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In this study, the optical behavior of lead‐free Bi‐based low‐dimensional perovskite single crystals (Cs3Bi2Cl9, Cs3Bi2Br9, Cs3Bi2I9, and MA3Bi2I9) is investigated by spectroscopic ellipsometry, supported by X‐ray diffraction and density functional theory calculations. All materials exhibit a strong excitonic peak resulting from photogenerated electron–hole Coulomb interactions, whereas the threshold of continuous absorption is found at higher energies. The resonances of the excitonic and continuous bands, along with exciton binding energies, are extracted through Critical Point Analysis of the ellipsometric data over a wide temperature range (from −90 °C to 90 °C), revealing subtle variations in the optical characteristics for each single crystal. These materials can be applied in optoelectronics as photodetectors because of their high stability and lower toxicity compared to their Pb‐based perovskites. [ABSTRACT FROM AUTHOR]

Hole‐transporting layer‐free mesoporous carbon (mC) architectures represent a printable, low‐cost, and stable solution for the future commercialization of perovskite solar cells (PSCs). CsPbI3 perovskite is attracting attention for its inorganic structure, which yields higher structural stability compared to hybrid counterparts and allows reversibility of its photoactive phase. Here the photovoltaic performance of large‐area (144 mm2) devices infiltrated with CsPbI3:EuCl3 is systematically evaluated, using AVA‐MAPbI3 mC‐PSCs as a reference. Measured and simulated J–V curves acquired at various scan rates show a significantly reduced hysteresis for Eu‐doped CsPbI3 with respect to AVA‐MAPbI3 mC‐PSCs. The synergic comparison between experiments and simulations reveals the complex interplay between ionic and electronic charges in the two mC‐PSCs, supporting the argument that cation migration is suppressed in CsPbI3:EuCl3. This also agrees with steady‐state photoconversion efficiency measured and simulated at fixed bias, which is constant over time in CsPbI3:EuCl3, contrary to what occurs in AVA‐MAPbI3 where a decay arises from enhanced ionic migration. In addition, CsPbI3:EuCl3 mC‐PSCs maintain their initial efficiency up to 250 h at 55 °C under continuous illumination during maximum power point tracking measurements. The possibility of reusing the CsPbI3:EuCl3 mC‐PSCs multiple times is demonstrated, pointing out the superiority of this inorganic perovskite in terms of sustainability. [ABSTRACT FROM AUTHOR]

In this study, we explore the potential of a blended material comprising CsPbI 3 : EuCl 3 perovskite and Gig-Lox TiO 2 , a unique transparent spongy material known for its multi-branched porous structure, for application in solar cells. The inclusion of EuCl 3 in CsPbI 3 serves to stabilize the photoactive γ -phase with a bandgap of 1.75 eV, making it suitable for solar energy conversion in tandem solar cells. Our study applies X-ray-based techniques to investigate the structural properties and interfacial behavior within this blended material, in comparison with a reference perovskite layer deposited on glass. In addition, Spectroscopic ellipsometry is complemented with density functional theory calculations and photoluminescence measurements to elucidate the absorption and radiative emission properties of the blend. Notably, our findings reveal a significant quenching of photoluminescence within the blended material, underscoring the pivotal role of the distributed interfaces in facilitating efficient carrier injection from the CsPbI 3 : EuCl 3 perovskite into the Gig-Lox TiO 2 sponge. These findings pave the way for the application of the blend as an Electron Transport Layer (ETL) in semi-transparent perovskite solar cells for tandem and building integrated photovoltaics. [ABSTRACT FROM AUTHOR]

Perovskite solar cells have become a popular alternative to traditional silicon solar cells due to their potential to provide high-efficiency, low-cost, and lightweight solar energy harvesting solutions. However, the multilayer architecture of perovskite solar cells demands careful investigation of the interaction and interfacing between the various layers, as they play a crucial role in determining the overall performance of the cell. In this context, the present work aims at analyzing the coupling between a spongy transparent electron-transporting layer (ETL) and perovskite in a formulation CsPbI 3 :EuI 2 . The ETL used in this work is a transparent mesoporous TiO 2 layer called "gig-lox" (grazing incidence angle geometry–local oxidation), which has been optimized to boost the interfacing with the perovskite for achieving a highly interconnected blend of materials. The gig-lox TiO 2 ETL shows a high surface wettability with respect to the perovskite solution, especially after pre-annealing at 500 ° C, and this enables the perovskite material to deeply infiltrate throughout it. The surface wettability of the gig-lox TiO 2 has been estimated by contact angle measurements, while the deep infiltration of the perovskite material has been demonstrated through X-ray diffraction and transmission electron microscopy analyses. Thanks to the achieved deep infiltration, the photo-generated charge injection from the perovskite into the mesoporous oxide is enhanced with respect to the use of a planar compact oxide, as shown by the photoluminescence measurements. The mainstay of the approach resides in the ETL that is deposited by a solvent-free sputtering method and is up-scalable for high industrial throughput. [ABSTRACT FROM AUTHOR]

The importance of lead analysis in environmental matrices becomes increasingly relevant due to the anthropogenic spread of toxic species in nature. Alongside the existing analytical methods to detect lead in a liquid environment, we propose a new dry approach for lead detection and measurement based on its capture from a liquid solution by a solid sponge and subsequent quantification based on X-ray analyses. The detection method exploits the relationship between the electronic density of the solid sponge, which depends on the captured lead, and the critical angle for total reflection of the X-rays. For this purpose, gig-lox TiO2 layers, grown by modified sputtering physical deposition, were implemented for their branched multi-porosity spongy structure that is ideal for capturing lead atoms or other metallic ionic species in a liquid environment. The gig-lox TiO2 layers grown on glass substrates were soaked into aqueous solutions containing different concentrations of Pb, dried after soaking, and finally probed through X-ray reflectivity analyses. It has been found that lead atoms are chemisorbed onto the many available surfaces within the gig-lox TiO2 sponge by establishing stable oxygen bonding. The infiltration of lead into the structure causes an increase in the overall electronic density of the layer and, thus, an increment of its critical angle. Based on the established linear relationship between the amount of lead adsorbed and the augmented critical angle, a standardized quantitative procedure to detect Pb is proposed. The method can be, in principle, applied to other capturing spongy oxides and toxic species. [ABSTRACT FROM AUTHOR]

Copper oxide thin films have been successfully synthesized through a metal–organic chemical vapor deposition (MOCVD) approach starting from the copper bis(2,2,6,6-tetramethyl-3,5-heptanedionate), Cu(tmhd)2, complex. Operative conditions of fabrication strongly affect both the composition and morphologies of the copper oxide thin films. The deposition temperature has been accurately monitored in order to stabilize and to produce, selectively and reproducibly, the two phases of cuprite Cu2O and/or tenorite CuO. The present approach has the advantages of being industrially appealing, reliable, and fast for the production of thin films over large areas with fine control of both composition and surface uniformity. Moreover, the methylammonium lead iodide (MAPI) active layer has been successfully deposited on the ITO/Cu2O substrate by the Low Vacuum Proximity Space Effusion (LV-PSE) technique. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM) analyses have been used to characterize the deposited films. The optical band gap (Eg), ranging from 1.99 to 2.41 eV, has been determined through UV-vis analysis, while the electrical measurements allowed to establish the p-type conductivity behavior of the deposited Cu2O thin films with resistivities from 31 to 83 Ω cm and carrier concentration in the order of 1.5–2.8 × 1016 cm−3. These results pave the way for potential applications of the present system as a hole transporting layer combined with a perovskite active layer in emergent solar cell technologies. [ABSTRACT FROM AUTHOR]

CsPbI3 perovskites are attracting huge interest for their inorganic structure and thanks to a bandgap of 1.69–1.78 eV that makes them suitable for application in tandem solar cells with silicon. Herein, all‐inorganic hole‐transporting‐layer (HTL)‐free carbon‐based CsPbI3 perovskite solar cells (mC‐PSCs) are fabricated, for the first time, by infiltrating CsPbI3 solutions enriched with precursors of Europium into triple mesoscopic structures with mesoporous (mp) materials (mp‐TiO2/mp‐ZrO2/mp‐Carbon). The use of Europium is beneficial to mitigate lattice defect formation during the reaction. Drop casting of the solution is done in air and the black γ‐phase formation is promoted under dynamic nitrogen flow during high‐temperature annealing (350 °C), which is preferred to low‐temperature treatments to maximize perovskite phase stability. The preparation protocol entrusts the devices with the best power conversion efficiencies (PCEs) of 9.2% and 5.2% using EuI2 and EuCl3, respectively. Recorded PCE is considerably lower (<2%) in the reference devices prepared without Europium. In addition, the Eu‐based devices are recycled to reconvert the photo‐inactive yellow δ‐phase into the photo‐active black γ‐phase with the devices losing only ≈10% of the efficiency of the original device. Thus, it is demonstrated that mC‐PSCs recycling is feasible by exploiting the special feature of the high‐temperature black γ‐phase‐reversibility. [ABSTRACT FROM AUTHOR]

The black γ‐phase of CsPbI3 with its bandgap at ≈1.75 eV can enable the take‐off of tandem solar cells as soon as intrinsic instability to the yellow δ‐phase is solved. Here, a black γ‐phase is formed at low temperature (80–90 °C) by incorporating Eu through EuCl3 or EuI2. It is forced to become yellow by thermal heating under nitrogen. It is demonstrated how spectroscopic ellipsometry and the related critical points analysis provide a new diagnostic tool to monitor the transformation through the bandgap footprint. As two sides of the same coin, the consumption of the black γ‐phase and the growth of the yellow δ‐phase are addressed and modeled in the range of 60–100 °C using the Avrami's theory. This approach allows extracting the activation energies of the phase transformation that are 0.95 eV versus 1.15 eV using EuI2 and EuCl3, respectively. In situ transmission electron microscopy analyses combined with fast marching simulations highlight that the phase transformation occurs through constant nucleation and growth. Europium has indeed the capability to tackle those processes and to extend the durability of the black γ‐phase at 30 °C in N2 to ≈250 days, hugely above the one observed without Eu (≈hours). [ABSTRACT FROM AUTHOR]

Investigations in the lower Colorado River Valley, Gulf Coastal Plain of Texas, have resulted in the development of a spatially and temporally controlled history of changes in channel and flood-plain erosional and depositional processes. When combined with paleo-climatic and stratigraphic data from the upper Colorado River drainage and the record of glacio-eustasy in the Gulf of Mexico, this study permits evaluation of the relative influence of different external controls on channel and flood-plain behavior, the development of alluvial landforms, and the development of alluvial stratigraphic sequences. Late Pleistocene and Holocene alluvial deposits of the lower Colorado River have been subdivided into allostratigraphic units, with chronological control afforded by radiocarbon ages. In the bedrock-confined valley, up to 10 m of late Pleistocene ([approximately] 20,000-14,000 yr B.P.) sediments referred to as the Eagle lake Alloformation (ELA) underlie a terrace at 17-20 m above the present-day channel. Deposition of the ELA was followed by bedrock valley incision, then deposition of a complex Holocene valley fill referred to as the Columbus Bend Alloformation (CBA). Columbus Bend Allomembers 1 and 2 (CBA-1 and CBA-2) underlie a terrace at 12-14 m above the present-day channel. CBA-1 was deposited [approximately] 12,000-5,000 yr B.P., whereas CBA-2 was deposited [approximately] 5,000-1,000 yr B.P. Columbus Bend Allomember 3 (CBA-3) consists of channel and flood-plain deposits that represent the past 600 yr of activity. Allostratigraphic units within the lower Colorado valley correlate with allostratigraphic units in major valley axes of the upper Colorado drainage and with records of climatic and environmental change, suggesting that alluvial deposits record basinwide responses to climatically controlled changes in discharge regimes and sediment supply. Basal unconformities for Holocene valley fills, however, appear to be 1,000-2,000 yr younger in the upper Colorado drainage than they are in the lower Colorado valley. This time-transgressive episode of bedrock valley cutting was initiated by climatically controlled reductions in sediment supply, but conditioned by limits on rates of upstream propagation of incision through a large drainage basin. By contrast, unconformities within Holocene valley fills document time-parallel episodes of flood-plain abandonment and soil formation, but little additional bedrock valley cutting, and indicate decreased flood magnitudes following shifts to drier climatic conditions. Flood-plain morphology and sedimentary facies changed through time in response to changes in climate coupled with a protracted degradation of upland soil mantles, which altered the rate at which precipitation was transferred to stream channels as runoff. During the late Pleistocene through middle Holocene, runoff was filtered through deep upland soils, floods were for the most part less flashy and contained within channel perimeters, and flood plains were constructed by lateral migration without significant vertical accretion; hence, the ELA and CBA-1 contain few vertical accretion facies. Exposure of bedrock surfaces during the late Holocene resulted in increased flood stages, deep overbank flooding, and construction of flood plains by vertical accretion; hence, CBA-2 and CBA-3 contain thick vertical accretion facies. Allostratigraphic units and bounding unconformities persist through the bedrock-confined valley to the Quaternary alluvial plain, but stratigraphic architecture changes substantially in the downstream direction as a result of the last glacio-eustatic cycle. On the alluvial plain, late Holocene CBA-2 and modern CBA-3, deposited contemporaneously with the present interglacial highstand, onlap and bury the ELA and CBA-1, which were emplaced during the last full glacial lowstand and the transgression that followed.

Halide perovskite solar cells can combine high photoconversion efficiency with high transmittance. Herein, we describe an innovative vacuum deposition method to prepare thin CH3NH3PbI3 (MAPbI3) layers for semitransparent perovskite solar cells. The method is based on two-step Low-Vacuum Proximity-Space-Effusion (LV-PSE: working pressure 2–4 × 10−2 mbar; source-substrate distance 1–3 cm) that guarantees high-quality at low production costs. The process parameter optimization was validated by theoretical calculation. We show that, during the process of CH3NH3I (MAI) deposition (second step) on PbI2 (first step) at a given substrate temperature, the conversion of the PbI2 film to MAPbI3 occurs from the top surface inward via an adsorption–incorporation–migration mechanism guided by the gradient of energetic MAI concentration. The quality of the final layer arises from this progressive conversion that also exploits the lattice order (texture) of the mother PbI2 layer. Finally, p–i–n solar cells were prepared using ITO/PTAA/MAPbI3/PCBM-BCP/Al architectures with a photo-active layer thickness of 150 nm. This layer, characterized by an Average Visible Transmittance (AVT) as high as 20%, produced an average efficiency of 14.4% that is a remarkable result considering the transparency vs. efficiency countertrend that indeed demands to boost the quality of the material. Very importantly, we demonstrated that a further down scalability of the MAPbI3 layer is feasible as proved by reducing the thickness down to 80 nm. In this specific case, the devices showed an average efficiency of 12.9% withstanding an AVT of 32.8%. This notable efficiency recorded on those extremely thin layers thus benefits from the exclusive quality of the MAPbI3 grown with the developed method. [ABSTRACT FROM AUTHOR]