Bithiophene Imide-Based Self-Assembled Monolayers (SAMs) on NiOx for High-Performance Tin Perovskite Solar Cells Fabricated Using a Two-Step Approach.

Three new bithiophene imide (BTI)-based organic small molecules, (), (), and (), with varied alkyl side chains, were developed and employed as self-assembled monolayers (SAMs) applied to NiOx films in tin perovskite solar cells (TPSCs). The NiOx layer has the effect of modifying the hydrophilicity and the surface roughness of ITO for SAM to uniformly deposit on it. The side chains of the SAM molecules play a vital role in the formation of a high-quality perovskite layer in TPSCs.

Solvent-Free Ball Milling Synthesis of Water-Stable Tin-Based Pseudohalide Perovskites for Photocatalytic CO Reduction.

A pseudohalide (SCN) tin-based perovskite material using a solvent-free ball milling method is developed. The synthesized perovskite exhibits long-term water stability and demonstrated significant photocatalytic activity in reducing CO to CO under light irradiation. The structural transition from nanoparticles to planar perovskites is achieved by varying the ratios of dimethylammonium (DMA) and formamidinium (FA) cations, which is confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses.

Photocatalytic CO Reduction Using Zinc Indium Sulfide Aggregated Nanostructures Fabricated under Four Anionic Conditions.

Zinc indihuhium sulfide (ZIS), among various semiconductor materials, shows considerable potential due to its simplicity, low cost, and environmental compatibility. However, the influence of precursor anions on ZIS properties remains unclear. In this study, we synthesized ZIS via a hydrothermal method using four different anionic precursors (ZnCl/InCl, Zn(NO)/In(NO), Zn(CHCO)/In(CHCO), and Zn(CHCO)/In(SO)), resulting in distinct morphologies and crystal structures.

Co-Cation Engineering via Mixing of Acetamidinium and Rubidium in FASnI for Tin Perovskite Solar Cells to Attain 14.5% Efficiency.

Tin perovskite solar cells (TPSCs) were developed by adding the co-cations acetamidinium (AC) and rubidium (Rb) in varied proportions based on the FASnI structure (E1). We found that adding 10% AC and 3% Rb can optimize the device (E1AC10Rb3) to attain an efficiency of power conversion of 14.5% with great shelf- and light-soaking stability.

Functionalized Thienopyrazines on NiOx Film as Self-Assembled Monolayer for Efficient Tin-Perovskite Solar Cells Using a Two-Step Method.

Three functionalized thienopyrazines (TPs), TP-MN (1), TP-CA (2), and TPT-MN (3) were designed and synthesized as self-assembled monolayers (SAMs) deposited on the NiOx film for tin-perovskite solar cells (TPSCs). Thermal, optical, electrochemical, morphological, crystallinity, hole mobility, and charge recombination properties, as well as DFT-derived energy levels with electrostatic surface potential mapping of these SAMs, have been thoroughly investigated and discussed. The structure of the TP-MN (1) single crystal was successfully grown and analyzed to support the uniform SAM produced on the ITO/NiOx substrate.

Dual-plasmonic Au@CuS yolk@shell nanocrystals for photocatalytic hydrogen production across visible to near infrared spectral region.

Near infrared energy remains untapped toward the maneuvering of entire solar spectrum harvesting for fulfilling the nuts and bolts of solar hydrogen production. We report the use of Au@CuS yolk@shell nanocrystals as dual-plasmonic photocatalysts to achieve remarkable hydrogen production under visible and near infrared illumination. Ultrafast spectroscopic data reveal the prevalence of long-lived charge separation states for Au@CuS under both visible and near infrared excitation.

Expression of concern: Versatile plasmonic-effects at the interface of inverted perovskite solar cells.

Expression of concern for 'Versatile plasmonic-effects at the interface of inverted perovskite solar cells' by Ahmed Esmail Shalan, , , 2017, , 1229-1236, https://doi.org/10.1039/C6NR06741G.

Highly Efficient HTM-Free Tin Perovskite Solar Cells with Outstanding Stability Exceeding 10000 h.

The bottleneck in the rapid development of tin-based perovskite solar cells (TPSCs) is the inherent chemical instability. Although this is being addressed continuously, the device performance has not improved further due to the use of PEDOT:PSS as the hole-transport material (HTM), which has poor long-term stability. Herein we have applied commercial ITO nanoparticles over ITO glass substrates and altered the surface chemistry of the ITO electrode via a simple two-step thermal annealing, followed by a UV-ozone treatment.

Effect of Acidic Strength of Surface Ligands on the Carrier Relaxation Dynamics of Hybrid Perovskite Nanocrystals.

Perovskite nanocrystals (PeNCs) are known for their use in numerous optoelectronic applications. Surface ligands are critical for passivating surface defects to enhance the charge transport and photoluminescence quantum yields of the PeNCs. Herein, we investigated the dual functional abilities of bulky cyclic organic ammonium cations as surface-passivating agents and charge scavengers to overcome the lability and insulating nature of conventional long-chain type oleyl amine and oleic acid ligands.

Dopant-Free Pyrrolopyrrole-Based (PPr) Polymeric Hole-Transporting Materials for Efficient Tin-Based Perovskite Solar Cells with Stability Over 6000 h.

A new set of pyrrolopyrrole-based (PPr) polymers incorporated with thioalkylated/alkylated bithiophene (SBT/BT) is synthesized and explored as hole-transporting materials (HTMs) for Sn-based perovskite solar cells (TPSCs). Three bithiophenyl spacers bearing the thioalkylated hexyl (SBT-6), thioalkylated tetradecyl (SBT-14), and tetradecyl (BT-14) chains are utilized to examine the effect of the alkyl chain lengths. Among them, the TPSCs are fabricated using PPr-SBT-14 as HTMs through a two-step approach by attaining a power conversion efficiency (PCE) of 7.

Energy and Charge Transfer Dynamics in Red-Emitting Hybrid Organo-Inorganic Mixed Halide Perovskite Nanocrystals.

We report time-resolved spectral properties of highly stable and efficient red-emitting hybrid perovskite nanocrystals with the composition FAMAPbBrI (FAMA PeNC) synthesized by using the hot-addition method. The PL spectrum of the FAMA PeNC shows a broad asymmetric band covering 580 to 760 nm with a peak at 690 nm which can be deconvoluted into two bands corresponding to the MA and FA domains. The interactions between the MA and FA domains are shown to affect the relaxation dynamics of the PeNCs from the subpicosecond to tens of nanoseconds scale.

Retarded Charge Recombination to Enhance Photocatalytic Performance for Water-Free CO Reduction Using Perovskite Nanocrystals as Photocatalysts.

Femtosecond transient absorption spectral (TAS) investigations were performed to understand the carrier relaxation mechanism for perovskite nanocrystals CsFAPbBr (CF, = 0.45) and CsPbBr (CS), which served as efficient photocatalysts for splitting of CO into CO and O in the absence of water. Upon light irradiation for 12 h, formation of deep trap states was found for both CS and CF samples with spectral characteristics of the TAS photobleach (PB) band showing a long spectral tail extending to the long wavelength region.

Interface-Enhanced Charge Recombination in the Heterojunction between Perovskite Nanocrystals and BiOI Nanosheets Serves as an S-Scheme Photocatalyst for CO Reduction.

We designed an S-heterojunction system with a perovskite nanocrystal, CsFAPbBr (CF), coupled with a bismuth oxyiodide (BiOI) nanosheet to form a perovskite heterojunction (PHJ) photocatalyst. On the basis of femtosecond transient absorption measurements, the pristine CF sample has two charge recombination periods, 100 and 900 ps, corresponding to surface and bulk trap-state relaxations, respectively. When CF was in contact with BiOI to form an S-heterojunction, rapid interfacial charge recombination occurred to show two decay components with time coefficients 1 and 35 ps, responsible for the electron-hole recombination in the surface and bulk states, respectively.

Electrodeposition of CoNiVO Ternary Nanopetals on Bare and rGO-Coated Nickel Foam for High-Performance Supercapacitor Application.

We report a simple strategy to grow a novel cobalt nickel vanadium oxide (CoNiVO) nanocomposite on bare and reduced-graphene-oxide (rGO)-coated nickel foam (Ni foam) substrates. In this way, the synthesized graphene oxide is coated on Ni foam, and reduced electrochemically with a negative voltage to prepare a more conductive rGO-coated Ni foam substrate. The fabricated electrodes were characterized with a field-emission scanning electron microscope (FESEM), energy-dispersive X-ray spectra (EDX), X-ray photoelectron spectra (XPS), and Fourier-transform infrared (FTIR) spectra.

Femtosecond Exciton and Carrier Relaxation Dynamics of Two-Dimensional (2D) and Quasi-2D Tin Perovskites.

The dynamics of exciton and free-carrier relaxation of low-dimensional tin iodide perovskites, BAFASnI, where = 1 (N1), 2 (N2), 5 (N5), and 10 (N10), were investigated with femtosecond transient absorption spectra (TAS). The absorption and photoluminescence spectra of N1 and N2 show exciton characteristics due to quantum confinement, whereas N5 and N10 display a free-carrier nature, the same as for bulk three-dimensional (3D) films. The TAS profiles were fitted according to a global kinetic model with three time coefficients representing the interactions of biexcitons, trions, and excitons for N1 and N2 and hot carriers, cold carriers, and shallow trap carriers for N5 and N10.

Slow Passivation and Inverted Hysteresis for Hybrid Tin Perovskite Solar Cells Attaining 13.5% via Sequential Deposition.

Herein, we report a sequential deposition procedure to passivate the surface of a hybrid mixed cationic tin perovskite (E1G20) with phenylhydrazinium thiocyanate (PHSCN) dissolved in trifluoroethanol solvent. The photoluminescence lifetime of the PHSCN film was enhanced by a factor of 6, while the charge-extraction rate from perovskite to C layer was enhanced by a factor of 2.5, in comparison to those of the E1G20 film.

Mixing of Azetidinium in Formamidinium Tin Triiodide Perovskite Solar Cells for Enhanced Photovoltaic Performance and High Stability in Air.

Overcoming the issue of the stability of tin-based perovskites is a major challenge for the commercial development of lead-free perovskite solar cells. To attack this problem, a new organic cation, azetidinium (AZ), is incorporated into the crystal structure of formamidinium tin triiodide (FASnI ) to form the mixed-cation perovskite AZ FA SnI . As AZ has a similar size to FA but a larger dipole moment, hybrid AZ FA SnI films exhibit variation in optical and electronic properties on increasing the proportion of AZ.

Environmentally Compatible Lead-Free Perovskite Solar Cells and Their Potential as Light Harvesters in Energy Storage Systems.

Next-generation renewable energy sources and perovskite solar cells have revolutionised photovoltaics research and the photovoltaic industry. However, the presence of toxic lead in perovskite solar cells hampers their commercialisation. Lead-free tin-based perovskite solar cells are a potential alternative solution to this problem; however, numerous technological issues must be addressed before the efficiency and stability of tin-based perovskite solar cells can match those of lead-based perovskite solar cells.

A Direct Mapping Approach to Understand Carrier Relaxation Dynamics in Varied Regions of a Polycrystalline Perovskite Film.

We developed a direct mapping approach to overlay the image of a polycrystalline perovskite film obtained from the transient absorption microscope (TAM) with that from the scanning electron microscope (SEM). By mapping these imaging data pixel by pixel, we are able to observe the relaxation dynamics of the photo-generated charge carriers on varied regions of the film. The carrier relaxation dynamics contain a dominated single-exponential decay component owing to the recombination of charge carriers.

Femtosecond Transient Absorption Spectra and Dynamics of Carrier Relaxation of Tin Perovskites in the Absence and Presence of Additives.

The effects of additives SnF (10%) and EDAI (1%) on the dynamics of carrier relaxation of formamidinium tin triiodide (FASnI) perovskite were studied using femtosecond transient absorption spectra (TAS) with excitation at 600 and 870 nm. The TAS were analyzed according to a parallel sequential kinetic model with a global fit through singular-value decomposition. For excitation at 600 nm, two relaxation paths were found: one involved hot and cold carriers in the bulk state undergoing shallow bulk-defect-mediated charge recombination; the other involved trap carriers in the surface state undergoing deep surface-defect-mediated charge recombination.

Inter- and Intragrain Inhomogeneity in 2D Perovskite Thin Films Revealed by Relative Grain Orientation Imaging Using Low-Frequency Polarized Raman Microspectroscopy.

Two-dimensional (2D) organic-inorganic hybrid lead halide perovskites make up an emerging class of semiconductor materials for optoelectronic applications such as solar cells. The grain structure of polycrystalline 2D perovskites is one of the key factors that dictate their functionality in the devices, but currently available methods for in situ, chemically specific characterization of 2D perovskite grains are scarce. Here we show that ultra-low-frequency polarized Raman microspectroscopy is a facile yet powerful tool for visualizing relative grain orientations within 2D perovskite thin films.

Development of Hybrid Pseudohalide Tin Perovskites for Highly Stable Carbon-Electrode Solar Cells.

Tin-based perovskites degrade rapidly upon interaction with water and oxygen in air because Sn-I bonds are weak. To address this issue, we developed novel tin perovskites, FASnI(SCN) ( = 0, 1, 2, or 3), by employing a pseudohalide, thiocyanate (SCN), as a replacement for halides and as an inhibitor to suppress the Sn/Sn oxidation. The structural and electronic properties of pseudohalide tin perovskites in this series were explored with quantum-chemical calculations by employing the plane-wave density functional theory (DFT) method; the corresponding results are consistent with the experimental results.

Development of Novel Mixed Halide/Superhalide Tin-Based Perovskites for Mesoscopic Carbon-Based Solar Cells.

Tin perovskites suffer from poor stability and a self-doping effect. To solve this problem, we synthesized novel tin perovskites based on superhalide with varied ratios of tetrafluoroborate to iodide and implemented them into solar cells based on a mesoscopic carbon-electrode architecture because film formation was an issue in applying this material for a planar heterojunction device structure. We undertook quantum-chemical calculations based on plane-wave density functional theory (DFT) methods and explored the structural and electronic properties of tin perovskites FASnI(BF) in the series = 0, 1, 2, and 3.

Mechanism of Photocatalytic CO Reduction by Bismuth-Based Perovskite Nanocrystals at the Gas-Solid Interface.

We report here a series of nontoxic and stable bismuth-based perovskite nanocrystals (PeNCs) with applications for photocatalytic reduction of carbon dioxide to methane and carbon monoxide. Three bismuth-based PeNCs of general chemical formulas ABiI, in which cation A = Rb or Cs or CHNH (MA), were synthesized with a novel ultrasonication top-down method. PeNC of CsBiI had the best photocatalytic activity for the reduction of CO at the gas-solid interface with formation yields 14.