are developed to successfully address these issues. Low-temperature crystallized induced FAPbBr₃ SCs possess an excellent mobility-lifetime product and an ultralow surface charge recombination velocity, thus exhibiting an X-ray dose rate as low as 0.3 μGy_air s^-1 as a sensitive radiation detector. Furthermore, it also contributes a specific detectivity as high as 3.5 × 10¹² cm Hz^1/2 W^-1, keeping stable at high-temperature of 460 K as a photodetector. A prototype of an imaging system with diffuse reflection mode is constructed using detectors as receivers, enabling defined scanning images in a high temperature environment. The bifunctional FAPbBr₃ SC detectors will motivate new strategies for stable detection in an extreme space environment.

High speed growth of MAPbBr3 single crystals via low-temperature inverting solubility: enhancement of mobility and trap density for photodetector applications

There has been growing interest in organic-inorganic hybrid perovskites as a promising candidate for optoelectronic applications due to their superior physical properties. Despite this, most of the reported perovskite devices based on polycrystalline thin films suffer immensely from poor stability and high trap density owing to grain boundaries limiting their performance. Perovskite single crystal structures have been recently explored to construct stable devices and reduce the trap density compared to their thin-film counterparts. We present a novel method of growing sizable CH₃NH₃PbBr₃ single crystals based on the high solubility characteristic of hybrid perovskites at low temperatures within inverse temperature crystallization. We compared both the crystallinity of perovskite single crystal structures and optoelectronic charge transport of single crystal photodetectors as a function of dissolution temperature. The performance of the photodetector fabricated with our large-scaled single crystal with high quality demonstrated low trap density, high mobility, and high photoresponse.

Recent Advances in Perovskite Photodetectors for Image Sensing

In recent years, metal halide perovskites have been widely investigated to fabricate photodetectors for image sensing due to the excellent photoelectric performance, tunable bandgap, and low-cost solution preparation process. In this review, a comprehensive overview of the recent advances in perovskite photodetectors for image sensing is provided. First, the key performance parameters and the basic device types of photodetectors are briefly introduced. Then, the recent developments of image sensors on the basis of different dimensional perovskite materials, including 0D, 1D, 2D, and 3D perovskite materials, are highlighted. Besides the device structures and photoelectric properties of perovskite image sensors, the preparation methods of perovskite photodetector arrays are also analyzed. Subsequently, the single-pixel imaging of perovskite photodetectors and the strategies to fabricate narrowband perovskite photodetectors for color discrimination are discussed. Finally, the potential challenges and possible solutions for the future development of perovskite image sensors are presented.

Enhanced Third Harmonic Generation in Lead Bromide Perovskites with Ruddlesden-Popper Planar Faults

Lead halide perovskites provide a test bed for exploring nonlinear optical properties. Although the underlying centrosymmetric crystal structure of 3D lead halide perovskites precludes the phenomenon of second harmonic generation, the third and higher-order harmonic generation are allowed. In this work, we probe the third harmonic generation (THG) from CsPbBr₃ nanocrystals (NCs) and compare it to the THG from CsPbBr₃ NCs with Ruddlesden-Popper planar faults (RP-CsPbBr₃), formed via postsynthetic fusion-growth. The THG from CsPbBr₃ NCs is negligible compared with that of RP-CsPbBr₃ NCs within a wide range of femtosecond excitation wavelengths. We further compare the THG from a thin film of RP-CsPbBr₃ with that of a single crystal of methylammonium lead bromide (MAPbBr₃). The THG efficiency of RP-CsPbBr₃ is found to be three times greater than that of MAPbBr₃. An effective third-order susceptibility of the order of 10^-18 m² V^-2 is obtained for a RP-CsPbBr₃ film, opening up the prospect of inorganic halide perovskite NCs with planar defects for a range of nonlinear optical applications.

Synergetic surface charge transfer doping and passivation toward high efficient and stable perovskite solar cells

Organic-inorganic lead halide perovskite solar cells (PSCs) have received much attention in the last few years due to the high power conversion efficiency (PCE). Generally, perovskite/charge transport layer interface and the defects at the surface and grain boundaries of perovskite film are important factors for the efficiency and stability of PSCs. Herein, we employ an extended benzopentafulvalenes compound (FDC-2-5Cl) with electron-withdrawing pentachlorophenyl group and favorable energy level as charge transfer molecule to treat the perovskite surface. The FDC-2-5Cl with pentachlorophenyl group could accept the electrons from perovskite as a p-type dopant, and passivate the surface defects. The p-type doping effect of FDC-2-5Cl on perovskite surface induced band bending at perovskite surface, which improves the hole extraction from perovskite. As a result, the PSC with FDC-2-5Cl treatment achieves a PCE of 21.16% with an enhanced open-circuit voltage (V oc) of 1.14 V and outstanding long-term stability.

Perovskite random lasers: a tunable coherent light source for emerging applications

Metal halide perovskites have attracted increasing attention due to their superior optical and electrical characteristics, flexible tunability, and easy fabrication processes. Apart from their unprecedented successes in photovoltaic devices, lasing action is the latest exploitation of the optoelectronic performance of perovskites. Among the substantial body of research on the configuration design and light emission quality of perovskite lasers, the random laser is a very interesting stimulated emission phenomenon with unique optical characteristics. In this review article, we first comprehensively overview the development of perovskite-based optoelectronic devices and then focus our discussion on random lasing performance. After an introduction to the historical development of versatile random lasers and perovskite random lasers, we summarize several synthesis methods and discuss their material configurations and stability in synthesized perovskite materials. Following this, a theoretical approach is provided to explain the random lasing mechanism in metal halide perovskites. Finally, we propose future applications of perovskite random lasers, presenting conclusions as well as future challenges, such as quality stability and toxicity reduction, of perovskite materials with regard to practical applications in this promising field.

Tailored conductive fullerenes-based passivator for efficient and stable inverted perovskite solar cells

Interfacial defects result in a limitation to the development of highly efficient and stable perovskite solar cells. The passivation of these defects by adopting various interfacial defects passivation agents is a common method for boosting device performance. However, most existing interfacial defects passivation agents form poorly conductive aggregates at the perovskite interface with the electron transport layer (ETL), hindering the transport of charge carriers. In addition, the electron mobility of passivation agents is an important factor that affects the electron communication between the adjacent layers. Herein, a fullerene-based molecular passivator, [60]fullerene-4-(1-(4-(tert-butyl)phenyl)pyrrolidin-2-yl)benzenaminium (C₆₀-tBu-I), is designed and synthesized. This novel n-doping fullerene ammonium iodide is developed as an interfacial modification agent to accelerate charge transport from the perovskite active layer into the ETL while hindering the nonradiative charge carrier recombination. Hence, compared with the control devices (15.66%), C₆₀-tBu-I-modified device presents a higher efficiency of 17.75%. More importantly, the tert-butyl group dramatically enhances the resistance of perovskite films to water molecular. As a result, C₆₀-tBu-I-modified devices exhibit excellent long-term stability, remaining at more than 87% of the initial power conversion efficiency value after storage for 500 h.

Limits to Electrical Mobility in Lead-Halide Perovskite Semiconductors

Semiconducting polycrystalline thin films are cheap to produce and can be deposited on flexible substrates, yet high-performance electronic devices usually utilize single-crystal semiconductors, owing to their superior charge-carrier mobilities and longer diffusion lengths. Here we show that the electrical performance of polycrystalline films of metal-halide perovskites (MHPs) approaches that of single crystals at room temperature. Combining temperature-dependent terahertz conductivity measurements and ab initio calculations we uncover a complete picture of the origins of charge-carrier scattering in single crystals and polycrystalline films of CH₃NH₃PbI₃. We show that Fröhlich scattering of charge carriers with multiple phonon modes is the dominant mechanism limiting mobility, with grain-boundary scattering further reducing mobility in polycrystalline films. We reconcile the large discrepancy in charge-carrier diffusion lengths between single crystals and films by considering photon reabsorption. Thus, polycrystalline films of MHPs offer great promise for devices beyond solar cells, including light-emitting diodes and modulators.

Study on Performance Improvements in Perovskite-Based Ultraviolet Sensors Prepared Using Toluene Antisolvent and CH3NH3Cl

In this study, a simply structured perovskite-based ultraviolet C (UVC) sensor was prepared using a one-step, low-temperature solution-processing coating method. The UVC sensor utilized CH3NH3PbBr3 perovskite as the light-absorbing layer. To improve the characteristics of CH3NH3PbBr3, an antisolvent process using toluene and the addition of CH3NH3Cl were introduced. The device with these modifications exhibited a response rise/fall time of 15.8/16.2 ms, mobility of 158.7 cm2/V·s, responsivity of 4.57 mA/W, detectivity of 1.02 × 1013 Jones, and external quantum efficiency of 22.32% under the 254-nm UV illumination. Therefore, this methodology could be a good approach in facilitating UVC detection.

Solution-Grown Formamidinium Hybrid Perovskite (FAPbBr3) Single Crystals for α-Particle and γ-Ray Detection at Room Temperature

Compared with the widely reported MAPbBr₃ single crystals, formamidinium-based (FA-based) hybrid perovskites FAPbBr₃ (FPB) with superior chemical and structure stability are expected to be more efficient and perform as more reliable radiation detectors at room temperature. Here, we employ an improved inverse temperature crystallization method to grow FPB bulk single crystals, where issues associated with the retrograde solubility behavior are resolved. A crystal growth phase diagram has been proposed, and accordingly, growth parameters are optimized to avoid the formation of NH₄Pb₂Br₅ secondary phase. The resulting FPB crystals exhibit a high resistivity of 2.8 × 10⁹ Ω·cm and high electron and hole mobility-lifetime products (μτ) of 8.0 × 10^-4 and 1.1 × 10^-3 cm²·V^-1, respectively. Simultaneously, the electron and hole mobilities (μ) are evaluated to be 22.2 and 66.1 cm²·V^-1·s^-1, respectively, based on the time-of-flight technique. Furthermore, a Au/FPB SC/Au detector is constructed that demonstrates a resolvable gamma peak from 59.5 keV ²⁴¹Am γ-rays at room temperature for the first time. An energy resolution of 40.1% is obtained at 30 V by collecting the hole signals. These results demonstrate the great potential of FAPbBr₃ as a hybrid material for γ-ray spectroscopy and imaging.

A polymer controlled nucleation route towards the generalized growth of organic-inorganic perovskite single crystals

Recently, there are significant progresses in the growth of organic-inorganic lead halide perovskite single crystals, however, due to their susceptible nucleation and growth mechanisms and solvent requirements, the efficient and generalized growth for these single crystals is still challenging. Here we report the work towards this target with a polymer-controlled nucleation process for the highly efficient growth of large-size high-quality simple ternary, mixed-cations and mixed-halide perovskite single crystals. Among them, the carrier lifetime of FAPbBr₃ single crystals is largely improved to 10199 ns. Mixed MA/FAPbBr₃ single crystals are synthesized. The crucial point in this process is suggested to be an appropriate coordinative interaction between polymer oxygen groups and Pb²⁺, greatly decreasing the nuclei concentrations by as much as 4 orders of magnitudes. This polymer-controlled route would help optimizing the solution-based OIHPs crystal growth and promoting applications of perovskite single crystals.

Research into single crystal organic-inorganic halide perovskites have gained momentum due to the potential applications, yet the growth is still a challenge. Here, the authors demonstrate a universal method based on polymer controlled nucleation process to achieve large-size and high-quality perovskite single crystals.

2D materials for conducting holes from grain boundaries in perovskite solar cells

Grain boundaries in organic-inorganic halide perovskite solar cells (PSCs) have been found to be detrimental to the photovoltaic performance of devices. Here, we develop a unique approach to overcome this problem by modifying the edges of perovskite grain boundaries with flakes of high-mobility two-dimensional (2D) materials via a convenient solution process. A synergistic effect between the 2D flakes and perovskite grain boundaries is observed for the first time, which can significantly enhance the performance of PSCs. We find that the 2D flakes can conduct holes from the grain boundaries to the hole transport layers in PSCs, thereby making hole channels in the grain boundaries of the devices. Hence, 2D flakes with high carrier mobilities and short distances to grain boundaries can induce a more pronounced performance enhancement of the devices. This work presents a cost-effective strategy for improving the performance of PSCs by using high-mobility 2D materials.

Bismuth Doping Alters Structural Phase Transitions in Methylammonium Lead Tribromide Single Crystals

We study the effects of bismuth doping on the crystal structure and phase transitions in single crystals of the perovskite semiconductor methylammonium lead tribromide, MAPbBr₃. By measuring the temperature-dependent specific heat capacity (C_p), we find that as the Bi doping increases, the phase transition assigned to the cubic to tetragonal phase boundary decreases in temperature. Furthermore, after doping we observe one phase transition between 135 and 155 K, in contrast to two transitions observed in the undoped single crystal. These results appear strikingly similar to previously reported effects of mechanical pressure on perovskite crystal structure. Using X-ray diffraction, we show that the lattice constant decreases as Bi is incorporated into the crystal, as predicted by density functional theory. We propose that bismuth substitutional doping on the lead site is dominant, resulting in Bi_Pb⁺ centers that induce compressive chemical strain that alters the crystalline phase transitions.

Ligand assisted growth of perovskite single crystals with low defect density

A low defect density in metal halide perovskite single crystals is critical to achieve high performance optoelectronic devices. Here we show the reduction of defect density in perovskite single crystals grown by a ligand-assisted solution process with 3‐(decyldimethylammonio)‐propane‐sulfonate inner salt (DPSI) as an additive. DPSI ligands anchoring with lead ions on perovskite crystal surfaces not only suppress nucleation in solution, but also regulate the addition of proper ions to the growing surface, which greatly enhances the crystal quality. The grown CH₃NH₃PbI₃ crystals show better crystallinity and a 23-fold smaller trap density of 7 × 10¹⁰ cm⁻³ than the optimized control crystals. The enhanced material properties result in significantly suppressed ion migration and superior X-ray detection sensitivity of CH₃NH₃PbI₃ detectors of (2.6 ± 0.4) × 10⁶ µC Gy⁻¹air cm⁻² for 60 kVp X-ray and the lowest detectable dose rate reaches (5.0 ± 0.7) nGy s⁻¹, which enables reduced radiation dose to patients in medical X-ray diagnostics.

The performance of a metal halide perovskite single crystal is governed by the defect density. Here, the authors report a high quality single crystal perovskite grown by a ligand-assisted solution process with DPSI achieving 23-fold smaller trap density than that without DPSI.

Revealing Charge Carrier Mobility and Defect Densities in Metal Halide Perovskites via Space-Charge-Limited Current Measurements

Space-charge-limited current (SCLC) measurements have been widely used to study the charge carrier mobility and trap density in semiconductors. However, their applicability to metal halide perovskites is not straightforward, due to the mixed ionic and electronic nature of these materials. Here, we discuss the pitfalls of SCLC for perovskite semiconductors, and especially the effect of mobile ions. We show, using drift-diffusion (DD) simulations, that the ions strongly affect the measurement and that the usual analysis and interpretation of SCLC need to be refined. We highlight that the trap density and mobility cannot be directly quantified using classical methods. We discuss the advantages of pulsed SCLC for obtaining reliable data with minimal influence of the ionic motion. We then show that fitting the pulsed SCLC with DD modeling is a reliable method for extracting mobility, trap, and ion densities simultaneously. As a proof of concept, we obtain a trap density of 1.3 × 10¹³ cm^-3, an ion density of 1.1 × 10¹³ cm^-3, and a mobility of 13 cm² V^-1 s^-1 for a MAPbBr₃ single crystal.

Revealing Charge Carrier Mobility and Defect Densities in Metal Halide Perovskites via Space-Charge-Limited Current Measurements

Space-charge-limited current (SCLC) measurements have been widely used to study the charge carrier mobility and trap density in semiconductors. However, their applicability to metal halide perovskites is not straightforward, due to the mixed ionic and electronic nature of these materials. Here, we discuss the pitfalls of SCLC for perovskite semiconductors, and especially the effect of mobile ions. We show, using drift-diffusion (DD) simulations, that the ions strongly affect the measurement and that the usual analysis and interpretation of SCLC need to be refined. We highlight that the trap density and mobility cannot be directly quantified using classical methods. We discuss the advantages of pulsed SCLC for obtaining reliable data with minimal influence of the ionic motion. We then show that fitting the pulsed SCLC with DD modeling is a reliable method for extracting mobility, trap, and ion densities simultaneously. As a proof of concept, we obtain a trap density of 1.3 × 1013 cm-3, an ion density of 1.1 × 1013 cm-3, and a mobility of 13 cm2 V-1 s-1 for a MAPbBr3 single crystal.

Gentle Materials Need Gentle Fabrication: Encapsulation of Perovskites by Gas-Phase Alumina Deposition

Metal halide perovskites have attracted tremendous attention as promising materials for future-generation optoelectronic devices. Despite their outstanding optical and transport properties, the lack of environmental and operational stability remains a major practical challenge. One of the promising stabilization avenues is metal oxide encapsulation via atomic layer deposition (ALD); however, the unavoidable reaction of metal precursors with the perovskite surface in conventional ALD leads to degradation and restructuring of the perovskites' surfaces. This Perspective highlights the development of a modified gas-phase ALD technique for alumina encapsulation that not only prevents perovskites' degradation but also significantly improves their optical properties and air stability. The correlation between precise atomic interactions at the perovskite-metal oxide interface with the dramatically enhanced optical properties is supported by density functional theory calculations, which also underlines the widespread applicability of this gentle technique for a variety of perovskite nanostructures unbarring potential opportunities offered by combination of these approaches.

Ambient-Air-Stable Lead-Free CsSnI3 Solar Cells with Greater than 7.5% Efficiency

Black orthorhombic (B-γ) CsSnI₃ with reduced biotoxicity and environmental impact and excellent optoelectronic properties is being considered as a promising eco-friendly candidate for high-performing perovskite solar cells (PSCs). A major challenge in a large-scale implementation of CsSnI₃ PSCs includes the rapid transformation of Sn²⁺ to Sn⁴⁺ (within a few minutes) under an ambient-air condition. Here, we demonstrate that ambient-air stable B-γ CsSnI₃ PSCs can be fabricated by incorporating N,N'-methylenebis(acrylamide) (MBAA) into the perovskite layer and by using poly(3-hexylthiophene) as the hole transporting material. The lone electron pairs of -NH and -CO units of MBAA are designed to form coordination bonding with Sn²⁺ in the B-γ CsSnI₃, resulting in a reduced defect (Sn⁴⁺) density and better stability under multiple conditions for the perovskite light absorber. After a modification, the highest power conversion efficiency (PCE) of 7.50% is documented under an ambient-air condition for the unencapsulated CsSnI₃-MBAA PSC. Furthermore, the MBAA-modified devices sustain 60.2%, 76.5%, and 58.4% of their initial PCEs after 1440 h of storage in an inert condition, after 120 h of storage in an ambient-air condition, and after 120 h of 1 Sun continuous illumination, respectively.

One-Pot Heterointerfacial Metamorphosis for Synthesis and Control of Widely Varying Heterostructured Nanoparticles

Despite remarkable facileness and potential in forming a wide variety of heterostructured nanoparticles with extraordinary compositional and structural complexity, one-pot synthesis of multicomponent heterostructures is largely limited by the lack of fundamental mechanistic understanding, designing principles, and well-established, generally applicable chemical methods. Herein, we developed a one-pot heterointerfacial metamorphosis (1HIM) method that allows heterointerfaces inside a particle to undergo multiple equilibrium stages to form a variety of highly crystalline heterostructured nanoparticles at a relatively low temperature (<100 °C). As proof-of-concept experiments, it was shown that widely different single-crystalline semiconductor-metal anisotropic nanoparticles with synergistic chemical, spectroscopic, and band-gap-engineering properties, including a series of metal-semiconductor nanoframes with high structural and compositional tunability, can be formed by using the 1HIM approach. 1HIM offers a new paradigm to synthesize previously unobtainable or poorly controllable heterostructures with unique or synergistic properties and functions.

Crystallization of CsPbBr3 single crystals in water for X-ray detection

Metal halide perovskites have fascinated the research community over the past decade, and demonstrated unprecedented success in optoelectronics. In particular, perovskite single crystals have emerged as promising candidates for ionization radiation detection, due to the excellent opto-electronic properties. However, most of the reported crystals are grown in organic solvents and require high temperature. In this work, we develop a low-temperature crystallization strategy to grow CsPbBr₃ perovskite single crystals in water. Then, we carefully investigate the structure and optoelectronic properties of the crystals obtained, and compare them with CsPbBr₃ crystals grown in dimethyl sulfoxide. Interestingly, the water grown crystals exhibit a distinct crystal habit, superior charge transport properties and better stability in air. We also fabricate X-ray detectors based on the CsPbBr₃ crystals, and systematically characterize their device performance. The crystals grown in water demonstrate great potential for X-ray imaging with enhanced performance metrics.

Perovskite single crystals are commonly grown in organic solvents, which require relatively high temperature condition. Here, the authors develop a low-temperature crystallisation strategy to grow CsPbBr₃ single crystals in water with improved charge transport properties and stability.

Facile Fabrication of Self-Assembly Functionalized Polythiophene Hole Transporting Layer for High Performance Perovskite Solar Cells

Crystallinity and crystal orientation have a predominant impact on a materials' semiconducting properties, thus it is essential to manipulate the microstructure arrangements for desired semiconducting device performance. Here, ultra-uniform hole-transporting material (HTM) by self-assembling COOH-functionalized P3HT (P3HT-COOH) is fabricated, on which near single crystal quality perovskite thin film can be grown. In particular, the self-assembly approach facilitates the P3HT-COOH molecules to form an ordered and homogeneous monolayer on top of the indium tin oxide (ITO) electrode facilitate the perovskite crystalline film growth with high quality and preferred orientations. After detailed spectroscopy and device characterizations, it is found that the carboxylic acid anchoring groups can down-shift the work function and passivate the ITO surface, retarding the interface carrier recombination. As a result, the device made with the self-assembled HTM show high open-circuit voltage over 1.10 V and extend the lifetime over 4,300 h when storing at 30% relative humidity. Moreover, the cell works efficiently under much reduced light power, making it useful as power source under dim-light conditions. The demonstration suggests a new facile way of fabricating monolayer HTM for high efficiency perovskite devices, as well as the interconnecting layer needed for tandem cell.

Photophysics of 2D Organic-Inorganic Hybrid Lead Halide Perovskites: Progress, Debates, and Challenges

2D organic-inorganic hybrid Ruddlesden-Popper perovskites (RPPs) have recently attracted increasing attention due to their excellent environmental stability, high degree of electronic tunability, and natural multiquantum-well structures. Although there is a rapid development of photoelectronic applications in solar cells, photodetectors, light emitting diodes (LEDs), and lasers based on 2D RPPs, the state-of-the-art performance is far inferior to that of the existing devices because of the limited understanding on fundamental physics, especially special photophysics in carrier dynamics, excitonic fine structures, excitonic quasiparticles, and spin-related effect. Thus, there is still plenty of room to improve the performances of photoelectronic devices based on 2D RPPs by enhancing knowledge on fundamental photophysics. This review highlights the special photophysics of 2D RPPs that is fundamentally different from the conventional 3D congeners. It also provides the most recent progress, debates, challenges, prospects, and in-depth understanding of photophysics in 2D perovskites, which is significant for not only boosting performance of solar cells, LEDs, photodetectors, but also future development of applications in lasers, spintronics, quantum information, and integrated photonic chips.

Zero-Dimensional Lead-Free FA3Bi2I9 Single Crystals for High-Performance X-ray Detection

Direct X-ray detectors based on metal halide perovskites and their derivatives exhibit high sensitivity and low limit of detection (LoD). Compared with three-dimensional (3D) hybrid lead halide perovskites, low-dimensional A₃Bi₂I₉ perovskite derivatives (A = Cs, Rb, NH₄, CH₃NH₃(MA)) present better stability, greater environmental friendliness, and comparable X-ray detection performance. Here, we report FA₃Bi₂I₉ (FA= CH(NH₂)₂) single crystals (SCs) as a new member of the A₃Bi₂I₉ series for X-ray detection, which were prepared by the nucleation-controlled secondary solution constant temperature evaporation (SSCE) method. Centimeter-sized FA₃Bi₂I₉ SCs show a full width at half-maximum (fwhm) of 0.0096°, which is superior to that of recently reported Cs₃Bi₂I₉ (0.058°) and MA₃Bi₂I₉ SCs (0.024°) obtained by inverse temperature crystallization (ITC). The as-grown FA₃Bi₂I₉ SC shows a large resistivity of 7.8 × 10¹⁰ Ω cm and a high ion migration activation energy (E_a) of 0.56 eV, which can guarantee a low noise level and good operational stability under a large external bias. The FA₃Bi₂I₉ SC detector exhibits a LoD of 0.2 μGy_air s^-1, a sensitivity of 598.1 μC Gy_air ^-1 cm ^-2, and an X-ray detection efficiency of 33.5%, which are much better than those of the commercialized amorphous selenium detector. Results presented here will provide a new lead-free perovskite-type material to achieve green, sensitive, and stable X-ray detectors.