2D Layered Materials for Ultraviolet Photodetection: A Review

Assessing optoelectronic properties of PbI2 monolayer under uniaxial strain from first principles calculations

We report the colloidal synthesis of a series of surfactant-stabilized lead chalcohalide nanocrystals. Our work is mainly focused on Pb4S3Br2, a chalcohalide phase unknown to date that does not belong to the ambient-pressure PbS-PbBr2 phase diagram. The Pb4S3Br2 nanocrystals herein feature a remarkably narrow size distribution (with a size dispersion as low as 5%), a good size tunability (from 7 to ∼30 nm), an indirect bandgap, photoconductivity (responsivity = 4 ± 1 mA/W), and stability for months in air. A crystal structure is proposed for this new material by combining the information from 3D electron diffraction and electron tomography of a single nanocrystal, X-ray powder diffraction, and density functional theory calculations. Such a structure is closely related to that of the recently discovered high-pressure chalcohalide Pb4S3I2 phase, and indeed we were able to extend our synthesis scheme to Pb4S3I2 colloidal nanocrystals, whose structure matches the one that has been published for the bulk. Finally, we could also prepare nanocrystals of Pb3S2Cl2, which proved to be a structural analogue of the recently reported bulk Pb3Se2Br2 phase. It is remarkable that one high-pressure structure (for Pb4S3I2) and two metastable structures that had not yet been reported (for Pb4S3Br2 and Pb3S2Cl2) can be prepared on the nanoscale by wet-chemical approaches. This highlights the important role of colloidal chemistry in the discovery of new materials and motivates further exploration into metal chalcohalide nanocrystals.

https://pubs.acs.org/doi/pdf/10.1021/jacs.0c03577

Nanocrystals of Lead Chalcohalides: A Series of Kinetically Trapped Metastable Nanostructures.

In this work, we used the chemical vapor transport (CVT) method to grow PbI2 crystals using iodine as a self-transporting agent. The crystals’ structure, composition, and uniformity were confirmed by X-ray diffraction (XRD) and electron probe microanalysis (EPMA) measurements. We investigated the band gap energy using absorption spectroscopy measurements. Furthermore, we explored the temperature dependence of the band gap energy, which shifts from 2.346 eV at 300 K to 2.487 eV at 20 K, and extracted the temperature coefficients. A prototype photodetector with a lateral metal–semiconductor–metal (MSM) configuration was fabricated to evaluate its photoelectric properties using a photoconductivity spectrum (PC) and persistent photoconductivity (PPC) experiments. The resonance-like PC peak indicates the excitonic transition in absorption. The photoresponse ILight/IDark-1 is up to 200%.

/pdf/pbi2-single-crystal-growth-and-its-optical-property-study-2snphgubqp.pdf

PbI2 Single Crystal Growth and Its Optical Property Study

Doping in Semiconductor Oxides‐Based Electron Transport Materials for Perovskite Solar Cells Application

As a potential candidate for modern optoelectronics, two-dimensional PbI2 nanosheets have received much attention. In this paper, we report a simple, low-cost cooling supersaturated aqueous solutio...

PbI2 Nanosheets for Photodetectors via the Facile Cooling Thermal Supersaturation Solution Method

The growth dynamics of CH3NH3PbI3 (MAPbI3) perovskite thin films, deposited by thermal evaporation, has been investigated by atomic force microscope and height–height correlation function analysis. The unstable scaling behavior of initial perovskite films exhibiting the growth of islands, resulting in rougher film formation has been observed. After the formation of continuous film, the roughening has been characterized by analyzing the scaling exponent α ~ 0.70, growth exponent β = 0.79 ± 0.057, 1/z = 0.78 ± 0.038, and 2D fast Fourier transform. Anomalous scaling behavior of the MAPbI3 thin films and the formation of the rapid surface roughening are discovered. It is demonstrated that step-edge barrier induced mound growth may play the dominate role in the growth mechanism of MAPbI3 thin films on Si substrates. Further, the growth behavior of MAPbI3 film on ITO substrates is investigated as a comparison, and it reveals that the growth of MAPbI3 thin films is largely affected by the initial substrates underneath the growing films.

https://iopscience.iop.org/article/10.1088/2053-1591/aa7971/pdf

Scaling behavior and morphology evolution of CH3NH3PbI3 perovskite thin films grown by thermal evaporation

Different ratio incorporation of Ag/TiO
 2
 core–shell nanowires (ATCSN) into TiO
 2
 as an electron transport layer of perovskite solar cells (PSCs) is studied. This structure can prevent the formation of silver halides between perovskite and silver nanowire. It is found that because of the effective improvement of light absorption and separation of photo-generated electron–hole pairs, the introduction of ATCSN leads to increase of short current density and photoelectric conversion efficiency (PCE) of PSCs. 20 mg incorporation of ATCSN PSCs exhibits the best performance of PCE and a 17.7% increase is achieved compared to the control sample.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/mnl.2018.5762

Efficiency enhancement of perovskite solar cell by modifying the TiO2 with Ag/TiO2 core–shell nanowires

The invention discloses a production method of silicon stacks. The method comprises the steps that square crystal grains are cut by adopting a two-step method and pre-cutting in the thicken directionof silicon chips to form square crystal grains which are not completely cut, wherein the cutting depth of the silicon chips accounts for (3/5)-(4/5) of the total thickness of the silicon chips; N surfaces of the silicon chips which are pre-cut in the thickness direction are upward placed on crystal grain cracking paper, cutting cuts are placed upward and pressed slightly, so that the square crystal grains which are not completely cut are completely cracking. Then the crystal grains are placed into a suction cup for grain shaking, according to a strict dimension scale relation which is kept bythe size of soldering flakes and the size of the square crystal grains, filling is conducted according to a sequence of alternative filling of the soldering flakes and the crystal grains, scaling powder is evenly sprayed on the surfaces of welding boats, and the welding boats are subjected to low-temperature welding. According to the production method of the silicon stacks, alignment of the crystal grains in advance is not needed before welding, automatic alignment of the crystal grains after welding can be achieved, the production links are simplified, the welding temperature is lowered, theenergy is saved, the yield is high, the area of air holes is low, and the problem of sparse and loose welding is solved.

Production method of silicon stacks

Titanium dioxide (TiO2) nanorods (NR) structure and Chlorine substitution is beneficial to the extraction and diffusion of electrons in perovskite solar cells (PSCs). In this work, different concen...

Effects of Chlorine Addition to TiO2 Nanorods-Based Perovskite Solar Cells

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