Permanent Lattice Compression of Lead-Halide Perovskite for Persistently Enhanced Optoelectronic Properties

Under mild mechanical pressure, halide perovskites show enhanced optoelectronic properties. However, these improvements are reversible upon decompression, and permanent enhancements have yet to be ..

Thiocyanate-Treated Perovskite-Nanocrystal-Based Light-Emitting Diodes with Insight in Efficiency Roll-Off

Light emitting diodes (LED) based on halide perovskite nanocrystals (NC) have received widespread attention in recent years. In particular, LEDs based on CsPbBr3 NCs were the object of special interest. Here, we report for the first time green LED based on CsPbBr3 NCs treated with ammonium thiocyanate solution before purification with polar solvent. The champion device fabricated based on the treated CsPbBr3 NCs showed high efficiency and high stability during operation as well as during storage. A study on morphology and current distribution of NC films under applied voltages was carried out by conductive atomic force microscopy, giving a hint on efficiency roll-off. The current work provides a facile way to treat sensitive perovskite NCs and to fabricate perovskite NC-based LED with high stability. Moreover, the results shed new light on the relation between film morphology and device performance and on the possible mechanism of efficiency roll-off in NC LED

An insight into the electrochemical activity of Al-doped V2O3

We design Al-doped V2O3 (AlxV2O3) compounds as cathodes of aluminium battery. A citric acid-assisted simple solid-state synthesis is used to produce AlxV2O3 compounds by heating, at different temperature, a reaction mixture of NH4VO3, Al(NO3)3centerdot9H2O and citric acid under Ar flow. Al-doping in-between layers and at lattice sites of V2O3 is confirmed by structural, vibrational and chemical analyses. The doped compounds obtained at 600 °C and 800 °C are confirmed as Al0.56V2O3 and Al0.53V2O3 corresponding to theoretical capacities 488 and 490 mAh g−1, respectively, for the extraction of doped Al by considering three electron transfer (Al/Al3+). The as-synthesized AlxV2O3 compounds are tested as cathodes in aluminium battery with 1.0 M AlCl3:[EMIM]Cl electrolyte. The electrodes of Al0.56V2O3 and Al0.53V2O3 exhibited the first charge capacity of 415 and 385 mAh g−1, respectively. The electrochemical extraction of doped Al is confirmed by comparisons with bare V2O3 control cathodes and post-cycling structural studies. The extraction of doped Al from AlxV2O3 indicates its promising use in high capacity cathode for Al-ion battery.NRF (Natl Research Foundation, S’pore)Published versio

A novel ball milling technique for room temperature processing of TiO2 nanoparticles employed as the electron transport layer in perovskite solar cells and modules

A novel ball milling method was used to prepare TiO2 ETMs at RT ∼ 30 °C for large and small area perovskite solar cells

Photovoltaic Performance of Vapor-Assisted Solution-Processed Layer Polymorph of Cs₃Sb₂I₉

The presence of toxic lead (Pb) remains a major obstruction to the commercial application of perovskite solar cells. Although antimony (Sb)-based perovskite-like structures A₃M₂X₉ can display potentially useful photovoltaic behavior, solution-processed Sb-based perovskite-like structures usually favor the dimer phase, which has poor photovoltaic properties. In this study, we prepared a layered polymorph of Cs₃Sb₂I₉ through solution-processing and studied its photovoltaic properties. The exciton binding energy and exciton lifetime of the layer-form Cs₃Sb₂I₉ were approximately 100 meV and 6 ns, respectively. The photovoltaic properties of the layered polymorph were superior to those of the dimer polymorph. A solar cell incorporating the layer-form Cs₃Sb₂I₉ exhibited an open-circuit voltage of 0.72 V and a power conversion efficiency of 1.5%the highest reported for an all-inorganic Sb-based perovskite

UV- and NIR-Protective Semitransparent Smart Windows Based on Metal Halide Solar Cells

In this study, a solution-processable lead iodide semiconductor having a wide band gap was investigated as a light absorbing material for various organic electron transport materials, in a search for low-cost semiconductor materials allowing the facile fabrication of efficient photovoltaic devices. A Tauc plot suggested a wide intrinsic optical band gap of 2.4 eV for a thin film of PbI₂, while X-ray diffraction revealed that the spin-coated PbI₂ thin film had a hexagonal crystalline structure with preferable orientation along the (001) plane. The effect of the light intensity on the values of <i>V</i>_oc and <i>J</i>_sc was studied to investigate the charge recombination mechanism of fabricated devices. An efficient bifacial solar cell was prepared featuring a thin Ag film sandwiched between BCP and MoO₃ layers as a transparent rear electrode. The whole device featuring the BCP/Ag/MoO₃ electrode exhibited a maximum transmittance of approximately 60% in the visible region, less than 15% in the UV region, and less than 25% in the NIR region. A power conversion efficiency of 2.19% was achieved for a device featuring an opaque electrode (Ca/Al), while the corresponding device featuring the transparent electrode (BCP/Ag/MoO₃) provided values of 0.75% and 0.67% when illuminated from the front and rear, respectively. Thus, wide band gap metal halide materials potentially open up a new path for fabricating efficient and transparent photovoltaic devices having applications as building-integrated smart windows. It also effectively prevents the penetration of UV and NIR light, which is harmful for human health, into the building

Whispering Gallery Mode Lasing from Self-Assembled Hexagonal Perovskite Single Crystals and Porous Thin Films Decorated by Dielectric Spherical Resonators

Lasing in self-assembled hybrid organic–inorganic lead halide perovskites semiconductors has attained intensive research for low cost and high performance optoelectronic devices due to their inherent outstanding optical response. However, to achieve the controllable laser action from a small single crystal remains as a challenging issue. Here, we present a novel technique to fabricate self-assembled high-quality hexagonal perovskite single crystals for realizing room-temperature near-infrared whispering-gallery-mode (WGM) laser action. Quite interestingly, the lasing spectrum for an individual CH₃NH₃PbI₃ hexagonal single crystals encompasses the aspects of high quality factor (<i>Q</i>) and low threshold WGM lasing around 1200 and 26.8 μJ/cm², respectively. In addition, we demonstrate that when the porous perovskite thin films were decorated with dielectric spheres, the laser oscillation can be achieved through the coupling of WGM with perovskite gain material. We found that the lasing spectra can be well manipulated by the size of hexagonal single crystals and SiO₂ spheres. Moreover, the discovered laser action and chemical stability of hexagonal single crystal perovskites not only render them significant practical use in highly efficient near-infrared emitting devices for laser photonics, solid-state lighting, and display applications, but also provide a potential extension toward various optoelectronic devices

Bifacial Perovskite Solar Cells Featuring Semitransparent Electrodes

Inorganic–organic hybrid perovskite solar cells (PSCs) are promising devices for providing future clean energy because of their low cost, ease of fabrication, and high efficiencies, similar to those of silicon solar cells. These materials have been investigated for their potential use in bifacial PSCs, which can absorb light from both sides of the electrodes. Here, we fabricated bifacial PSCs featuring transparent BCP/Ag/MoO₃ rear electrodes, which we formed through low-temperature processing using thermal evaporation methods. We employed a comprehensive optical distribution program to calculate the distributions of the optical field intensities with constant thicknesses of the absorbing layer in the top electrode configuration. The best PSC having a transparent BCP/Ag/MoO₃ electrode achieved PCEs of 13.49% and 9.61% when illuminated from the sides of the indium tin oxide and BCP/Ag/MoO₃ electrodes, respectively. We observed significant power enhancement when operating this PSC using mirror reflectors and bifacial light illumination from both sides of the electrodes

Using an Airbrush Pen for Layer-by-Layer Growth of Continuous Perovskite Thin Films for Hybrid Solar Cells

In this manuscript we describe hybrid heterojunction solar cells, having the device architecture glass/indium tin oxide/poly­(3,4-ethylenedioxythiopene)/poly­(styrenesulfonic acid)/perovskite/[6,6]-phenyl-C₆₁-butyric acid methyl ester/C₆₀/2,9-dimethyl- 4,7-diphenyl-1,10-phenanthroline/Al, fabricated using lead halide perovskite obtained through spray-coating at a low precursor concentration. To study the relationship between the morphology and device performance, we recorded scanning electron microscopy images of perovskite films prepared at various precursor ratios, spray volumes, substrate temperatures, and postspray annealing temperatures. Optimization of the spray conditions ensured uniform film growth and high surface area coverage at low substrate temperatures. Lead halide perovskite solar cells prepared under the optimal conditions displayed an average power conversion efficiency (PCE) of approximately 9.2%, with 85% of such devices having efficiencies of greater than 8.3%. The best-performing device exhibited a short-circuit current density of 17.3 mA cm^–2, a fill factor of 0.63, and an open-circuit voltage of 0.93 V, resulting in a PCE of 10.2%. Because spray-coating technology allows large-area deposition, we also fabricated devices having areas of 60 and 342 mm², achieving PCEs with these devices of 6.88 and 4.66%, respectively

Mitigating Metal Dendrite Formation in Lithium-Sulfur Batteries via Morphology-Tunable Graphene Oxide Interfaces.

Despite issues related to dendrite formation, research on Li metal anodes has resurged because of their high energy density. In this study, graphene oxide (GO) layers are decorated onto Li metal anodes through a simple process of drop-casting and spray-coating. The self-assembly of GO is exploited to synthesize coatings having compact, mesoporous, and macroporous morphologies. The abilities of the GO coatings to suppress dendrite formation are compared through Li|Li symmetrical cell charging at a current density of 5 mA cm-2 for 2000 cycles-a particularly abusive test. The macroporous structure possesses the lowest impedance, whereas the compact structure excels in terms of stability. Moreover, GO exhibits a low nucleation overpotential and is transformed into reduced GO with enhanced conductivity during the operation of the cells; both factors synergistically mitigate the issue of dendrite formation. Li-S batteries incorporating the GO-decorated Li anodes exhibit an initial capacity of 850 mA h g-1 and maintain their stability for 800 cycles at a C-rate of 1 C (1675 mA h g-1), suggesting the applicability of GO in future rechargeable batteries