Unlocking photocatalytic potential: this review explores the remarkable properties of lead-free double halide perovskites, their synthesis methods, and their role in photocatalytic H 2 production and CO 2 reduction.

Halide perovskites (HPs) can be the effective functional materials for the sneak‐path current issue in the memristive crossbar array. Herein, an efficient strategy is proposed to integrate the HPs‐based bidirectional threshold and bipolar resistive switches (TS and RS). The resistance change characteristics from volatile threshold to nonvolatile resistive switching are modulated by controlling Ag doping concentration in the MAPbI3. HPs provide the diffusive condition and the quantity of Ag regulates the radius of its network. A low amount of Ag contributes to weak network with a short lifetime. However, when the amount of Ag increases, the conductive filament becomes more robust, showing a long lifetime. A MAPbI3:Ag TS with a low Ag content is developed, showing a steep switching slope (1 mV per decade), fast switching speed (< 80 ns), and low off‐current (10 nA). And, a MAPbI3:Ag RS with a high Ag content is developed, showing multilevel storage capability and long retention time (1400 s). Finally, these TS and RS coupled into the 1S‐1R integrated component, resulting the development of the maximum crossbar array size to 1.4 × 1012. This study offers an efficient methodology for tailoring the resistance change characteristics and a promising strategy for practical HPs‐based memristive crossbar application.

Interfacial engineering is extensively used to reduce the interfacial loss caused by surface recombination, improve the crystallinity of the active absorption layer, and enhance the long‐term stability of perovskite solar cells (PSCs). Solution processing techniques, such as spin coating and dip coating, are commonly used to deposit the interfacial layer because of their cost‐effectiveness and simplicity. Although determining suitable solutes for use in these processes is important, selecting appropriate solvents is also crucial. Herein, commonly used solvents are investigated to determine optimal solvents for solution processing by categorizing them into nonpolar and polar groups. The results suggest that the efficiency of the PSCs can be increased by simple solvent treatment. In particular, the efficiencies of systems subjected to hexane (nonpolar) and ethanol (polar) treatment are significantly improved (17.31% and 17.44%, respectively) compared with that of a control device (16.24%). Herein, the effects of pure solvents on the SnO2–perovskite interface are confirmed and an important direction for investigations that adopt solution processing to improve the efficiency of PSCs, such as research on interlayers and self‐assembled monolayers, is suggested.

In this study, the thermal stability of mixed-halide CsPb(BrxI1-x)(3) perovskite quantum dots was investigated by monitoring its absorption, photoluminescence spectra, and X-ray diffraction. CsPb(Br0.8I0.2)(3) was found to be the most stable composition at a constant temperature of 100 degrees C for up to 96 h, although some agglomeration was observed. In contrast, CsPb(Br0.2I0.8)(3) revealed the most unstable composition under the same conditions as the aggregated iodide-rich domain easily transformed into the yellow-colored, non-luminescent delta-phase. CsPb(Br0.5I0.5)(3) also showed phase segregation, where its original phase separated into bromide-rich and iodide-rich domains. By passivating the surface of mixed-halide perovskite, the particle agglomeration of CsPb(Br0.8I0.2)(3) and phase segregation of CsPb(Br0.5I0.5)(3) were significantly suppressed; however, the prevention of CsPb(Br0.2I0.8)(3) phase transformation was less successful.

In this study, halide perovskite nanocrystals are synthesized by controlling the ligand length and amount, and investigated the effects on the change in the ligand length and amount on the shape, size, crystal structure, and optical properties of the perovskite nanocrystals. The results reveal the tendency and respective effects of amine and acid ligands on perovskite nanocrystals. The amine ligands bind directly to the perovskite nanocrystals. Consequently, the amine ligands with longer chains interfere with the aggregation of the initially formed nanocrystals, thus limiting the size of the halide perovskite nanocrystals. Similar to the amine ligands, the acid ligands directly bond with the perovskite nanocrystals; however, they are also indirectly distributed around the nanocrystals, thus affecting their structure and dispersion. Consequently, the acid ligands affect the assembly of the initially formed nanocrystals, which determine the shape and crystal structure of the nanocrystals. It is believed that the report will provide useful insight on the synthesis of halide perovskites for application in optoelectronic devices.

CsPbI3 perovskite quantum dots (QDs) are more unstable over time as compared to other perovskite QDs, owing to ligand loss and phase transformation. The strong red emission from fresh CsPbI3 QDs gradually declines to a weak emission from aged QDs, which PLQY dropped by 93% after a 20 day storage; finally, there is no emission from delta-phase CsPbI3. The present study demonstrated a facile surface treatment method, where a sulfur-oleylamine (S-OLA) complex was utilized to passivate the defect-rich surface of the CsPbI3 QDs and then self-assembly to form a matrix outside the CsPbI3 QDs protected the QDs from environmental moisture and solar irradiation. The PLQY of the treated CsPbI3 QDs increased to 82.4% compared to initial value of 52.3% of the fresh QDs. Furthermore, there was a significant increase in the colloidal stability of the CsPbI3 QDs. Above 80% of the original PLQY of the treated QDs was reserved after a 20 day storage and the black phase could be maintained for three months before transforming to the yellow phase. The introduction of S-OLA induced the recovery of the lost photoluminescence of the nonluminous aged CsPbI3 QDs with time to 95% of that of the fresh QDs. Furthermore, the photoluminescence was maintained for one month. The increase in the stability and photoluminescence are critical for realizing high-performance perovskite-QD-based devices. Therefore, this work paves the way for increasing the performance of perovskite-based devices in the near future.

Perovskite solar cells (PSCs) have a high efficiency, and their price is relatively low; thus, they are attracting considerable attention as a substitute for expensive Si solar cells. However, highly efficient PSCs are not ecofriendly, because they contain toxic metals such as Pb. Therefore, we develop Sn-based PSCs to reduce the Pb content. First, 11 different perovskite precursors are synthesized by increasing the amount of Pb(SCN)(2) from 0 to 0.5 M in CH(NH2)(2)SnI3. Then, PSCs are fabricated, and their characteristics are compared. Scanning electron microscopy confirms that the proper amount of Pb(SCN)(2) uniformizes the grain size of the perovskite layer and reduces the amounts of pinholes. The crystallization and optical absorption of each pemvskite layer are confirmed by X-ray diffraction analysis and ultraviolet-visible spectra, and the characteristics of the PSCs are confirmed by the current density-voltage graph. The Sn-based PSCs with 0.25 M Pb(SCN)(2) exhibit a high efficiency of 8.4%, which is significantly higher than that (1.6%) of Sn-based PSCs without Pb(SCN)(2). The calculated Pb concentration of CH3NH3PbI3 is 0.37 g/mL, while that of CH(NH2)(2)SnI3 containing Pb(SCN)(2) is 0.08 g/mL. These results indicate the possibility of producing highly efficient PSCs with reduced lead content.

Metal-organic frameworks (MOFs) and MOF-derived materials have been used for several applications, such as hydrogen storage and separation, catalysis, and drug delivery, owing to them having a significantly large surface area and open pore structure. In recent years, MOFs have also been applied to thin-film solar cells, and attractive results have been obtained. In perovskite solar cells (PSCs), the MOF materials are used in the form of an additive for electron and hole transport layers, interlayer, and hybrid perovskite/MOF. MOFs have the potential to be used as a material for obtaining PSCs with high efficiency and stability. In this study, we briefly explain the synthesis of MOFs and the performance of organic and dye-sensitized solar cells with MOFs. Furthermore, we provide a detailed overview on the performance of the most recently reported PSCs using MOFs.

Planar perovskite solar cells were fabricated on F-doped SnO2 (FTO) coated glass substrates, with 4,4’-((1E,1’E)-((1,2,4-thiadiazole-3,5-diyl)bis(azaneylylidene))bis(methaneylylidene))bis(N,N-di-p-tolylaniline) (bTAThDaz) as hole transport material. This imine was synthesized in one step reaction, starting from commercially available and relatively inexpensive reagents. Electrochemical, optical, electrical, thermal and structural studies including thermal images and current-voltage measurements of the full solar cell devices characterize the imine in details. HOMO-LUMO of bTAThDaz were investigated by cyclic voltammetry (CV) and energy-resolved electrochemical impedance spectroscopy (ER-EIS) and were found at −5.19 eV and −2.52 eV (CV) and at −5.5 eV and −2.3 eV (ER-EIS). The imine exhibited 5% weight loss at 156 °C. The electrical behavior and photovoltaic performance of the perovskite solar cell was examined for FTO/TiO2/perovskite/bTAThDaz/Ag device architecture. Constructed devices exhibited good time and air stability together with quite small effect of hysteresis. The observed solar conversion efficiency was 14.4%.

This study reports an effective method to enhance the performance of photoelectrochemical (PEC) solar water reduction. We design and prepare a SnO2@RWS2 NF heterostructure on p-Si that has better visible-light absorption as well as low recombination of electron hole pairs. Consequently, a 3.5 mA cm(-2) photocurrent density at 0 V versus a reversible hydrogen electrode is obtained using SnO2@WS2, and bare SnO2 and WS2 photocathodes exhibit values of -0.6 and -0.36 mA cm(-2), respectively, showing the combined effects of these two materials for excellent hydrogen evolution reaction performance. Additionally, the photo current stability of the sample reveals the improved efficiency for the separation of generated charge carriers. Our study provides experimental and theoretical evidence that SnO2 doping improves the properties of WS2 for efficient PEC solar water reduction.

This study reports an effective method to enhance the performance of photoelectrochemical (PEC) solar water reduction. We design and prepare a SnO₂@WS₂ NF heterostructure on p-Si that has better visible-light absorption as well as low recombination of electron–hole pairs. Consequently, a −3.5 mA cm–² photocurrent density at 0 V versus a reversible hydrogen electrode is obtained using SnO₂@WS₂, and bare SnO₂ and WS₂ photocathodes exhibit values of −0.6 and −0.36 mA cm–², respectively, showing the combined effects of these two materials for excellent hydrogen evolution reaction performance. Additionally, the photocurrent stability of the sample reveals the improved efficiency for the separation of generated charge carriers. Our study provides experimental and theoretical evidence that SnO₂ doping improves the properties of WS₂ for efficient PEC solar water reduction.

The role of additives in the performance of CsPbI3 perovskite solar cells (PSCs) was investigated. Different kinds of cations and anions were used as additives in a N,N-dimethylformamide (DMF) solution containing CsI and PbI2 (1:1 molar ratio). These include HI, HBr, HCI, NH4I, NH4Br, and NH4CI. Additive cations (H+ and NH4+) as well as halide ions (I-, Br-, and Cl-) are important for the properties of PSCs. Especially, the addition of iodine ion showed good characteristics compared to Br- and Cl-. Among the CsPbI3 layers prepared with different kinds of additives and annealed at different temperatures, the X-ray diffraction peaks of CsPbI3 were clearly found at 14 degrees and 28 degrees for the sample annealed at 150 degrees C with 50 mu L of HI, suggesting the formation of a cubic structure at the low temperature of 150 degrees C. The field emission scanning electron microscopy images indicate that the surface of the perovskite layer with hydrogen halide additive ("H+"-based additive) is more uniform than that with ammonium additive. The roughness profiles determined by atomic force microscopy indicate that the CsPbI3 film with HI additive shows the least roughness among the samples with H+-based additives. Therefore, the best power conversion efficiency (PCE) of 4.72% is obtained for CsPbI3 PSCs annealed at 150 degrees C with HI (50 mu L). The H+-based additives seem to react with PbI2 in DMF solution, increasing the solubility of PbI2 and thus lowering the processing temperature. Furthermore, the PCE of CH3NH3PbI3-xClx PSCs decreased from 7.45 to 0.23%, whereas that of CsPbI3 PSCs with 50 mu L of HI only decreased from 3.55 to 2.78% after exposing the samples to air for 3 h. These results indicate that H+-based additives, especially HI, have more impact on the CsPbI3 PSCs in terms of lowering the processing temperature and improving the performance.

CH3NH3PbI3-xClx species were fabricated as light-absorbing layers for perovskite solar cells (PSCs), by employing NH4I, NH4Br, and NH4Cl as additives via annealing at 100 °C for different times. Solutions containing CH3NH3I, PbI2, and PbCl2 (4:1:1 molar ratio) in N,N-dimethylformamide were used to prepare perovskites with NH4I, NH4Br, and NH4Cl as additives, at concentrations of 0.1 M and 0.3 M. The additives helped increase the grain size and reduce pinholes in the perovskite films, as confirmed by field-emission scanning electron microscopy. The X-ray diffraction profiles of CH3NH3PbI3-xClx clearly showed peaks at 14° and 28° for the samples with additives, indicative of crystallinity. The best PSC performance with a power conversion efficiency of 9.13%, was achieved using 0.1 M NH4I by annealing for 5 min, whereas the power conversion efficiency of the perovskite solar cells without additives was 5.40%.