Jianxu Ding

Enhanced Optoelectronic Performance on the (110) Lattice Plane of an MAPbBr3 Single Crystal

Hybrid organic-inorganic lead halide perovskites have attracted significant attention due to their impressive optoelectronic properties. MAPbX3 (MA= CH3NH3+, X= Cl, Br or I), the most popular member of this family, has been recognized as an important next-generation optoelectronic materials contender, and remarkable progress has been achieved in both thin films and single crystals. However, the lack of optimizations in energy harvest, transportation, carrier extraction, and process compatibility is hindering their future development. In this study, a triangle prism MAPbBr3 single crystal exposing (100) and (110) crystallographic planes was successfully synthesized, and the optoelectronic performances of these two lattice planes were systematically explored by employing a planar metal-semiconductor-metal (MSM) device. Compared to the device fabricated on the (100) plane, a 153.33% enhancement of responsivity was achieved under 10 μW irradiation and 10 V bias on the (110) plane. Finally, possible mechanism for such an enhancement was discussed based on the different defect migration behaviors of (100) and (110) planes.

Synthesis and Characterization of Conductive and Soluble Itaconic Acid Doped Polyaniline Nanorods

Nanostructured polyaniline has attracted more attention due to its interesting properties and potential applications. In this paper, itaconic acid doped polyaniline nanorods were successfully synthesized via chemical oxidation polymerization under the optimal polymerization condition obtained by the previous orthogonal experiment design and characterized by various measurements. The itaconic acid doped polyaniline has high productivity up to 94.5%, the conductivity of 2.11×10−2 S/cm and good solubility in organic solvents. Its particle size distribution is mono-dispersed and the morphology is the interconnected nanorods with the diameter of 67 nm. The crystallinity of itaconic acid doped polyaniline is 39.36%, but that of undoped polyaniline is 14.92%, as indicates that the existence of the dopant intensifies the order of the polyaniline crystal structure. There is a classic and specific absorption peak at 1243 cm−1 for doped polyaniline. The weight loss of itaconic acid doped polyaniline is mainly caused by the dedoping of the dopant and the decomposition of polyaniline backbone.

Experiments Proving the Mixed Control of the Reactive Diffusion System Zn/Fe3Si with Clamp Press

More than twenty years were needed for people to understand the formation mechanism of the periodic-layered structures not only because of the complications of pattern formation, but also due to the limits of traditional diffusion theories. Based on the general theory of interdiffusion growth proposed by Y.C. Chen et al. [1], the quantitative model of periodic layer formation during solid state reactions has been succeeded [2]. The experimental results shown in this paper proved one of the model’s predicts that the reactive diffusion system Zn/Fe3Si with clamp press annealed at 663K should be mixed controlled. Also, the important influence of the uniaxial compressive stress on the diffusion coefficient was emphasized and the reasons are discussed.

Polarization-Dependent Optoelectronic Performances in Hybrid Halide Perovskite MAPbX3 (X = Br, Cl) Single-Crystal Photodetectors

Hybrid organic-inorganic lead halide perovskites (HOIPs) have received significant attention because of their impressive performances in the fields of solar cells and photoelectric detection. In the past five years, great efforts have been made to improve the crystallinity, reduce grain boundaries, and enhance the stabilities of perovskite films. Compared with films, HOIP single crystals possess fewer grain boundaries and stronger optoelectronic properties and can be applied in optoelectronic devices. As the most popular HOIP member, single crystals of MAPbX3 (X = Br, Cl) are deemed as important candidates for ultraviolet-visible photodetectors, in which the crystal structure anisotropy largely affects the detection performance. In this study, high-quality cubic single crystals of MAPbBr3 and MAPbCl3 were successfully grown from solutions. Taking advantages of their smooth (100) facets, planar metal-semiconductor-metal photodetectors were fabricated using Au interdigitated electrodes. The optoelectronic performances under nonpolarized and linearly polarized lights were explored. The optoelectronic performances were dependent on linearly polarized lights. Interestingly, both responsivity and external quantum efficiency were greatly enhanced under the excitation with linearly polarized lights. Moreover, the polarization-related optical absorptions and the electron densities within the (100) plane could be used to interpret different optoelectronic performances of single crystals of MAPbX3 (X = Br, Cl) under various linearly polarized lights.

Design Growth of MAPbI3 Single Crystal with (220) Facets Exposed and Its Superior Optoelectronic Properties

MAPbI3 is deemed as the most prominent member in hybrid perovskites family because of its extremely optoelectronic properties. However, some issues and puzzles are still in expectation of their answers, such as stabilities, hysteresis, ferroelectricity, and so on. To bridge the distinctions between MAPbI3 single crystal and thin films, large-size single crystals are demanded. On the contrary, crystal structure anisotropy-dependent optoelectronic properties is an inevitable topic. A series of large-size MAPbI3 single crystals with (220) facets exposed were successfully grown, using high concentration solutions and large-size seed crystals to match growth rates of (100) and (220) facets. The optoelectronic properties of photocurrents, responsivity, EQE, and detectivity clearly showed significant anisotropy of optoelectronic properties in MAPbI3 single crystal. According to ion migration theory, the anisotropy of optoelectronic properties was interpreted. We hope this result will be helpful to guide oriented growth MAPbI3 thin films.

Crystal orientation-dependent optoelectronic properties of MAPbCl3 single crystals

Hybrid perovskite MAPbCl3 is considered to be one of the most promising candidates applied in visible-blind UV-photo-detectors due to its outstanding optoelectronic properties. It is proved that the MAPbCl3 single crystal is more excellent than its polycrystalline counterpart because of its fewer defects and grain boundaries. When referring to a single crystal, the crystal orientation or crystal structure anisotropy is an inevitable topic, because structure anisotropy can affect or decide the optoelectronic properties of single crystals. In this study, both cubic and triangular prism MAPbCl3 single crystals with (100) and (110) crystallographic planes were successfully grown from mixed solutions. The crystal growth process, crystal structure and optical absorption were investigated. Moreover, by fabricating metal–semiconductor–metal (MSM) photo-detectors using Au interdigital electrodes on both (100) and (110) planes, the optoelectronic anisotropy was explored by comparing photocurrents, responsivity, external quantum efficiency and detectivity. According to the crystal structure and calculated charge density, the optoelectronic anisotropy in the MAPbCl3 single crystal was revealed.

Incorporation of Cesium Ions into MA1–xCsxPbI3 Single Crystals: Crystal Growth, Enhancement of Stability, and Optoelectronic Properties

Organic-inorganic hybrid methylammonium lead iodide perovskite (MAPbI3) has attracted extensive attention in a series of optoelectronic devices. The photoelectric properties of the MAPbI3 single crystal have been revealed to be much better than those of it polycrystalline counterparts. However, its poor moisture and heat resistance severely limited further development. The introduction of Cs+ into polycrystalline films has shown to be an effective way to enhance its moisture resistance through a passivation effect. However, the entrance abilities of Cs+ into a MAPbI3 crystal lattice and the influence on photoelectric properties of a single crystal were not clear until now. Therefore, we attempted to grow large MA1- xCs xPbI3 single crystals to introduce Cs+ into the crystal lattice. The existence of Cs+ brought lattice shrinkage and enhanced stability of the MAPbI3 single crystal. A moderate quantity of Cs+ (2%) proved to heighten the photoelectric properties, whereas an excess quantity of Cs+ (5%) brought more shallow defects, which ultimately deteriorated the photoelectric properties.