Protic Amine Carboxylic Acid Ionic Liquids Additives Regulate α-FAPbI3 Phase Transition for High Efficiency Perovskite Solar Cells

The α-phase formamidinium lead tri-iodide (α-FAPbI₃) has become the most promising photovoltaic absorber for perovskite solar cells (PSCs) due to its outstanding semiconductor properties and astonishing high efficiency. However, the incomplete crystallization and phase transition of α-FAPbI₃ substantially undermine the performance and stability of PSCs. In this work, a series of the protic amine carboxylic acid ion liquids are introduced as the precursor additives to efficiently regulate the crystal growth and phase transition processes of α-FAPbI₃. The MA₂Pb₃I₈·2DMSO phase is inhibited in annealing process, which remarkably optimizes the phase transition process of α-FAPbI₃. It is noted that the functional groups of carboxyl and ammonium passivate the undercoordinated lead ions, halide vacancies, and organic vacancies, eliminating the deleterious nonradiative recombination. Consequently, the small-area devices incorporated with 2% methylammonium butyrate (MAB) and 1.5% n-butylammonium formate (BAFa) in perovskite show champion efficiencies of 25.10% and 24.52%, respectively. Furthermore, the large-area modules (5 cm × 5 cm) achieve PCEs of 21.26% and 19.27% for MAB and BAFa additives, indicating the great potential for commercializing large-area PSCs.     

α-CsPbI3 Bilayers via One-Step Deposition for Efficient and Stable All-Inorganic Perovskite Solar Cells

The emerging inorganic CsPbI₃ perovskites are promising wide-bandgap materials for application in tandem solar cells, but they tend to transit from a black α phase to a yellow δ phase in ambient conditions. Herein, a gradient grain-sized (GGS) CsPbI₃ bilayer is developed to stabilize the α phase via a single-step film deposition process. The spontaneously upward migration of (adamantan-1-yl)methanammonium (ADMA) based on the hot-casting technique causes self-assembly of the hierarchical morphology for the perovskite layers. Due to the strong steric effect of the surficial ADMA cation, a self-assembly tiny grain-sized CsPbI₃ layer is in situ formed at the surface site, which exhibits notably enhanced phase stability by its high surface energy. Meanwhile, a large grain-sized CsPbI₃ layer is obtained at the bottom site with high charge mobility and low trap density of states, which benefits from the regulated growth rates by the interaction between ADMA and perovskites. The perovskite solar cell (PSC) based on the GGS CsPbI₃ bilayer shows an efficiency of 15.5% and operates stably for 1000 h under ambient conditions. This work confirms that redistributing the surface energy of perovskite films is a facile strategy to stabilize metastable PSCs without the cost of efficiency loss.     

cPCN-Regulated SnO2 Composites Enables Perovskite Solar Cell with Efficiency Beyond 23％

Efficient electron transport layers(ETLs)not only play a crucial role in promoting carrier separation and electron extraction in perovskite solar cells(PSCs)but...     

Sputtering Deposition of Ultra-thin α-Fe_2O_3 Films for Solar Water Splitting

Ultra-thin α-Fe_2O_3(hematite) films have been deposited by radio frequency(RF) sputtering technique and photoelectrochemically investigated towards their ability to oxidize water.By varying the deposition power and time as well as the sputter gas flow(argon),the microstructure and morphology of the film were optimized.It was found that the increment in the film thickness resulted in the loss of efficiency for solar water oxidation.The film with a thickness of 27 nm exhibited the best result with a maximum photocurrent of 0.25 mA cm~(-2) at 1.23 V_(RHE).Addition of small amounts of O_2 to the sputter gas improved the photoactivity significantly.     

High-Quality Magnetically Hard ε-Fe2O3 Thin Films through Atomic Layer Deposition for Room-Temperature Applications

The critical-element-free ε-Fe₂O₃ ferrimagnet exhibits giant magnetic coercivity even at room temperature. It is thus highly attractive material for advanced applications in fields such as spintronics, high-density data storage, and wireless communication. However, a serious obstacle to overcome is the notoriously challenging synthesis of ε-Fe₂O₃ due to its metastable nature. Atomic layer deposition (ALD) is the state-of-the-art thin-film technology in microelectronics. Herein, it is demonstrated that it has also true potential for the fabrication of amazingly stable in situ crystalline and high-performance ε-Fe₂O₃ thin films from simple (FeCl₃ and H₂O) chemical precursors at a moderately low deposition temperature (280 °C). Standard X-ray diffraction and Fourier transfer infrared spectroscopy characterization indicates that the films are of high level of phase purity. Most importantly, precise temperature-dependent ⁵⁷Fe Mössbauer spectroscopy measurements verify that the hematite (α-Fe₂O₃) trace in the films is below 2.5%, and reveal the characteristic low- and high-temperature transitions at 208–228 K and ≈480 K, respectively, while magnetization measurements confirm the symmetric hysteresis loops expected for essentially phase-pure ε-Fe₂O₃ films. Excitingly, the highly c-axis oriented film growth, the overall film quality, and the unique magnetic properties remain the same, independently of the substrate material used.     

Secondary Anti-Solvent Treatment for Efficient 2D Dion–Jacobson Perovskite Solar Cells

Surface defects-mediated nonradiative recombination plays a critical role in the performance and stability of perovskite solar cells (PSCs) and surface post-treatment is widely used for efficient PSCs. However, the commonly used surface passivation strategies are one-off and the passivation defect ability is limited, which can only solve part of the defects in the topmost surface area. Here, a secondary anti-solvent strategy is proposed to further reduce surface defects based on conventional surface passivation for the first time. Based on this, the crystallization quality of 2D Dion–Jacobson perovskite is enhanced and the surface defects density is further reduced by nearly two orders. In addition, a gradient structure of perovskite with n = 2 phases located at the top of the film and 3D-like phases located at the bottom of the film can also be obtained. The modulated perovskite film boosts the efficiency of 2D perovskites (n = 5) up to 19.55%. This strategy is also very useful in other anti-solvent processed perovskite dipping systems, which paves a promising avenue for minimizing surface defects toward highly efficient perovskite devices.     

Combining Efficiency and Stability in Mixed Tin–Lead Perovskite Solar Cells by Capping Grains with an Ultrathin 2D Layer

The development of narrow-bandgap (E_g ≈ 1.2 eV) mixed tin–lead (Sn–Pb) halide perovskites enables all-perovskite tandem solar cells. Whereas pure-lead halide perovskite solar cells (PSCs) have advanced simultaneously in efficiency and stability, achieving this crucial combination remains a challenge in Sn–Pb PSCs. Here, Sn–Pb perovskite grains are anchored with ultrathin layered perovskites to overcome the efficiency-stability tradeoff. Defect passivation is achieved both on the perovskite film surface and at grain boundaries, an approach implemented by directly introducing phenethylammonium ligands in the antisolvent. This improves device operational stability and also avoids the excess formation of layered perovskites that would otherwise hinder charge transport. Sn–Pb PSCs with fill factors of 79% and a certified power conversion efficiency (PCE) of 18.95% are reported—among the highest for Sn–Pb PSCs. Using this approach, a 200-fold enhancement in device operating lifetime is achieved relative to the nonpassivated Sn–Pb PSCs under full AM1.5G illumination, and a 200 h diurnal operating time without efficiency drop is achieved under filtered AM1.5G illumination.     

Fully Roll-to-Roll Processed Efficient Perovskite Solar Cells via Precise Control on the Morphology of PbI2∶CsI Layer

Perovskite solar cells(PSCs)have attracted tremendous attention as a promising alternative candidate for clean energy genera-tion.Many attempts have been made w...     

A Special Additive Enables All Cations and Anions Passivation for Stable Perovskite Solar Cells with Efficiency over 23％

Passivating undercoordinated ions is an effective way to reduce the defect densities at the surface and grain boundaries (GBs) of perovskite materials for enhan...     

Up?Scalable Fabrication of -SnO2 with Multifunctional Interface for High Performance Perovskite Solar Modules

Tin dioxide -(SnO2) has been demonstrated as one of the promising electron transport layers for highefficiency perovskite solar cells (PSCs). However, scalable ...     

Synthesis of α-Mo_2C by Carburization of α-MoO_3 Nanowires and Its Electrocatalytic Activity towards Tri-iodide Reduction for Dye-Sensitized Solar Cells

Nanowire-shaped α-Mo O3 was synthesized on a large scale by hydrothermal route.Nanocrystalline α-Mo2 C phase was obtained by the carburization of α-Mo O3 nanowires with urea as a carbon source precursor.The phase purity and crystalline size of the synthesized materials were ascertained by using powder X-ray diffraction.The shape and morphology of synthesized materials were characterized by field-emission scanning electron microscopy(FE-SEM) and high resolution transmission electron microscopy(HR-TEM).The electrocatalytic activity of α-Mo2 C for I-/I3-redox couple was investigated by the cyclic voltammetry.The synthesized α-Mo2 C was subsequently applied as counter electrode in dye-sensitized solar cells to replace the expensive platinum.     

Atomic?Scale Layer?by?Layer Deposition of FeSiAl@ZnO@Al2O3 Hybrid with Threshold Anti?Corrosion and Ultra?High Microwave Absorption Properties in Low?Frequency Bands

Developing highly efficient magnetic microwave absorbers (MAs) is crucial, and yet challenging for anti-corrosion properties in extremely humid and salt-induced...     

Preparation of Double Perovskite Ca2NiWO6 as a Buffer Layer for YBa2Cu3O7−δ Coated Conductors

Ca₂NiWO₆ films were deposited on the Y-stabilized ZrO₂ (100) (YSZ) single crystalline substrates by pulsed laser deposition process. X-ray diffraction reveals that the Ca₂NiWO₆ film is coherently strained due to the small lattice mismatch between Ca₂NiWO₆ and YSZ substrate. With this c-axis orientated Ca₂NiWO₆ film as buffer layer, YBa₂Cu₃O_7?δ film has been successfully prepared by pulsed laser deposition. The subsequently deposited YBa₂Cu₃O_7?δ film has a preferred c-axis orientation and a smooth surface. The temperature dependence of resistance indicates a superconducting critical temperature higher than 82 K. Our results demonstrate that the double perovskite Ca₂NiWO₆ is a promising buffer layer candidate for coated conductors.     

Novel process for synthesis of α-Fe2O3: microstructural and optoelectronic investigations

Novel chemical synthesis method has been successfully employed for the preparation of n type α-Fe₂O₃ nanoparticles. Thin films of annealed Fe₂O₃ powders processed on glass substrates using spin coating technique. The effects of process temperature on the structural, morphological, electrical transport and optical properties were studied. X-ray diffraction study revealed formation of single phase nanocrystalline hexagonal α-Fe₂O₃. Microstructural analysis confirms nanostructured morphology. Dc electrical conductivity measurement reveled the semiconducting nature with room temperature electrical conductivity increased from 10^?4 to 10^?3 (Ω cm)^?1 as process temperature of Fe₂O₃ increased from 400 to 700 °C respectively. The n-type electrical conductivity is confirmed from thermo-emf measurement with no appreciable change in thermoelectric power after increasing processing temperature. The decrease in the band gap energy from 3.88 to 2.62 eV was observed after increasing process temperature.     

Organic-Salt-Assisted Crystal Growth and Orientation of Quasi-2D Ruddlesden–Popper Perovskites for Solar Cells with Efficiency over 19%

Quasi-2D Ruddlesden–Popper (RP) perovskite solar cells (PSCs) have drawn significant attention due to their appealing environmental stability compared to their 3D counterparts. However, the relatively low power conversion efficiency (PCE) greatly limits their applications. Here, high photovoltaic performance is demonstrated for quasi-2D RP PSCs using 2-thiophenemethylammonium as spacer with nominal n-value of 5, which is based on the stoichiometry of the precursors. The incorporation of formamidinium (FA) in quasi-2D RP perovskites reduces the bandgap and improves the light absorption ability, resulting in enlarged photocurrent and an increased PCE of 16.18%, which is higher than that of reported analogous methylammonium (MA)-based quasi-2D PSC (≈15%). A record high PCE of 19.06% is further demonstrated by using an organic salt, namely, 4-(trifluoromethyl)benzylammonium iodide, assisted crystal growth (OACG) technique, which can induce the crystal growth and orientation, tune the surface energy levels, and suppress the charge recombination losses. More importantly, the devices based on OACG-processed quasi-2D RP perovskites show remarkable environmental stability and thermal stability, for example, the PCE retaining ≈96% of its initial value after storage at 80 °C for 576 h, while only ≈37% of the original efficiency left for FAPbI₃-based 3D PSCs.     

Efficient Two‑Dimensional Perovskite Solar Cells Realized by Incorporation of Ti3C2Tx MXene as Nano‑Dopants

Two-dimensional(2D)perovskites solar cells(PSCs)have attracted considerable attention owing to their excellent stability against humidity;however,some imperfectness of 2D perovskites,such as poor crystallinity,disordered orientation,and inferior charge transport still limit the power conversion efficiency(PCE)of 2D PSCs.In this work,2D Ti3C2Tx MXene nanosheets with high electrical conductivity and mobility were employed as a nanosized additive to prepare 2D Ruddlesden–Popper perovskite films.The PCE of solar cells was increased from 13.69(without additive)to 15.71%after incorporating the Ti₃C₂T_x nanosheets with an optimized concentration.This improved performance is attributed to the enhanced crystallinity,orientation,and passivated trap states in the 3D phase that result in accelerated charge transfer process in vertical direction.More importantly,the unencapsulated cells exhibited excellent stability under ambient conditions with 55±5%relative humidity.     

Growth of Carbon Nanocoils by Porous α-Fe2O3/SnO2 Catalyst and Its Buckypaper for High Efficient Adsorption

High-purity(99%)carbon nanocoils(CNCs)have been synthesized by using porousα-Fe2O3/SnO2 catalyst.The yield of CNCs reaches 9,098%after a 6 h growth.This value is much higher than the previously reported data,indicating that this method is promising to synthesize high-purity CNCs on a large scale.It is considered that an appropriate proportion of Fe and Sn,proper particle size distribution,and a loose-porous aggregate structure of the catalyst are the key points to the high-purity growth of CNCs.Benefiting from the high-purity preparation,a CNC Buckypaper was successfully prepared and the electrical,mechanical,and electrochemical properties were investigated comprehensively.Furthermore,as one of the practical applications,the CNC Buckypaper was successfully utilized as an efficient adsorbent for the removal of methylene blue dye from wastewater with an adsorption efficiency of 90.9%.This study provides a facile and economical route for preparing high-purity CNCs,which is suitable for large-quantity production.Furthermore,the fabrication of macroscopic CNC Buckypaper provides promising alternative of adsorbent or other practical applications.     

Radiation Resistance of α-Si:H/Si Heterojunction Solar Cells with a Thin <Emphasis Type="Italic">i</Emphasis>-α-Si:H Inner Layer

We have studied the degradation of photoelectric characteristics of heterojunction solar cell samples based on α-Si:H/Si structures upon irradiation by electrons with an energy of 3.8 MeV and fluences of 1 × 10¹²–1 × 10¹⁴ cm^–2. It is shown that the efficiency of the samples of heterojunction solar cell elements under the conditions of AM0 illumination (0.136 W/cm²) is reduced by 25% at a fluence of 2 × 10¹³ cm^–2. This is more than an order of magnitude higher than the critical fluence value achieved previously when silicon solar cells with a p–n junction and an n-type base were irradiated by high-energy electrons.