Synergic use of two-dimensional materials to tailor interfaces in large area perovskite modules

In the field of halide perovskite solar cells (PSCs), interface engineering has been conceptualized and exploited as a powerful mean to improve solar cell performance, stability, and scalability. In this regard, here we propose the use of a multi two-dimensional (2D) materials as intra and inter layers in a mesoscopic PSCs. By combining graphene into both compact and mesoporous TiO2, Ti3C2Tx MXenes into the perovskite absorbing layer and functionalized-MoS2 at the interface between perovskite and the hole transporting layer, we boost the efficiency of PSCs (i.e., +10%) compared to the 2D materials-free PSCs. The optimized 2D materials-based structure has been successfully extended from lab-scale cell dimensions to large area module on 121 cm2 substrates (11 x11 cm2) till to 210 cm2 substrates (14.5 x14.5 cm2) with active area efficiency of 17.2% and 14.7%, respectively. The remarkable results are supported by a systematic statistical analysis, testifying the effectiveness of 2D materials interface engineering also on large area devices, extending the 2D materials-perovskite photovoltaic technology to the industrial exploitation

Mixed cation halide perovskite under environmental and physical stress

Despite the ideal performance demonstrated by mixed perovskite materials when used as active layers in photovoltaic devices, the factor which still hampers their use in real life remains the poor stability of their physico-chemical and functional properties when submitted to prolonged permanence in atmosphere, exposure to light and/or to moderately high temperature. We used high resolution photoelectron spectroscopy to compare the chemical state of triple cation, double halide Cs-x(FA(0.83)MA(0.17))(()Pb-1-(x))(I0.83Br0.17)(3) perovskite thin films being freshly deposited or kept for one month in the dark or in the light in environmental conditions. Important deviations from the nominal composition were found in the samples aged in the dark, which, however, did not show evident signs of oxidation and basically preserved their own electronic structures. Ageing in the light determined a dramatic material deterioration with heavily perturbed chemical composition also due to reactions of the perovskite components with surface contaminants, promoted by the exposure to visible radiation. We also investigated the implications that 2D MXene flakes, recently identified as effective perovskite additive to improve solar cell efficiency, might have on the labile resilience of the material to external agents. Our results exclude any deleterious MXene influence on the perovskite stability and, actually, might evidence a mild stabilizing effect for the fresh samples, which, if doped, exhibited a lower deviation from the expected stoichiometry with respect to the undoped sample. The evolution of the undoped perovskites under thermal stress was studied by heating the samples in UHV while monitoring in real time, simultaneously, the behaviour of four representative material elements. Moreover, we could reveal the occurrence of fast changes induced in the fresh material by the photon beam as well as the enhanced decomposition triggered by the concurrent X-ray irradiation and thermal heating

Highly efficient 2D materials engineered perovskite/Si tandem bifacial cells beyond 29%

Perovskite/Silicon tandem technology represents a promising route to achieve 30% power conversion efficiency (PCE), by ensuring low levelized costs energy. In this article, we develop a mechanically stacked 2T perovskite/silicon tandem solar cell, with subcells independently fabricated, optimized, and subsequently coupled by contacting the back electrode of the mesoscopic perovskite top cell with the texturized and metalized front contact of the silicon bottom cell. The possibility to separately optimize the two sub-cells allows to carefully choose the most promising device structure for both top and bottom cells. Indeed, semitransparent perovskite top cell performance is boosted through the use of selected two-dimensional materials to tune the device interfaces. In addition, a protective buffer layer is used to prevent damages induced by the transparent electrode sputtering deposition over the hole transporting layer. A textured amorphous/crystalline silicon heterojunction cell fabricated with a fully industrial in-line production process is here used as state of art bottom cell. The perovskite/c-Si tandem device demonstrates remarkable PCE of 28.7%. Moreover, we demonstrate the use of a bifacial silicon bottom cell, as a viable way for overcoming the current matching constrain imposed by the 2T configuration. Here, the current generation difference between perovskite and c-Si cells is compensated by exploiting the albedo radiation thanks to the bifaciality of the commercial c-Si cell used in this article. Considering standard rear irradiation, final power generation density above 32 mW/cm(2) can be achieved, paving the way for a tandem technology customable according to the final installation site

Complex Study of Magnetization Reversal Mechanisms of FeNi/FeMn Bilayers Depending on Growth Conditions

Magnetization reversal processes in the NiFe/FeMn exchange biased structures with various antiferromagnetic layer thicknesses (0–50 nm) and glass substrate temperatures (17–600◦C) during deposition were investigated in detail. Magnetic measurements were performed in the temperature range from 80 K up to 300 K. Hysteresis loop asymmetry was found at temperatures lower than 150 K for the samples with an antiferromagnetic layer thickness of more than 10 nm. The average grain size of FeMn was found to increase with the AFM layer increase, and to decrease with the substrate temperature increase. Hysteresis loop asymmetry was explained in terms of the exchange spring model in the antiferromagnetic layer. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Ministry of Education and Science of the Russian Federation, Minobrnauka: FEUZ-2020-0051; Agentúra na Podporu Výskumu a Vývoja, APVV: APVV-20-0324Funding: This work has been supported by the grant of the Slovak Research and Development Agency under the contract No APVV-20-0324. This work was in part financially supported by the Ministry of Science and Higher Education of the Russian Federation, Subject of the state task No. FEUZ-2020-0051. The electron microscopy investigations were carried out on the equipment of Krasnoyarsk Regional Center of Research Equipment of Federal Research Center «Krasnoyarsk Science Center SB RAS»

Electronic Structure Sensitivity to Surface Disorder and Nanometer-Scale Impurity of 2D Titanium Carbide MXene Sheets as Revealed by Electron Energy-Loss Spectroscopy

International audienceTwo-dimensional (2D) carbides and/or nitrides (so-called MXenes) are among the latest and largest family of 2D materials. Due to their 2D nature and their unique properties of hydrophilicity, good metallic conductivity, and structural diversity, these materials are intensively studied for sensing applications or as supports for nanomaterials toward, e.g., plasmonics, catalytic, or energy storage applications. For these potential usages, the extent to which the electronic properties of MXene sheets are modified upon functionalization or intercalation is critical, and an optimized nondestructive probing of the interaction between MXene layers and functionalization is important to be determined. Here, these issues are addressed using a combination of first-principles simulations and electron energy loss spectroscopy (EELS) experiments performed at the nanoscale on Ti3C2Tx and Ti2CTx MXene multilayers, where T denotes the surface functionalization groups. Based on a detailed analysis of the carbon and surface group K edge fine structure, we show that the C-K edge is an ideal marker for surface-induced electronic structure modifications in the Tin+1Cn conducting core. These results highlight how a nanometer-scale impurity can very locally interact with a Ti3C2Tx multilayer and modify its electronic structure. This approach allows discrimination between the surface and core alteration of the Ti3C2Tx layers. Finally, the higher sensitivity to surface states of the Tin+1Cn conducting core in Ti2CTx as compared to Ti3C2Tx is discussed. We expect these results to offer an approach for understanding MXenes’ behavior and especially characterize their interactions with other nanomaterials when used in composite

Decoration of laser induced graphene with MXene and manganese oxide for fabrication of a hybrid supercapacitor

During the last years, Internet of Things has become a prominent topic of technical, social, and economic importance. One of the main consequences is the high demand for energy and power density from small energy storage devices. In this field the laser induced graphene (LIG) has become a promising material to produce flexible micro-supercapacitors. The issue with this material is that the performances are strongly restrained by its limited surface area and the relatively low conductivity. In this work we improve the performance of a LIG supercapacitor by decorating its surface through electrophoresis: one electrode will be decorated with metal nitrides and metal carbides (MXenes), the other with manganese oxide. These two materials have appreciable conductivity and pseudocapacitance. Electrochemical measurements have been carried out on the two electrodes separately. After a charge balancing, the device has been sealed in pouch and tested

High-performance novel asymmetric MXene@CNT//N-doped CNT flexible hybrid device with large working voltage for energy storage

We developed a novel fiber-shaped supercapacitor based on a hybrid MXene@CNT//N-doped CNT device. In particular, for the first time, electrophoretically deposited Ti3C2Tx MXenes on carbon nanotube yarns and microwave-assisted nitrogen-doped carbon nanotube yarns are proposed as negative and positive electrodes, respectively. Short-circuit encountered during cell assembly was prevented entirely by coating a reproducible polyvinylidene difluoride (PVDF) membrane directly on the electrodes. Based on the developed electrodes, the assembled cell exhibited a large operating voltage window of up to 2.0 V in a diluted 0.5 M H2SO4 liquid electrolyte. The device displayed excellent stability over 5000 cycles with a Coulombic efficiency of nearly 100 %. The device withstood a floating test for 70 h with approximately 100 % capacity retention and exhibited excellent resistance to mechanical stress. Areal energy density as high as 298.5 mu Wh cm-2 was recorded for a power density value of 855.5 mu W.cm- 2 at an areal current value of 0.5 mA cm-2. At a high current density of 10 mA cm-2, the energy density remained high at 99.0 mu Wh cm-2 for a corresponding power density of 8.11 mW cm-2. The reported values rank among the highest obtained for carbon nanotubes-based wired-shaped super -capacitors and show the potential of this flexible wired-shaped hybrid energy storage unit as a wearable device