Search Results (25)

In the recent reports, it is clear that lead-free perovskite materials with low band gaps are desirable candidates for photovoltaic cells. In this regard, it was observed that germanium (Ge) is a less toxic lead-free metal that is significant for the preparation of Ge-based perovskite materials. Ge-based perovskite materials, for example, methyl ammonium germanium iodide (MAGeI₃), cesium germanium iodide (CsGeI₃), and/or formamidinium germanium iodide (FAGeI₃) may be the suitable absorber materials and alternatives towards the fabrication of lead-free photovoltaic cells. In the past few years, few attempts were made to develop FAGeI₃-based perovskite solar cells, but their photovoltaic performance is still under limitations. This is indicating that some significant and effective strategies should be designed and developed for the construction of Ge-based perovskite solar cells. It is believed that optimization of layer thickness, device structure, and selection of a suitable electron transport layer (ETL) may improve the photovoltaic performance of FAGeI₃-based perovskite solar cells. Solar cell capacitance simulation, i.e., SCAPS is one of the promising software programs that can provide significant theoretical findings for the development of FAGeI_3-based perovskite solar cells. The simulation studies via SCAPS may benefit researchers to save their energy and high cost for the optimization process in the laboratories. In this research article, SCAPS was adopted as a simulation tool for the theoretical investigations of FAGeI_3-based perovskite solar cells. The simulation studies exhibited the excellent efficiency of 15.62% via SCAPS. This study proposed the optimized device structure of FTO/TiO₂/FAGeI₃/PTAA/Au with enhanced photovoltaic performance. Full article

In this study, a novel perovskite solar cell (PSC) architecture is presented that utilizes an HTL-free configuration with formamide tin iodide (FASnI₃) as the active layer and fullerene (C60) as the electron transport layer (ETL), which represents a pioneering approach within the field. The elimination of hole transport layers (HTLs) reduces complexity and cost in PSC heterojunction structures, resulting in a simplified and more cost-effective PSC structure. In this context, an HTL-free tin HC(NH₂)₂SnI₃-based PSC was simulated using the solar cell capacitance simulator (SCAPS) within a one-dimensional framework. Through this approach, the device performance of this novel HTL-free FASnI₃-based PSC structure was engineered and evaluated. Key performance parameters, including the open-circuit voltage (V_oc), short-circuit current density (J_sc), fill factor (FF), power conversion efficiency (PCE), I-V characteristics, and quantum efficiency (QE), were systematically assessed through the modulation of physical parameters across various layers of the device. A preliminary analysis indicated that the HTL-free configuration exhibited improved I-V characteristics, with a PCE increase of 1.93% over the HTL configuration due to improved electron and hole extraction characteristics, reduced current leakage at the back contact, and reduced trap-induced interfacial recombination. An additional boost to the device’s key performance parameters has been achieved through the further optimization of several physical parameters, such as active layer thickness, bulk and interface defects, ETL thickness, carrier concentration, and back-contact materials. For instance, increasing the thickness of the active layer PSC up to 1500 nm revealed enhanced PV performance parameters; however, further increases in thickness have resulted in performance saturation due to an increased rate of hole–electron recombination. Moreover, a comprehensive correlation study has been conducted to determine the optimum thickness and donor doping level for the C60-ETL layer in the range of 10–200 nm and 10¹²–10¹⁹ cm⁻³, respectively. Optimum device performance was observed at an ETL-C60 ultra-thin thickness of 10 nm and a carrier concentration of 10¹⁹ cm⁻³. To maintain improved PCEs, bulk and interface defects must be less than 10¹⁶ cm⁻³ and 10¹⁵ cm⁻³, respectively. Additional device performance improvement was achieved with a back-contact work function of 5 eV. The optimized HTL-free FASnI₃ structure demonstrated exceptional photovoltaic performance with a PCE of 19.63%, V_oc of 0.87 V, J_sc of 27.86 mA/cm², and FF of 81%. These findings highlight the potential for highly efficient photovoltaic (PV) technology solutions based on lead-free perovskite solar cell (PSC) structures that contribute to environmental remediation and cost-effectiveness. Full article

A new series of inorganic–organic hybrid perovskite materials were prepared by microwave-assisted grafting reactions. Simple carboxylic acids, acetic acid, and propionic acid, as well as hydroxyaromatic carboxylic acids, 3,5-dihydroxy benzoic acid (DBA), 5-hydroxyisophthalic acid (HPA), 4-hydroxybenzoic acid (HBA), and 4-hydroxy-4-biphenyl carboxylic acid (HBCA), were reacted with the Dion–Jacobson double-layered perovskite, HLaNb₂O_7, and its alcoxy derivatives. Grafting was found to not occur with simple carboxylic acids, while those molecules with hydroxyls were all attached to the perovskite interlayers. Reactivity of the hydroxyaromatic carboxylic acids varied with the different layered perovskite hosts where reactions with HLaNb₂O₇ did not occur, and those with n-propoxy-LaNb₂O₇ were limited; the greatest extent of reactivity was seen with n-decoxy-LaNb₂O₇. This is attributed to the larger interlayer spacing available for the insertion of the various hydroxyaromatic carboxylic acid compounds. The loading exhibited by the grafting species was less than that seen with well-known long-chain alkoxy grafting groups. It is expected that the width of the molecules contributes to this where, due to the benzyl groups, the interlayer volume of the grafted moieties occupies a larger horizontal fraction, therefore minimizing the loading to the below half. X-ray powder diffraction and transmission electron microscopy studies found that grafting of the n-decoxy-LaNb₂O₇ intermediates with the series of hydroxyaromatics resulted in a reduction in crystallinity along with a disruption of the layer structure. Raman data on the series show little variation in local structure except for HBCA, where there appears to be a lengthening of the Nb-O apical linkage and a possible reduction in the distortion of inner-layer NbO₆ octahedra. The optical properties of the hydroxyaromatic carboxylic acid grafted perovskites were also investigated using diffuse-reflectance UV-Vis spectroscopy. The band gaps of DBA, HPA, and HBA were found to be similar to the parent (E_g ≈ 3.4 eV), while the HBCA was significantly less by ca. 0.6 eV. This difference is attributed to electron withdrawal from the perovskite block to the HBCA ligand, leading to a lower band gap for the HBCA compound. The methods described herein allow for the formation of a new series of inorganic–organic hybrid materials where the products are of interest as precursors to more complex architectures as well as models for band gap modification of metal oxide photocatalysts. Full article

We investigate vibrations of the pyridinium cation PyH⁺ = C₅H₅NH⁺ in one-dimensional lead halide perovskites PyPbX₃ and pyridinium halide salts PyHX (X⁻ = I⁻, Br⁻), combining infrared absorption and Raman scattering methods at room temperature. Internal vibrations of the cation were assigned based on density functional theory modeling. Some of the vibrational bands are sensitive to perovskite or the salt environment in the solid state, while halide substitution has only a minor effect on them. These findings have been confirmed by ¹H, ¹³C and ²⁰⁷Pb solid-state nuclear magnetic resonance (NMR) experiments. Narrower vibrational bands in perovskites indicate less disorder in these materials. The splitting of NH-group vibrational bands in perovskites can be rationalized the presence of nonequivalent crystal sites for cations or by more exotic phenomena such as quantum tunneling transition between two molecular orientations. We have shown how organic cations in hybrid organic–inorganic crystals could be used as spectators of the crystalline environment that affects their internal vibrations. Full article

In this study, we have employed a film deposition technique based on convective forces acting at the triple air–solution–substrate contact line to tune the rate of solvent evaporation and, thus, to exert control over the morphology of the resulting mixed lead halide perovskite CH₃NH₃PbI_3-xCl_x films. By varying the speed of film deposition while processing at two different temperatures, perovskite crystals of various shapes and dimensions were generated upon the crystallization of the initial perovskite precursor ink. More precisely, longer than half a millimeter 3D needle-like perovskite crystals exhibiting sharp edges co-existing with large cross-like 3D perovskite crystals could only be obtained upon the slow deposition of films at a low sample processing temperature of 17 °C, i.e., under conditions of low solvent evaporation rate. On the contrary, the utilization of higher film deposition speeds and/or processing temperatures led to smaller 3D needle-like or quasi-2D rectangular perovskite crystals that often appeared interconnected and coalesced. Moreover, as it was revealed by the photoluminescence measurements, the emission intensity of perovskite crystals was larger and dominated by a shorter wavelength peak, as compared to the uncrystallized material that emitted much less light, but at a longer wavelength. Full article

The two-step sequential deposition is a commonly used method by researchers for fabricating perovskite solar cells (PSCs) due to its reproducibility and tolerant preparation conditions. However, the less-than-favorable diffusive processes in the preparation process often result in subpar crystalline quality in the perovskite films. In this study, we employed a simple strategy to regulate the crystallization process by lowering the temperature of the organic-cation precursor solutions. By doing so, we minimized interdiffusion processes between the organic cations and pre-deposited lead iodide (PbI₂) film under poor crystallization conditions. This allowed for a homogenous perovskite film with improved crystalline orientation when transferred to appropriate environmental conditions for annealing. As a result, a boosted power conversion efficiency (PCE) was achieved in PSCs tested for 0.1 cm² and 1 cm², with the former exhibiting a PCE of 24.10% and the latter of 21.56%, compared to control PSCs, which showed a PCE of 22.65% and 20.69%, respectively. Additionally, the strategy increased device stability, with the cells holding 95.8% and 89.4% of the initial efficiency even after 7000 h of aging under nitrogen or 20–30% relative humidity and 25 °C. This study highlights a promising low-temperature-treated (LT-treated) strategy compatible with other PSCs fabrication techniques, adding a new possibility for temperature regulation during crystallization. Full article

The commercialization of perovskite solar cells is hindered by the poor thermal stability of organic–inorganic hybrid perovskite materials. Herein, we demonstrate that crystalline thermoplastic polymer additives, such as a mixture of polyethylene oxide (PEO, 100,000 MW) and polyethylene glycol (PEG, 12,000 MW), can improve the thermal stability of CH₃NH₃PbI₃ (MAPbI₃) perovskites and thereby enhance device stability. High-quality less-defect perovskite films were obtained by establishing a strong reaction between hydroxy groups in the PEO + PEG mixture and the uncoordinated Pb²⁺ in MAPbI₃ perovskites, leading to a high power conversion efficiency of over 18% despite the presence of insulating thermoplastic polymers in the MAPbI₃ film. More importantly, as compared with pristine MAPbI₃ perovskite solar cells, the PEO + PEG-modified counterparts showed significantly improved stability under thermal treatment at 85 °C in ambient air with a relative humidity of 50–60%, remaining at nearly 71% of their initial efficiency values after 120 h. These demonstrations offer a feasible thermoplastic polymer additive engineering strategy to improve the thermal stability of perovskite solar cells. Full article

Methylammonium lead iodide (MAPbI₃) perovskite quantum dots (QDs) have become one of the most promising materials for optoelectronics. Understanding the dynamics of the charge transfer from MAPbI₃ QDs to the charge transport layer (CTL) is critical for improving the performance of MAPbI₃ QD photoelectronic devices. However, there is currently less consensus on this. In this study, we used an ultrafast transient absorption (TA) technique to investigate the dynamics of charge transfer from MAPbI₃ QDs to CTL titanium dioxide (TiO₂), elucidating the dependence of these kinetics on QD size with an injection rate from 1.6 × 10¹⁰ to 4.3 × 10¹⁰ s⁻¹. A QD solar cell based on MAPbI₃/TiO₂ junctions with a high-power conversion efficiency (PCE) of 11.03% was fabricated, indicating its great potential for application in high-performance solar cells. Full article

The technology of perovskite solar cells (PSC) is getting close to breaching the consumer market. Yet, one of the current challenges is to reduce the toxicity during their fabrication by reducing the use of the toxic solvents involved in the perovskite fabrication process. A good solubilization of lead halides used in hybrid perovskite preparation is required, and it is only possible with polar solvents. A mixture of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is the most popular solvent combination for a perovskite precursor solution. DMF is necessary to ensure a good dissolution of lead iodide, but it is also the most toxic solvent. In this paper, we study the replacement of the dimethylformamide with presumably less toxic alternatives, such as N-methyl-2-Pyrrolidone (NMP) and ethyl acetate (EA), for the preparation of the K_0.1FA_0.7MA_0.2PbI_2.8Cl_0.2 (KFAMA) hybrid perovskite. The perovskite thin films were investigated by various characterization techniques: X-ray diffraction, atomic force microscopy, scanning electron microscopy, and UV–vis spectroscopy, while the photovoltaic parameters were determined by measuring the IV curves of the corresponding solar cells. The present study shows that by keeping the same deposition parameters as when only DMF solvent is used, the partial solvent substitution with NMP and EA gives promising results for reducing the toxicity of the fabrication process of KFAMA-based PSCs. Thus, with no specific optimization of the deposition process, and for the maximum possible partial substitution of DMF with NMP and EA solvents, the loss in the power conversion efficiency (PCE) value is only 35% and 18%, respectively, associated with the more structural defects promoted by NMP and EA. Full article

The double perovskite halides A₂B^IB^IIIX₆ provide flexibility for various formulation adjustments and are of less toxicity in comparison with well-discussed complex lead halide derivatives. Such type of structure can be formed by replacing two Pb²⁺ ions in the cubic lattice with a pair of non-toxic heterovalent (monovalent and trivalent) metal cations, such as silver and indium. The aim of this work is to briefly characterize the phase equilibria in the ternary system CsBr-AgBr-InBr₃ and investigate the thermodynamic availability of synthesis of Cs₂AgInBr₆ double perovskite phase by solid-state sintering or melt crystallization. The results demonstrate the unfeasibility of the Cs₂AgInBr₆ phase but high stability of the corresponding binary bromides perspective for optoelectronics. Full article

Recently, the design and fabrication of lead (Pb)-free perovskite or perovskite-like materials have received great interest for the development of perovskite solar cells (PSCs). Manganese (Mn) is a less toxic element, which may be an alternative to Pb. In this work, we explored the role of NH₃(CH₂)₂NH₃MnCl₄ perovskite as a light absorber layer via SCAPS-1D. A Pb-free PSC device (FTO/TiO₂/NH₃(CH₂)₂NH₃MnCl₄/spiro-OMeTAD/Au) was simulated via SCAPS-1D software. The simulated Pb-free PSCs (FTO/TiO₂/NH₃(CH₂)₂NH₃MnCl₄/spiro-OMeTAD/Au) showed decent power conversion efficiency (PCE) of 20.19%. Further, the impact of the thickness of absorber (NH₃(CH₂)₂NH₃MnCl₄), electron transport (TiO₂), and hole-transport (spiro-OMeTAD) layers were also investigated. Subsequently, various electron transport layers (ETLs) were also introduced to investigate the role of ETL. In further studies, an NH₃(CH₂)₂NH₃MnCl₄-based PSC device (FTO/TiO₂/NH₃(CH₂)₂NH₃MnCl₄/spiro-OMeTAD/Au) was also developed (humidity = ~30–40%). The fabricated PSCs displayed an open circuit voltage (Voc) of 510 mV with a PCE of 0.12%. Full article

Changes in physical properties of (H₂C=C(CH₃)CO₂CH₂CH₂NH₃)₂PbI₂Cl₂ and (H₂C=C(CH₃)CO₂CH₂CH₂NH₃)₂Pb(NO₃)₂Cl₂ (2D) perovskite materials from iodide-based (I-AMP) and nitrate-based (N-AMP) leads were investigated at different durations (days) for various storage conditions. UV-Vis spectra of both samples showed an absorption band of around λ_max 420 nm due to the transition of n to π* of ethylene (C=C) and amine (NH₂). XRD perovskite peaks could be observed at approximately 25.35° (I-AMP) and 23.1° (N-AMP). However, a major shift in I-AMP and dramatic changes in the crystallite size, FHWM and crystallinity percentage highlighted the instability of the iodide-based material. In contrast, N-AMP showed superior stability with 96.76% crystallinity even at D20 under the S condition. Both materials were exposed to ammonia (NH₃) gas, and a new XRD peak of ammonium lead iodide (NH₄PbI₃) with a red-shifted perovskite peak (101) was observed for the case of I-AMP. Based on the FWHM, crystallite size, crystallinity and lattice strain analysis, it can be concluded N-AMP’s stability was maintained even after a few days of exposure to the said gases. These novel nitrate-based lead perovskite materials exhibited great potential for stable perovskite 2D materials and recorded less toxicity compared to famous lead iodide (PbI₂) material. Full article

Perovskite-type oxides are highly flexible materials that show properties that are beneficial for application in reverse water-gas shift processes (rWGS). Due to their stable nature, the ability to incorporate catalytically active dopants in their lattice structure, and the corresponding feature of nanoparticle exsolution, they are promising candidates for a materials design approach. On an industrial level, the rWGS has proven to be an excellent choice for the efficient utilisation of CO₂ as an abundant and renewable carbon source, reflected by the current research on novel and improved catalyst materials. In the current study, a correlation between rWGS reaction environments (CO₂ to H₂ ratios and temperature), surface morphology, and catalytic activity of three perovskite catalysts (Nd_0.6Ca_0.4Fe_0.9Co_0.1O_3-δ, Nd_0.6Ca_0.4Fe_0.97Co_0.03O_3-δ, and Nd_0.6Ca_0.4Fe_0.97Ni_0.03O_3-δ) is investigated, combining catalytic measurements with SEM and NAP-XPS. The materials were found to react dynamically to the conditions showing both activation due to in situ nanoparticle exsolution and deactivation via CaCO₃ formation. This phenomenon could be influenced by choice of material and conditions: less reductive conditions (larger CO₂ to H₂ or lower temperature) lead to smaller exsolved particles and reduced carbonate formation. However, the B-site doping was also important; only with 10% Co-doping, a predominant activation could be achieved. Full article

Nowadays, Mn-doping is considered as a promising dissolution for the heavy usage of toxic lead in CsPbX₃ perovskite material. Interestingly, Mn-doping also introduces an additional photoluminescence band, which is favorable to enrich the emission gamut of this cesium lead halide. Here, a solution spraying strategy was employed for the direct preparation of CsPb_xMn_1−x(Br,Cl)₃ film through MnCl₂ doping in host CsPbBr₃ material. The possible fabrication mechanism of the provided approach and the dependences of material properties on Mn-doping were investigated in detail. As the results shown, Pb was partially substituted by Mn as expected. With the ratio of PbBr₂:MnCl₂ increasing from 3:0 to 1:1, the obtained film separately featured green, cyan, orange-red and pink-red emission, which was caused by the energy transferring process. Moreover, the combining energy of Cs, Pb, and Mn gradually red-shifted resulted from the formation of Cs-Cl, Pb-Cl and Mn-Br coordination bonding as MnCl₂ doping increased. In addition, the weight of short decay lifetime of prepared samples increased with the doping rising, which indicated a better exciton emission and less defect-related transition. The aiming of current work is to provide a new possibility for the facile preparation of Mn-doping CsPbX₃ film material. Full article

We show how sintering in different atmospheres affects the structural, microstructural, and functional properties of ~30 μm thick films of K_0.5Na_0.5NbO₃ (KNN) modified with 0.38 mol% K_5.4Cu_1.3Ta₁₀O₂₉ and 1 mol% CuO. The films were screen printed on platinized alumina substrates and sintered at 1100 °C in oxygen or in air with or without the packing powder (PP). The films have a preferential crystallographic orientation of the monoclinic perovskite phase in the [100] and [−101] directions. Sintering in the presence of PP contributes to obtaining phase-pure films, which is not the case for the films sintered without any PP notwithstanding the sintering atmosphere. The latter group is characterized by a slightly finer grain size, from 0.1 μm to ~2 μm, and lower porosity, ~6% compared with ~13%. Using piezoresponse force microscopy (PFM) and electron backscatter diffraction (EBSD) analysis of oxygen-sintered films, we found that the perovskite grains are composed of multiple domains which are preferentially oriented. Thick films sintered in oxygen exhibit a piezoelectric d₃₃ coefficient of 64 pm/V and an effective thickness coupling coefficient k_t of 43%, as well as very low mechanical losses of less than 0.5%, making them promising candidates for lead-free piezoelectric energy harvesting applications. Full article