Large Crystalline Grains Research Articles

Quantification of microstructural homogeneity in indium arsenide epilayers by X-ray diffraction

In this article a complete procedure to investigate thin semiconductor plates (epitaxial layers), including high-resolution X-ray diffraction measurements, mathematical modelling of both crystalline structure and crystalline microstructure and computations to approximate solving inverse problems, is proposed and described in detail. The method is successfully applied to estimate crystalline homogeneity of a square indium-arsenide plate epitaxially-grown on gallium-arsenide substrate. To this end, the specimen is tested in nine areas around points forming a square grid. It is demonstrated that whole specimen may be regarded as a single large crystalline grain consisting of crystallites separated by small-angle boundaries. The crystallites occur as rode-like cuboids elongated in the direction perpendicular to the plate surface, with different areas of the sample and with base sizes not much differing. The mean-absolute second-order strain is very small and almost constant in the whole sample. The first-order strain also appears and, effectively, the structure of the crystalline layer is tetragonal with unit-cell parameters being smaller parallelly and larger perpendicularly to the layer surface and varying slightly in the layer. The results are presented in tables and figures and commented.

Defect Passivation and Crystallization Regulation for Efficient and Stable Formamidinium Lead Iodide Solar Cells with Multifunctional Amidino Additive.

Amidino-based additives show great potential in high-performance perovskite solar cells (PSCs). However, the role of different functional groups in amidino-based additives have not been well elucidated. Herein, two multifunctional amidino additives 4-amidinobenzoic acid hydrochloride (ABAc) and 4-amidinobenzamide hydrochloride (ABAm) are employed to improve the film quality of formamidinium lead iodide (FAPbI3) perovskites. Compared with ABAc, the amide group imparts ABAm with larger dipole moment and thus stronger interactions with the perovskite components, i.e., the hydrogen bonds between N…H and I- anion and coordination bonds between C = O and Pb2+ cation. It strengthens the passivation effect of iodine vacancy defect and slows down the crystallization process of α-FAPbI3, resulting in the significantly reduced non-radiative recombination, long carrier lifetime of 1.7 µs, uniformly large crystalline grains, and enhances hydrophobicity. Profiting from the improved film quality, the ABAm-treated PSC achieves a high efficiency of 24.60%, and maintains 93% of the initial efficiency after storage in ambient environment for 1200 hours. This work provides new insights for rational design of multifunctional additives regarding of defect passivation and crystallization control toward highly efficient and stable PSCs.

Flexible Indoor Perovskite Solar Cells by In Situ Bottom-Up Crystallization Modulation and Interfacial Passivation.

A robust perovskite-buried interface is pivotal for achieving high-performance flexible indoor photovoltaics as it significantly influences charge transport and extraction efficiency. Herein, a molecular bridge strategy is introduced utilizing sodium 2-cyanoacetate (SZC) additive at the perovskite-buried interface to simultaneously achieve in situ passivation of interfacial defects and bottom-up crystallization modulation, resulting in high-performance flexible indoor photovoltaic applications. Supported by both theoretical calculations and experimental evidences, it illustrates how SZCs serve as molecular bridges, establishing robust bonds between SnO2 transport layer and perovskite, mitigating oxygen vacancy defects and under-coordinated Pb defects at interface during flexible fabrication. This, in turn, enhances interfacial energy level alignment and facilitates efficient carrier transport. Moreover, this in situ investigation of perovskite crystallization dynamics reveals bottom-up crystallization modulation, extending perovskite growth at the buried interface and influencing subsequent surface recrystallization. This results in larger crystalline grains and improved lattice strain of the perovskite during flexible fabrication. Finally, the optimized flexible solar cells achieve an impressive efficiency exceeding 41% at 1000 lux, with a fill factor as high as 84.32%. The concept of the molecular bridge represents a significant advancement in enhancing the performance of perovskite-based flexible indoor photovoltaics for the upcoming era of Internet of Things (IoT).

Nanocavity-Mediated Purcell Enhancement of Er in TiO2 Thin Films Grown via Atomic Layer Deposition.

The use of trivalent erbium (Er3+), typically embedded as an atomic defect in the solid-state, has widespread adoption as a dopant in telecommunication devices and shows promise as a spin-based quantum memory for quantum communication. In particular, its natural telecom C-band optical transition and spin-photon interface make it an ideal candidate for integration into existing optical fiber networks without the need for quantum frequency conversion. However, successful scaling requires a host material with few intrinsic nuclear spins, compatibility with semiconductor foundry processes, and straightforward integration with silicon photonics. Here, we present Er-doped titanium dioxide (TiO2) thin film growth on silicon substrates using a foundry-scalable atomic layer deposition process with a wide range of doping controls over the Er concentration. Even though the as-grown films are amorphous after oxygen annealing, they exhibit relatively large crystalline grains, and the embedded Er ions exhibit the characteristic optical emission spectrum from anatase TiO2. Critically, this growth and annealing process maintains the low surface roughness required for nanophotonic integration. Finally, we interface Er ensembles with high quality factor Si nanophotonic cavities via evanescent coupling and demonstrate a large Purcell enhancement (≈300) of their optical lifetime. Our findings demonstrate a low-temperature, nondestructive, and substrate-independent process for integrating Er-doped materials with silicon photonics. At high doping densities this platform can enable integrated photonic components such as on-chip amplifiers and lasers, while dilute concentrations can realize single ion quantum memories.

Organic-inorganic hybrid material for hole transport in inverted perovskite solar cells.

Hole mobility is critical to the power conversion efficiencies of perovskite solar cells (PSCs). Organic small-molecule hole-transporting materials (HTMs) have attracted considerable interest in PSCs due to their structural flexibility and operational durability, but they suffer from modest hole mobility. On the other hand, inorganic HTMs with good hole mobility are inflexible in structural variation and exhibit unsatisfactory cell efficiency. In this study, a ligand BT28 and its zinc-based coordination complex BTZ30 were synthesized, characterized, and investigated as HTMs for PSC applications. The mixed-halide perovskites can be grown uniformly with large crystalline grains on both HTMs, which exhibit similar optical and electrochemical properties. However, it was discovered that the BTZ30-based solar cell exhibited an open-circuit voltage of 1.0817 V and a high short-circuit current density of 23.1392 mA cm-2 with a champion power conversion efficiency of close to 20 %. The performance difference between the two HTMs can be attributed to the difference in their hole mobilities, which is 63.31 % higher for BTZ30 than BT28. The comparison of non-metal and metal HTMs revealed the importance of considering hybrid structures to overcome some shortcomings associated with organic and inorganic HTMs and achieve high-performance PSCs.

Crystallization kinetics of Al2O3-28mol%Lu2O3 glass and full crystallized transparent Lu3Al5O12-based nanoceramics

Transparent Lu3Al5O12 (LuAG) ceramics have become very promising phosphor matrix materials due to their high doping concentration and luminous efficiency, thermal conductivity and thermal stability. However, LuAG transparent ceramics prepared by traditional powder sintering method are facing several problems, such as time-consuming and energy-consuming, complex preparation process, high quality of raw material powders and large crystalline grain size. Here we report facile elaboration of transparent LuAG-Al2O3 two-phase nanocrystalline ceramics through pressureless crystallization (1000 °C, 2 h) of 72 mol.% Al2O3-28 mol.% Lu2O3 (ALu28) bulk glasses combined with the crystallization kinetics analysis. The results of the crystallization kinetics analysis show that the ALu28 bulk glasses have a low activation energy (<750 kJ mol−1) and a crystallization mechanism of three-dimensional crystal growth mode accompanied by volume nucleation. The resulting LuAG-Al2O3 ceramics with nanosized grains and dense three-dimensional network nanostructures present good transmittance (80.6 %@780 nm) and excellent mechanical properties (hardness is 24 GPa).

Perovskite solar cell fabrication via scalable thermal‐assisted and meniscus‐guided bar‐coating method in open air

AbstractBackgroundPerovskite‐based solar cell is getting great attention as a promising candidate for future solar cell technology, since high power conversion efficiency above 25.5% have been demonstrated for small scale PSCs from films prepared mainly by spin‐coating method, which is not feasible for large area film preparation. Scalable and cost‐effective film fabrication techniques are urgently needed for the commercialization of perovskite solar cells.ObjectiveTo develop a process from which large‐area, high quality and unifoem perovskite films, as well as the hole‐transporting layer films, can be prepared in a simple and cheap way for the practical application and mass production of perovskite solar cells.MethodsLarge‐area electron‐transporting layer layers of mp‐TiO2 and c‐TiO2 were prepared on the FTO substrate by the solution‐shearing method. Then the 10 × 10 cm2 perovskite film was prepared by using a bar‐coater from perovskite precursor solution in ACN/MA solvent system under optimized conditions. The spiro‐OMeTAD film was also prepared by bar‐coating process. Standard‐sized pieces (1.5 × 1.8 cm2) were cut and the Ag metal electrode (80 nm) was deposited through a shadow mask in a thermal evaporation system for device evaluation.ResultsThe large crystalline grains and pinhole‐free perovskite film obtained were fully characterized to show better film properties compared to that from the spin‐coated film, and appeared less sensitive to moisture. A higher PCE of 19.72% was achieved for standard‐sized devices fabricated from the bar‐coated perovskite film with spiro‐OMeRAD film spin‐coated on top, or an excellent PCE of 18.10% was obtained with bar‐coated spiro‐OMeTAD layer on top.ConclusionsThis work demonstrates that the simple and scalable process of bar‐coating can offer high quality and homogeneous films of perovskite and spiro‐OMeTAD respectively. It is compatible with the R2R process and useful in realizing the commercialization of PSC technology.

Pinhole-free 2D Ruddlesden–Popper perovskite layer with close packed large crystalline grains, suitable for optoelectronic applications

Here, we achieved pinhole-free 2D Ruddlesden–Popper Perovskite (RPP) BA2PbI4 layers with close packed crystalline grains with dimension of about 30 × 30 µm2, which have been demonstrated to be favorable for optoelectronic applications, such as fast response RPP-based metal/semiconductor/metal photodetectors. We explored affecting parameters in hot casting of BA2PbI4 layers, and proved that oxygen plasma treatment prior to hot casting plays a significant role to achieve high quality close packed polycrystalline RPP layers at lower hot cast temperatures. Moreover, we demonstrate that crystal growth of 2D BA2PbI4 can be dominantly controlled by the rate of solvent evaporation through substrate temperature or rotational speed, while molarity of the prepared RPP/DMF precursor is the dominant factor that determines the RPP layer thickness, and can affect the spectral response of the realized photodetector. Benefiting from the high light absorption and inherent chemical stability of 2D RPP layers, we achieved high responsivity and stability, and fast response photodetection from perovskite active layer. We achieved a fast photoresponse with rise and fall times of 189 µs and 300 µs, and the maximum responsivity of 119 mA/W and detectivity of 2.15 × 108 Jones in response to illumination wavelength of 450 nm. The presented polycrystalline RPP-based photodetector benefits from a simple and low-cost fabrication process, suitable for large area production on glass substrate, a good stability and responsivity, and a promising fast photoresponse, even around that of exfoliated single crystal RPP-based counterparts. However, it is well known that exfoliation methods suffer from poor repeatability and scalability, which make them incompatible with mass production and large area applications.

Thermal Stability of Semiconductor Nanocrystal Solids: Understanding Nanocrystal Sintering and Grain Growth

Nanomaterials are naturally metastable with respect to bulk solids. This raises the very important fundamental problem of their morphological stability, especially when nanoscale crystallites are touching or nearly touching each other, such as in thin-film devices. In some cases, nanostructuring must be preserved under operational conditions (e.g., in quantum dot LEDs, lasers, photodetectors, and nanogranular thermoelectric devices). In other cases, we use nanocrystalline particles as precursors to a material with large crystalline grains and aim to sinter them as efficiently as possible (e.g., in polycrystalline thin-film solar cells). We carried out a systematic study of sintering and grain growth in materials composed of various sub-10 nm semiconductor grains. The boundaries between individual semiconductor grains have been chemically engineered using inorganic surface ligands. We found that the early stages of sintering and grain growth of nanocrystalline semiconductors are controlled by the ion mobility at the nanocrystal surfaces, while the late stages of grain growth are controlled by the mobility of the grain boundaries. This appears to be a general phenomenon for semiconductor nanocrystals, and it leads to several interesting and counterintuitive trends. For example, III–V InAs nanocrystals are generally much more resilient against sintering and grain growth compared to II–VI CdSe nanocrystals even though bulk CdSe has significantly higher melting point temperature than InAs (1268 °C vs 942 °C). Grain growth can be dramatically accelerated when coupled to solid−solid phase transitions. These findings expand our toolbox for rational design of nanocrystal materials for different applications.

Enhanced energy conversion performance of silicon solar cells by quantum-confinement effect of polysilicon oxide

We propose a highly transparent polysilicon oxide (poly-SiOx)/crystalline silicon (c-Si) front passivation contact (poly-SiOx/c-Si) to overcome the parasitic current drawback and enhance the stability of silicon heterojunction (SHJ) solar cells. Poly-SiOx has a mixed-phase crystalline structure with large crystalline grains embedded in a wide-gap amorphous silicon oxide (a-SiOx) matrix, resulting in a quantum confinement effect. While the large crystalline phase facilitates dopant activation toward high conductivity (elevated Fermi level), resulting in substantial band bending at the c-Si/poly-SiOx interface for additional field-effect passivation, the a-SiOx matrix allows additional chemical surface passivation. Thus, passivation quality with an implied open-circuit voltage of 732 mV and a recombination current density of 4.3 fA/cm2 was achieved. Owing to the interaction between the quantum confinement effect and the wide-gap a-SiOx phase, the mixed-phase structure had a wide bandgap (1.98 eV), significantly increasing the absorption of the device in the short-wavelength region (≤500 nm). A hybrid rear-emitter SHJ solar cell using poly-SiOx/c-Si achieved an efficiency of 23.95% with Voc = 723 mV, a short-circuit current density of 40.9 mA/cm2, and a fill factor of 81%.

Benzimidazole Based Hole‐Transporting Materials for High‐performance Inverted Perovskite Solar Cells

AbstractInterfaces play a decisive role in perovskite solar cells’ power conversion efficiency and their long‐term durability. Small‐molecule hole‐transporting materials (HTMs) have grabbed enormous attention due to their structural flexibility, material properties, and stabilities, allowing for improved operational durability in perovskite photovoltaics. This study synthesizes and investigates a new class of benzimidazole‐based small molecules, named YJS001 and YJS003, serving as the HTMs to enable high‐efficiency mixed‐cation mixed‐halide perovskite solar cells. The benzimidazole‐based materials are dopant‐free HTMs composed of donor and acceptor building blocks that are designed to engineer the energy level alignment near the HTM/perovskite interface. Mixed‐cation mixed‐halide perovskites can be grown uniformly on both HTMs with large crystalline grains. It is discovered that the donor‐rich YJS003‐based solar cell exhibits a high open‐circuit voltage of 1.09 V with a champion power conversion efficiency of over 20%. Power‐dependent current–voltage characteristics of the solar cells are analyzed, from which the high performance of YJS003's excellent hole mobility and well‐aligned energy level is attributed. This work introduces a new class of benzimidazole‐based small molecules as HTMs, that paves the path for dopant free interface material development for commercialization of perovskite solar cells.

Titania coated silica core-shell spheres with dual grain size as efficient photocatalysts

The TiO2 nanoclusters were modified into the pores of silica core-shell particles (SiO2@dSiO2) by the sol-gel method, and the loading amount reached 47%. Based on the Ostwald ripening theory, by simply extending the reaction time, a part of the TiO2 in the pores of the shell was dissolved and then re-deposited on the outer surface of the shell to form a TiO2 layer. Using this method, TiO2 crystalline grains of different sizes were obtained simultaneously inside and outside the shell of silica core-shell spheres. Small-sized crystalline grains were located in the pores of the shell, and they had a strong quantum size effect. The large crystalline grains were located in the TiO2 layer on the outer surface of the shell of SiO2@dSiO2. Due to the formation of larger-sized crystalline grains, the recombination probability of photogenerated electron-hole pairs was reduced. When used as photocatalysts for the degradation of Rhodamine B under UV irradiation, the catalytic activity of SiO2@dSiO2@TiO2 was 5.4 times higher than that of the commercial P25 TiO2 photocatalyst.

Microstructure and properties of a nano-ZrO2-reinforced AlSi10Mg matrix composite prepared by selective laser melting

In this study, nano-ZrO2-reinforced AlSi10Mg composites were prepared using a high-speed homogenizer and samples were fabricated by selective laser melting (SLM) technique. The effects of ZrO2 on the microstructures, crystallographic textures and mechanical properties of the ZrO2/AlSi10Mg composites were studied. The results show that ZrO2 particles were distributed uniformly and had good interfacial bonding with the AlSi10Mg matrix. The incorporation of ZrO2 reduced the formation of large crystalline grains and had an important role in grain refinement. The small-angle grain boundaries and (001) crystal orientation were greatly enhanced. Compared with AlSi10Mg, ZrO2/AlSi10Mg had superior mechanical properties, including the highest hardness strength of 139 HV (an average increase of 10.3%), a tensile strength of 478.6 MPa and an elongation of 10.6% (increases of 13.5% and 41%, respectively).

Synergistic Effect of Microstructure Engineering and Local Crystal Structure Tuning to Improve the Cycling Stability of Ni-Rich Cathodes

Ultrahigh Ni-rich layered oxides have been regarded as one of the most promising cathode candidates. However, cycling instability induced by interfacial reactions and irreversible H2-H3 lattice distortion is yet to be demonstrated by an effective strategy that could construct a stable grain interface and microstructure. Here, Ni-rich cathode LiNi0.92Co0.05Mn0.03O2 is modified by B and Ti to realize the synchronous regulation of a microstructure and the oxygen framework robustness. Compared with the large equiaxed crystalline grains for the pristine cathode, highly elongated grains with a strong radially oriented crystallographic texture in which the (003) facet is maximized are produced for Ti and B-modified LiNi0.92Co0.05Mn0.03O2. With the suppressed H2-H3 phase transition and cation mixing provided by radially oriented grains and turned local crystal oxygen framework robustness during cycling, the co-modified cathode exhibits enhanced Li+ diffusion kinetics and a capacity retention of 78.3% after 100 cycles, which outperformed the 38.5% for the pristine cathode. The improved cycling performance suggests the significance of the turned microstructure and local crystal structure in suppressing internal strain and crystal structure degradation. The synchronous realization of microstructure engineering and local crystal structure turning by optimal element combination would provide a heuristic solution for the construction of high perform Ni-rich cathodes.

Structure and Superconductivity of Tin-Containing HfTiZrSnM (M = Cu, Fe, Nb, Ni) Medium-Entropy and High-Entropy Alloys.

In an attempt to incorporate tin (Sn) into high-entropy alloys composed of refractory metals Hf, Nb, Ti and Zr with the addition of 3d transition metals Cu, Fe, and Ni, we synthesized a series of alloys in the system HfTiZrSnM (M = Cu, Fe, Nb, Ni). The alloys were characterized crystallographically, microstructurally, and compositionally, and their physical properties were determined, with the emphasis on superconductivity. All Sn-containing alloys are multi-phase mixtures of intermetallic compounds (in most cases four). A common feature of the alloys is a microstructure of large crystalline grains of a hexagonal (Hf, Ti, Zr)5Sn3 partially ordered phase embedded in a matrix that also contains many small inclusions. In the HfTiZrSnCu alloy, some Cu is also incorporated into the grains. Based on the electrical resistivity, specific heat, and magnetization measurements, a superconducting (SC) state was observed in the HfTiZr, HfTiZrSn, HfTiZrSnNi, and HfTiZrSnNb alloys. The HfTiZrSnFe alloy shows a partial SC transition, whereas the HfTiZrSnCu alloy is non-superconducting. All SC alloys are type II superconductors and belong to the Anderson class of “dirty” superconductors.

Ambient Air Temperature Assisted Crystallization for Inorganic CsPbI2Br Perovskite Solar Cells.

Inorganic cesium lead halide perovskites, as alternative light absorbers for organic–inorganic hybrid perovskite solar cells, have attracted more and more attention due to their superb thermal stability for photovoltaic applications. However, the humid air instability of CsPbI2Br perovskite solar cells (PSCs) hinders their further development. The optoelectronic properties of CsPbI2Br films are closely related to the quality of films, so preparing high-quality perovskite films is crucial for fabricating high-performance PSCs. For the first time, we demonstrate that the regulation of ambient temperature of the dry air in the glovebox is able to control the growth of CsPbI2Br crystals and further optimize the morphology of CsPbI2Br film. Through controlling the ambient air temperature assisted crystallization, high-quality CsPbI2Br films are obtained, with advantages such as larger crystalline grains, negligible crystal boundaries, absence of pinholes, lower defect density, and faster carrier mobility. Accordingly, the PSCs based on as-prepared CsPbI2Br film achieve a power conversion efficiency of 15.5% (the maximum stabilized power output of 15.02%). Moreover, the optimized CsPbI2Br films show excellent robustness against moisture and oxygen and maintain the photovoltaic dark phase after 3 h aging in an air atmosphere at room temperature and 35% relative humidity (R.H.). In comparison, the pristine films are completely converted to the yellow phase in 1.5 h.

One-Step Solvent-Free Mechanochemical Incorporation of Insoluble Cesium Salt into Perovskites for Wide Band-Gap Solar Cells

The preparation of high-quality perovskite thin films with a low concentration of defects has recently been achieved through cation engineering using, for example, Cs halide salts. However, many Cs salts cannot be adopted readily due to their frequent insolubility in typical N,N-dimethylformamide (DMF) or dimethyl sulfoxide (DMSO) solvent systems. Herein, we report the application of green, rapid, and solvent-free mechanosynthetic ball-milling for the incorporation of the otherwise insoluble CsBr to realize wide band-gap perovskite solar cells (PSCs). We mechanically synthesize triple-cation (cesium (Cs)/formamidinium (FA)/methylammonium (MA)) wide band-gap perovskites, resulting in subsequent powders that were soluble in mixed DMF/DMSO (4:1, V/V) solvents. Otherwise, the preparation of triple cations for wide band-gap perovskites through conventional solution processing could not be realized. The use of mechanosynthesis perovskites for thin-film formation allows for the growth of relatively large crystalline grains with grains diameter in the range of 500–700 nm. The champion device achieved a maximum PCE of 7.3% (7.03% stabilized), with JSC of 7.08 mA cm–2, VOC of 1.48 V, and a fill factor (FF) of 70%. This performance and voltage are among the highest reported for wide band-gap PSC devices incorporating triple-cation Csx(FAyMA(1–y))(1–x)PbBr3 perovskites. These results show that the use of a mechanosynthetic strategy to add insoluble dopants to wide band-gap perovskites provides a promising strategy for the formation of high-quality films. Furthermore, mechanoperovskite showed higher phase purity, VOC, and efficiency as compared to the conventional solution-processed devices.

Millimeter‐Size All‐inorganic Perovskite Crystalline Thin Film Grown by Chemical Vapor Deposition

AbstractThe chemical vapor deposition (CVD) method is a dry approach that can produce high quality crystals and thin films at large scale which can be easily adapted by industry. In this work, CVD technology is employed to grow high quality, large size all‐inorganic cesium lead bromide perovskite crystalline film for the first time. The obtained films have millimeter size crystalline domains with high phase purity. The growth kinetics are examined in detail by optical microscopy and X‐ray diffraction. The deposition rate and growth temperature are found to be the key parameters allowing to achieve large scale crystal growth. The large crystalline grains exhibit exceptional optical properties including negligible Stokes shift and uniform photoluminescence over a large scale. This suggests a high degree of crystallinity free from internal strain or defects. A lateral diode within one large crystalline grain is further fabricated and significant photo‐generated voltage and short circuit current are observed, suggesting highly efficient carrier transport and collections without scattering within the grain. This demonstration suggests that the CVD grown all‐inorganic perovskite thin films enable a promising fabrication route suitable for photovoltaic or photo‐detector applications.

Bayesian analysis of Juno/JIRAM's NIR observations of Europa

Decades of observations of Europa's surface in the near-infrared (NIR), spanning spacecrafts like Galileo, Cassini and New Horizons, along with ground based observations, have revealed a rich mixture of species on Europa's surface. Adding to the NIR data of Europa, Juno spacecraft's spectrometer JIRAM has observed it in the 2–5 μm wavelength region. Here we present analysis of select spectra from this dataset, focusing on the two forms of water-ice - amorphous and crystalline. We were limited in our ability to include other dominant Europan species, like acid hydrate, due to unavailability of their optical constants over the entire JIRAM wavelength range. We also take this as an opportunity to present a novel Bayesian spectral inversion framework. Traditional spectral fitting methods, for example a grid-based search of parameter space, lack a systematic way to quantify detection significances of the species included in the model, statistically constrain surface properties and explore degenerecies of solution. Our Bayesian inference framework overcomes these shortcomings by confidently detecting amorphous and crystalline ice in the JIRAM data and permits probabilistic constraints on their compositions and average grain sizes to be obtained. We first validate our analysis framework using simulated spectra of amorphous and crystalline ice mixtures and a laboratory spectrum of crystalline ice. We next analyze the JIRAM data and, through Bayesian model comparisons, find that a two-component, intimately mixed model of amorphous and crystalline ice, henceforth referred to as TC-IM, is strongly preferred (at 26σ confidence) over a two-component model of the same materials but where their spectra are areally/linearly mixed. We also find that the TC-IM model is strongly preferred (at > 30σ confidence) over single-component models with only amorphous or crystalline ice, indicating the presence of both these phases of water ice in the data. Given the high SNR of the JIRAM data, abundances and grain sizes of amorphous and crystalline ice are very tightly constrained for the analysis with the TC-IM model. The solution corresponds to a mixture with a very large number density fraction (99.952−0.001+0.001 %) of small (23.12−1.01+1.01 microns) amorphous ice grains, and a very small fraction (0.048−0.001+0.001 %) of large (565.34−1.01+1.01 microns) crystalline ice grains. The overabundance of small amorphous ice grains we find is consistent with previous studies. The maximum-likelihood spectrum of the TC-IM model, however, is in tension with the data in the regions around 2.5 and 3.6 μm, and indicates the presence of non-ice components not currently included in our model. Our new technique therefore holds the promise of being able to identify these minor species hiding in Europan reflectance data in future work and constrain their abundances and physical properties.

High-Performance Photodetectors With X-Ray Responsivity Based on Interface Modified Perovskite Film

High-performance photodetectors based on an interface modified hybrid perovskite film are reported. Large crystalline grains are formed in perovskite layer with less PbI2. The on/off switching ratio higher than 105 is achieved. Owing to the enhanced efficiency in carrier transport and extraction, the photodetector with a modified interface shows a transient response time as fast as 110 ns. In addition, such devices show an X-ray sensitivity up to $67\mu \text{C}$ Gy−1 cm−2. Our work indicates that the use of hybrid perovskite film with interface engineering is a promising method for efficient photon detection in visible light and X rays mainly because of their fast carrier extraction, low cost and easy preparation.