PbI2 Nanosheets Research Articles

Ligand-Induced In Situ Epitaxial Growth of PbI2 Nanosheets/MAPbI3 Heterojunction Realizes High-Performance HTM-Free Carbon-Based MAPbI3 Solar Cells.

Hole-transporting layer-free carbon-based perovskite solar cells (HTL-free C-PSCs) hold great promise for photovoltaic applications due to their low cost and outstanding stability. However, the low power conversion efficiency (PCE) of HTL-free C-PSCs mainly results from grain boundaries (GBs). Here, epitaxial growth is proposed to rationally design a hybrid nanostructure of PbI2 nanosheets/perovskite with the desired photovoltaic properties. A post-treatment technique using tri(2,2,2-trifluoromethyl) phosphate (TFEP) to induce in situ epitaxial growth of PbI2 nanosheets at the GBs of perovskite films realizes high-performance HTL-free C-PSCs. The structure model and high-resolution transmission electron microscope unravel the epitaxial growth mechanism. The epitaxial growth of oriented PbI2 nanosheets generates the PbI2/perovskite heterojunction, which not only passivates defects but forms type-I band alignment, avoiding carrier loss. Additionally, Fourier-transform infrared spectroscopy, 31P NMR, and 1H NMR spectra reveal the passivation effect and hydrogen bonding interaction between TFEP and perovskite. As a result, the VOC is remarkably boosted from 1.04 to 1.10V, leading to a substantial gain in PCE from 14.97% to 17.78%. In addition, the unencapsulated PSC maintains the initial PCE of 80.1% for 1440h under air ambient of 40% RH. The work offers a fresh perspective on the rational design of high-performance HTL-free C-PSCs.

High‐Performance UV Photodetector via Energy Band Engineering and LSPR‐Enhanced Pyro‐Phototronic Effect in Au Decorated 2D‐PbI2/1D‐ZnO Heterojunction

AbstractUltraviolet (UV) photodetectors have attracted extensive attention in various applications, including aerospace, optical communication, and fire warning. However, the intrinsic coupling of high responsivity and fast response as well as imperfect interface transmission impede the further improvement of UV photodetector. Here, a high‐performance Au‐decorated PbI2/ZnO pn junction UV photodetector with a one‐dimensional (1D) and two‐dimensional (2D) interspersed structure is presented. The pyro‐phototronic effect and energy band engineering effect from the localized pn junction generated by the layered p‐type PbI2 nanosheets along the c‐axis of ZnO are coupled to modulate the separation and transport of photogenerated carriers. Furthermore, the localized surface plasmon resonance of Au nanoparticles produces transient thermal power to raise temperature fast to enhance pyroelectric current. The self‐powered Au@PbI2/ZnO photodetector displays a high responsivity of 0.21 A W−1, excellent detectivity of 7.9 × 1012 Jones, and fast response/recovery time of 25/31 ms, under the illumination of 325 nm light with the power density of 0.08 µW cm−2. This work offers an effective strategy for designing high‐performance next‐generation optoelectronic devices.

Synthesis of tungsten-doped PbI2 nanostructure

Facile synthesis of the microwave was applied to assist in synthesizing pure and tungsten-doped lead iodide (W: PbI2) nanosheets with less than 100 nm thickness. The proposed W-doped PbI2 nanosheets were subjected to various characterization, including structural, morphological, spectral, optical, dielectric, and radiation studies. SEM and EDX investigations confirmed that the tungsten dopants affect the undoped PbI2 matrix. The structural morphology from XRD patterns approved the good crystallinity of the prepared W-doped PbI2 nanostructures. Optical characterizations revealed the energy band structure of the grown materials. The dielectric constant of the W-doped PbI2 nanostructures varied from 23 to 31, confirming the increasing dielectric trend with increasing W doping concentrations. The Gamma linear absorption coefficient value was found to vary between 9.2 and 15 in case Am-241, suggesting various applications in radiation detectors for the prepared W-doped PbI2 nanostructured sheets.

Facile microwave synthesis of tungsten-doped PbI2 nanostructures for optoelectronic and radiation detection devices

Facile synthesis of the microwave was applied to assist in synthesizing pure and tungsten-doped lead iodide (W: PbI2) nanosheets with less than 100 nm thickness. The proposed W-doped PbI2 nanosheets were subjected to various characterization, including structural, morphological, spectral, optical, dielectric, and radiation studies. SEM and EDX investigations confirmed that the tungsten dopants affect the undoped PbI2 matrix. The structural morphology from XRD patterns approved the good crystallinity of the prepared W-doped PbI2 nanostructures. Optical characterizations revealed the energy band structure of the grown materials. The dielectric constant of the W-doped PbI2 nanostructures varied from 23 to 31, confirming the increasing dielectric trend with increasing W doping concentrations. The Gamma linear absorption coefficient value was found to vary between 9.2 and 15 in case Am-241, suggesting various applications in radiation detectors for the prepared W-doped PbI2 nanostructured sheets.

Nonlinear microscopy of lead iodide nanosheets.

Lead iodide (PbI2) is a van der Waals layered semiconductor with a direct bandgap in its bulk form and a hexagonal layered crystalline structure. The recently developed PbI2 nanosheets have shown great promise for high-performance optoelectronic devices, including nanolasers and photodetectors. However, despite being widely used as a precursor for perovskite materials, the optical properties of PbI2 nanomaterials remain largely unexplored. Here, we determine the nonlinear optical properties of PbI2 nanosheets by utilising nonlinear microscopy as a non-invasive optical technique. We demonstrate the nonlinearity enhancement dependent on excitonic resonances, crystalline orientation, thickness, and influence of the substrate. Our results allow for estimating the second- and third-order nonlinear susceptibilities of the nanosheets, opening new opportunities for the use of PbI2 nanosheets as nonlinear and quantum light sources.

Deeper Insight into the Role of Organic Ammonium Cations in Reducing Surface Defects of the Perovskite Film

AbstractOrganic ammonium salts (OASs) have been widely used to passivate perovskite defects. The passivation mechanism is usually attributed to coordination of OASs with unpaired lead or halide ions, yet ignoring their interaction with excess PbI2 on the perovskite film. Herein, we demonstrate that OASs not only passivate defects by themselves, but also redistribute excess aggregated PbI2 into a discontinuous layer, augmenting its passivation effect. Moreover, alkyl OAS is more powerful to disperse PbI2 than a F‐containing one, leading to better passivation and device efficiency because F atoms restrict the intercalation of OAS into PbI2 layers. Inspired by this mechanism, exfoliated PbI2 nanosheets are adopted to provide better dispersity of PbI2, further boosting the efficiency to 23.14 %. Our finding offers a distinctive understanding of the role of OASs in reducing perovskite defects, and a route to choosing an OAS passivator by considering substitution effects rather than by trial and error.

Deeper Insight into the Role of Organic Ammonium Cations in Reducing Surface Defects of the Perovskite Film.

Organic ammonium salts (OASs) have been widely used to passivate perovskite defects. The passivation mechanism is usually attributed to coordination of OASs with unpaired lead or halide ions, yet ignoring their interaction with excess PbI2 on the perovskite film. Herein, we demonstrate that OASs not only passivate defects by themselves, but also redistribute excess aggregated PbI2 into a discontinuous layer, augmenting its passivation effect. Moreover, alkyl OAS is more powerful to disperse PbI2 than a F-containing one, leading to better passivation and device efficiency because F atoms restrict the intercalation of OAS into PbI2 layers. Inspired by this mechanism, exfoliated PbI2 nanosheets are adopted to provide better dispersity of PbI2 , further boosting the efficiency to 23.14 %. Our finding offers a distinctive understanding of the role of OASs in reducing perovskite defects, and a route to choosing an OAS passivator by considering substitution effects rather than by trial and error.

Light Industry Technology of Chiral Perovskite Nanomaterials Construction and Photoelectric Properties

Perovskite nanomaterials have become a new research hotspot due to the many novel physical properties of quantum effects and have good application prospects in the field of optoelectronics. Among them, the realization of controllable fabrication of perovskite nanomaterials is the basis of performance studies and applications and is also a difficult point. Reducing production costs to improve manufacturing methods, further improve product controllability, promote advantages, or improve disadvantages will be very important for further application of perovskite nanomaterials. Therefore, this paper studies the construction of titanium ore nanomaterials by designing a novel preparation process and, at the same time, analyzes the related optoelectronic properties of the obtained materials. In this paper, a triangular PbI2 nanosheet having a uniform and controllable shape and size was successfully fabricated by physical vapor deposition through the introduction of a limited space, and related characterization was performed to show uniform controllability and high crystallinity. Using PbI2 nanosheets as the substrate, MAPbI3 nanosheets were further prepared and related characterizations proved that the obtained nanosheets had high crystallinity and excellent optical properties. The experiment proves that the peak position of the fluorescence spectrum obtained by Gaussian fitting is 800 nm and the half‐peak width is about 45 nm. At the same time, MAPbI3 exhibits strong light absorption characteristics when the wavelength is less than 800 nm. This shows that this enclosed space deposition method can improve the uniformity and controllability of PbI2 and MAPbI3 nanosheet fabrication, which provides the basis for further research on MAPbI3 nanomaterials and references to the controllable growth of other nanomaterials.

Insight on the optoelectronics and enhanced dielectric properties of strontium decorated PbI2 nanosheets for hot carrier solar cell applications

Dielectric properties determine by electric field distributions play a decisive role in energy harvesting and storage applications. In this context, strontium decorated lead iodide nanosheets (Sr:PbI2) are prepared, and its vibrational and dielectric properties are studied. The bandgap changes are explained by Brustein-Moss effect and renormalization process. Raman spectral studies reveal that introducing Sr atoms into PbI2 lattice enhance the lifetime of LO phonon through bottleneck effect. Subsequently, the dielectric constant (ε′) values of 5 wt% Sr:PbI2 are increased 20% than pure PbI2. The results conclude that the vibrational properties of Sr decorated PbI2 nanosheets are much significant for hot carrier solar cell devices.

Novel rare earth Dy doping impact on physical properties of PbI2 nanostructures synthesized by microwave route for optoelectronics

Dysprosium (Dy) doped lead iodide (PbI2) nanostructures (Dy@PbI2 NSs) were facilely synthesized via microwave-assisted route for the first time and studied by state-of-art experimental tools. Energy dispersive X-ray spectroscopy/scanning electron microscopy (EDX/SEM) elemental-mapping confirm the presence of Dy doping and its standardized dispersal in PbI2 and hexagonal shape nanosheets morphology along with fine nanoparticles was also confirmed. Monophasic hexagonal phase confirmation was carried out using X-ray diffractometry (XRD) and Rietveld refinement, which was further approved via vibrational analysis. The Scherrer rule was employed to determine the size, dislocations and strain in final products and the size was noted between 46 and 53 nm. The energy gap was evaluated for all Dy@PbI2 NSs and noticed to lie between 3.14 and 3.19 eV. Room temperature Photoluminescence emission (RTPLE) was recorded for all Dy@PbI2 NSs at excitation wavelength of 221 nm, which contains one shoulder and three major emission peaks at 455 ± 3 nm, 373 ± 2 nm, 469 ± 2 nm, 528 ± 5 nm. Both quenching and enhancement in PL intensity was observed with Dy doping. Detailed dielectric and electrical analyses were carried out and highest dielectric constant and conductivity was noted for 0.2 wt% Dy@PbI2 NSs. The outcomes indicated that the prepared Dy@PbI2 NSs are good contender for optoelectronics.

Avantium weathers 1H 2020, Catalysis business impacted by pandemic

Dysprosium (Dy) doped lead iodide (PbI2) nanostructures ([email protected]2 NSs) were facilely synthesized via microwave-assisted route for the first time and studied by state-of-art experimental tools. Energy dispersive X-ray spectroscopy/scanning electron microscopy (EDX/SEM) elemental-mapping confirm the presence of Dy doping and its standardized dispersal in PbI2 and hexagonal shape nanosheets morphology along with fine nanoparticles was also confirmed. Monophasic hexagonal phase confirmation was carried out using X-ray diffractometry (XRD) and Rietveld refinement, which was further approved via vibrational analysis. The Scherrer rule was employed to determine the size, dislocations and strain in final products and the size was noted between 46 and 53 nm. The energy gap was evaluated for all [email protected]2 NSs and noticed to lie between 3.14 and 3.19 eV. Room temperature Photoluminescence emission (RTPLE) was recorded for all [email protected]2 NSs at excitation wavelength of 221 nm, which contains one shoulder and three major emission peaks at 455 ± 3 nm, 373 ± 2 nm, 469 ± 2 nm, 528 ± 5 nm. Both quenching and enhancement in PL intensity was observed with Dy doping. Detailed dielectric and electrical analyses were carried out and highest dielectric constant and conductivity was noted for 0.2 wt% [email protected]2 NSs. The outcomes indicated that the prepared [email protected]2 NSs are good contender for optoelectronics.

Ligand-Modulated Excess PbI2 Nanosheets for Highly Efficient and Stable Perovskite Solar Cells.

Excess lead iodide (PbI2 ), as a defect passivation material in perovskite films, contributes to the longer carrier lifetime and reduced halide vacancies for high-efficiency perovskite solar cells. However, the random distribution of excess PbI2 also leads to accelerated degradation of the perovskite layer. Inspired by nanocrystal synthesis, here, a universal ligand-modulation technology is developed to modulate the shape and distribution of excess PbI2 in perovskite films. By adding certain ligands, perovskite films with vertically distributed PbI2 nanosheets between the grain boundaries are successfully achieved, which reduces the nonradiative recombination and trap density of the perovskite layer. Thus, the power conversion efficiency of the modulated device increases from 20% to 22% compared to the control device. In addition, benefiting from the vertical distribution of excess PbI2 and the hydrophobic nature of the surface ligands, the modulated devices exhibit much longer stability, retaining 72% of their initial efficiency after 360 h constant illumination under maximum power point tracking measurement.

Growth and characterization of PbI2-decorated ZnO nanowires for photodetection applications

In this study, we demonstrated for the first time the growth of ZnO nanowires (NWs) decorated with highly crystalline few-layer PbI2 and fabricated two-terminal single-nanowire photodetector devices to investigate the photoelectric properties of the hybrid nanostructures. We developed a novel two-step growth process for uniform crystalline PbI2 nanosheets via reactive magnetron deposition of a lead oxide film followed by subsequent iodination to PbI2 on a ZnO NW substrate, and we compared as-grown hybrid nanostructures with ones prepared via thermal evaporation method. ZnO–PbI2 NWs were characterized by scanning and transmission electron microscopy, X-ray diffraction analysis and photoluminescence measurements. By fabricating two-terminal single-nanowire photodetectors of the as-grown ZnO–PbI2 nanostructures, we showed that they exhibit reduced dark current and decreased photoresponse time in comparison to pure ZnO NWs and have responsivity up to 0.6 A/W. Ab initio calculations of the electronic structure of both PbI2 nanosheets and ZnO NWs have been performed, and show potential for photoelectrocatalytic hydrogen production. The obtained results show the benefits of combining layered van der Waals materials with semiconducting NWs to create novel nanostructures with enhanced properties for applications in optoelectronics or X-ray detectors.

Liquid Exfoliation of Two-Dimensional PbI2 Nanosheets for Ultrafast Photonics

Two-dimensional (2D) materials are showing promise in next-generation optoelectronic devices. To this end, large-scale production of defect-free 2D nanosheets is vital. Herein, we demonstrate scalable exfoliation and preparation of high-quality 2D PbI2 nanosheets in cyclopentanone. The resulting dispersions can retain good stability over 30 days and can also sustain freezing treatment. The exfoliation kinetics was observed to fit an apparent pseudo-first-order process. Furthermore, the PbI2 nanosheets exhibit excellent saturable absorption properties both at femtosecond and nanosecond pulse excitations in the visible region, thus showing potential application in the field of ultrafast saturable absorbers.

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

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...

Excitonic effects on layer- and strain-dependent optoelectronic properties of PbI2

Exciton states have obvious effects on optical properties of two-dimensional (2D) materials. Here, we investigate excitonic effects on electronic and optical properties of PbI2 by using G0W0 + Bethe-Salpeter equation method, considering the layer number and strain effect. These studies show that exciton states obviously modify and dominate the optical absorption of 2D PbI2 nanosheets. Also, with the increasing number of layers, the intensity of main absorption peak increases and the exciton binding energy decreases. Meanwhile, the tensile strain can induce the threshold energy of optical spectra shift down the low energy, and exciton binding energy has a maximum at the strain of 3%. Therefore, our results indicate that the 2D PbI2 nanomaterials have excellent ultraviolet absorption and corresponding potential for the application of optoelectronic devices.

Lead Iodide Nanosheets For Piezoelectric Energy Conversion And Strain Sensing

Abstract Flexible piezoelectric devices are attractive for energy conversion and strain sensing applications, including in the area of wearable electronics and self-powered sensors. Here, we report a piezoelectric nanogenerator/strain sensor based on lead (II) iodide (PbI2) nanosheets with the shape of two-dimensional (2D) structures, of which the piezoelectricity is not affected by the number of layers. A typical 2D piezoelectric device fabricated with 3 layers PbI2 nanosheets has recorded peak values of open-circuit voltage, short-circuit current and loading power as 29.4 mV, 20 pA, and 0.12 pW, respectively, and also possess good charging and integration capabilities. Moreover, these devices can be applied as self-powered strain sensors, with high sensitivity and excellent stability. As such, this study provides new knowledge and strategy for flexible energy harvesting or strain sensing devices based on 2D structures.

Microwave-synthesis of La3+ doped PbI2 nanosheets (NSs) and their characterizations for optoelectronic applications

Herein, we report the microwave-synthesis of pure and lanthanum (La3+) doped PbI2 nanostructures. Single phase and good crystallinity confirmation was done using X-ray diffraction and FT-Raman spectroscopy analyses. Presence of La in the final product was proved by energy dispersive X-ray spectroscopy and homogeneous doping of La was seen in EDX elemental mapping. Vibrational modes of final products gets shifted compare to bulk values which evidently specify more relaxed nanostructure formation. The morphology was determined by scanning electron microscope analysis which was nanorods (NRs) of dimension in range of 70–100 nm of pure. However, when doped with 1% La the formation of nanosheets (NSs) are found to be more dense with well defined hexagonal morphology and the average thickness is found to be reduced which is ~ 57 nm and size is increased. Ultra violet–visible–near infrared measurement was done and the energy gap was computed, which are in range of ~ 2.93 to 3.26 eV. Photoluminescence emission spectra was recorded at $${\lambda _{exc}}=221\;{\text{nm}}$$ . PL emissions positioned at ~ 470 ± 2 and 525 ± 7 nm are corresponding to blue and green emissions in NSs. An enhancement in values of dielectric and electrical conductivity was observed due to doping.

Facile one pot synthesis of novel Hg2+ doped PbI2 nanostructures for optoelectronic and radiation shielding applications

Facile one pot synthesis of pure and Hg2+ (= 0.101 nm) doped PbI2 (Pb2+ = 0.133 nm) single crystalline nanoplates (NPs), nanosheets (NSs) and nanorods (NRs) were achieved through chemical route at room temperature. The single phase and high quality of the synthesized NPs, NSs and NRs was proved by X-ray diffraction and FT-Raman spectroscopic analyses. The lattice constants, crystallite size, lattice strain, dislocation density were calculated. The crystallite size was calculated to be in the range of 16–22 nm. The Hg doping in PbI2 was approved by energy dispersive X-ray spectroscopy (EDXS) and its homogeneous distribution was confirmed by scanning electron microscopy (SEM) mapping. The morphology of pure and doped synthesized nanostructures was observed to be single crystalline NPs, NSs and NRs of nanoscale thicknesses. The optical band gap was calculated from Tauc's plot and found to be in the range of 3.27–3.20 eV. The value of dielectric constant was improved from 20 to 25 and also ac electrical conductivity due to Hg2+ doping. The radiation parameters such as linear absorption coefficient, half value layer, tenth value layer and mean free path were calculated and a remarkable enhancement was observed due to Hg2+ doping. These parameters confirm that the nanostructures are highly sensitive to 214Am 59.5KeV γ-ray. The facilely synthesized nanostructures of PbI2 with enhanced properties due to Hg2+ doping makes them more suitable for nanoelectronics and room temperature radiation detector applications.

Lead iodide nanosheets for piezoelectric energy conversion and strain sensing

Flexible piezoelectric devices are attractive for energy conversion and strain sensing applications, including in the area of wearable electronics and self-powered sensors. Here, we report a piezoelectric nanogenerator/strain sensor based on lead (II) iodide (PbI2) nanosheets with the shape of two-dimensional (2D) structures, of which the piezoelectricity is not affected by the number of layers. A typical 2D piezoelectric device fabricated with 3 layers PbI2 nanosheets has recorded peak values of open-circuit voltage, short-circuit current and loading power as 29.4 mV, 20 pA, and 0.12 pW, respectively, and also possess good charging and integration capabilities. Moreover, these devices can be applied as self-powered strain sensors, with high sensitivity and excellent stability. As such, this study provides new knowledge and strategy for flexible energy harvesting or strain sensing devices based on 2D structures.