Lead Halide Perovskite Research Articles

Crown Ethers with Different Cavity Diameters Inhibit Ion Migration and Passivate Defects toward Efficient and Stable Lead Halide Perovskite Solar Cells.

Organic-inorganic hybrid metal halide perovskite solar cells have been considered as one of the most promising next-generation photovoltaic technologies. Nevertheless, perovskite defects and Li+ ionic migration will seriously affect the power conversion efficiency and stability of the formal device. Herein, we designed two crown ether derivatives (PC12 and PC15) with different cavity diameters, which selectively bind to different metal cations. It is found that PC15 in perovskite precursor solution can actively regulate the nucleation and crystallization processes and passivate the uncoordinated Pb2+ ions, while PC12 at the interface between the perovskite layer and hole-transporting layer can effectively inhibit the migration of Li+ ions and reduce nonradiative recombination losses. Therefore, PC12 and PC15 can act as "lubricant" and defect passivators, as well as inhibitors of ion migration, when they are synergistically applied at the surface and bulk of perovskite layer. Consequently, the optimized device achieved a champion efficiency of 24.8% with significantly improved humidity, thermal, and light stability.

Understanding the Mechanisms of Methylammonium-Induced Thermal Instability in Mixed-FAMA Perovskites.

Despite a recent shift toward methylammonium (MA)-free lead-halide perovskites for perovskite solar cells, high-efficiency formamidinium lead iodide (FAPbI3) devices still often require methylammonium chloride (MACl) as an additive, which evaporates away during the annealing process. In this article, it is shown that the residual MA+, however, triggers thermal instability. To investigate the possibility of an optimal concentration of MA+ that may improve thermal stability, the intrinsic thermal stability of pure FA, FA-rich, MA-rich, and pure MA perovskite films (FA1-xMAxPbI3, FAMA) is studied. The results show that the thermal stability of FAMA perovskites decreases with more MA+, under degradation conditions that isolate the intrinsic thermal stability of the material (i.e., without moisture and oxygen effects). X-ray diffraction (XRD), proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS), photoluminescence (PL) and UV-visible spectroscopy, and depth-profiling X-ray Photoelectron Spectroscopy (XPS) are employed to show that the observed trend is mainly due to the decomposition of the MA+ cation, as opposed to other effects such as the precursor solvent and film morphologies. It is also found that the surfaces of these FAMA films are MA+ rich, although this phenomenon does not appear to affect thermal stability. Finally, it is demonstrated that this trend is unaffected by the presence of Spiro-OMeTAD atop the film, and thus solar cell devices should preserve this trend.

Surface Structure of Lecithin-Capped Cesium Lead Halide Perovskite Nanocrystals Using Solid-State and Dynamic Nuclear Polarization NMR Spectroscopy.

Inorganic colloidal cesium lead halide perovskite nanocrystals (NCs) encapsulated by surface capping ligands exhibit tremendous potential in optoelectronic applications, with their surface structure playing a pivotal role in enhancing their photophysical properties. Soy lecithin, a tightly binding zwitterionic surface-capping ligand, has recently facilitated the high-yield synthesis of stable ultraconcentrated and ultradilute colloids of CsPbX3 NCs, unlocking a myriad of potential device applications. However, the atomic-level understanding of the ligand-terminated surface structure remains uncertain. Herein, we use a versatile solid-state nuclear magnetic resonance (NMR) spectroscopic approach, in combination with dynamic nuclear polarization (DNP) and atomistic molecular dynamics (MD) simulations, to explore the effect of lecithin on the core-to-surface structures of CsPbX3 (X = Cl or Br) perovskites, sized from micron to nanoscale. Surface-selective (cross-polarization, CP) solid-state and DNP NMR (133Cs and 207Pb) methods were used to differentiate the unique surface and core chemical environments, while the head-groups {trimethylammonium [-N(CH3)3+] and phosphate (-PO4-)} of lecithin were assigned via 1H, 13C, and 31P NMR spectroscopy. A direct approach to determining the surface structure by capitalizing on the unique heteronuclear dipolar couplings between the lecithin ligand (1H and 31P) and the surface of the CsPbCl3 NCs (133Cs and 207Pb) is demonstrated. The 1H-133Cs heteronuclear correlation (HETCOR) DNP NMR indicates an abundance of Cs on the NC surface and an intimate proximity of the -N(CH3)3+ groups to the surface and subsurface 133Cs atoms, supported by 1H{133Cs} rotational-echo double-resonance (REDOR) NMR spectroscopy. Moreover, the 1H-31P{207Pb} CP REDOR dephasing curve provides average internuclear distance information that allows assessment of -PO4- groups binding to the subsurface Pb atoms. Atomistic MD simulations of ligand-capped CsPbCl3 surfaces aid in the interpretation of this information and suggest that ligand -N(CH3)3+ and -PO4- head-groups substitute Cs+ and Cl- ions, respectively, at the CsCl-terminated surface of the NCs. These detailed atomistic insights into surface structures can further guide the engineering of various relevant surface-capping zwitterionic ligands for diverse metal halide perovskite NCs.

Synthesis and characterization of novel double perovskite K2AgBiBr6

Over the past few years, Lead-free halide double perovskites have attracted a tremendous attention such that it is demonstrated by the power conversion efficiency's sharp increase of over 25 %. It has also stimulated a widespread application of halide metal perovskites in other fields, such as light-emitting diodes, field-effect transistors, detectors, and lasers. Double perovskites have been put forth as an alternative to hybrid lead halide perovskites in the last decade because of their efficiency in doing away with the existing toxicity and instability. It is probably the first attempt, to date, that lead-free halide double perovskite K2AgBiBr6 has been made with a cheap, easy-to-use solution-state reaction method. To determine their structure, single crystal X-ray diffraction and PXRD analysis have been employed. The synthesized K2AgBiBr6 adopts the cubic structure with Fm‾3m symmetry and lattice parameters of a = 6.606 (9) Å at room temperature, according to the diffraction result. Energy dispersive X-ray spectroscopy (EDX), elemental mapping, and scanning electron microscopy (SEM) have all been employed to analyze the morphology and elemental composition. Elements including K, Bi, Ag, and Br have been confirmed to be present in the synthesized sample by the EDX technique. For K2AgBiBr6, the 2.859 eV (indirect) and 3.076 eV (direct) bandgaps have been estimated by employing the UV–Vis absorption spectra. Furthermore, the K2AgBiBr6 double perovskite nanocrystal's thermogravimetric analysis/differential thermal and differential scanning analysis (TG/DTA and DSC) curves at 20–800 °C have been measured. An analysis has been conducted on the mechanism of thermal decomposition of synthesized double perovskite. This work demonstrates great promise for future band gap engineering-based photovoltaic and other optoelectronic applications, and it offers a novel path to obtaining premium K2AgBiBr6 double perovskite.

Enhanced Stability and Performance Lead Halide Perovskite Solar Cells via Hole Transport Materials Additive Strategies

AbstractPast few years has witnessed a rapid surge in the design and fabrication of lead halide perovskite solar cells (LH‐PSCs). Methyl ammonium lead iodide (CH3NH3PbI3) is one of the widely used visible light absorbing material towards the fabrication of LH‐PSCs. The CH3NH3PbI3 has a band gap of around 1.55 eV which makes it a suitable visible light sensitizer for the development of high performance next generation LH‐PSCs. In this work, CH3NH3PbI3 has been explored as visible light absorbing layer with mesoscopic device architecture of (FTO/TiO2/CH3NH3PbI3/spiro‐OMeTAD+MoS2/Au) LH‐PSCs. MoS2 has been utilized as hole transport material additive which not only acted as additive but also enhanced the performance of the LH‐PSCs with long term stability. The FTO/TiO2/CH3NH3PbI3/spiro‐OMeTAD+MoS2/Au showed the interesting efficiency of 14.2 % which is higher than that of the FTO/TiO2/CH3NH3PbI3/spiro‐OMeTAD/Au device (11.9 %). This work offers the fabrication of stable and improved LH‐PSCs with device architecture of FTO/TiO2/CH3NH3PbI3/spiro‐OMeTAD+MoS2/Au.

Fusing Science with Industry: Perovskite Photovoltaics Moving Rapidly into Industrialization.

The organic-inorganic lead halide per materials have emerged as highly promising contenders in the field of photovoltaic technology, offering exceptional efficiency and cost-effectiveness. The commercialization of perovskite photovoltaics hinges on successfully transitioning from lab-scale perovskite solar cells to large-scale perovskite solar modules (PSMs). However, the efficiency of PSMs significantly diminishes with increasing device area, impeding commercial viability. Central to achieving high-efficiency PSMs is fabricating uniform functional films and optimizing interfaces to minimize energy loss. This review sheds light on the path toward large-scale PSMs, emphasizing the pivotal role of integrating cutting-edge scientific research with industrial technology. By exploring scalable deposition techniques and optimization strategies, the advancements and challenges in fabricating large-area perovskite films are revealed. Subsequently, the architecture and contact materials of PSMs are delved while addressing pertinent interface issues. Crucially, efficiency loss during scale-up and stability risks encountered by PSMs is analyzed. Furthermore, the advancements in industrial efforts toward perovskite commercialization are highlighted, emphasizing the perspective of PSMs in revolutionizing renewable energy. By highlighting the scientific and technical challenges in developing PSMs, the importance of combining science and industry to drive their industrialization and pave the way for future advancements is stressed.

Enhanced photocatalytic CO2 conversion into reusable fuels with efficient solid-state proton donors

Lead halide perovskites driven photocatalytic CO2 reduction reaction (CO2RR) is restricted by H2O proton source due to the poor water-resistance of perovskites and difficult dissociation of H2O molecules. In this paper, a novel solid-state proton donor of amino acid modified melamine foam (Ami-MF) is developed, which could improve CO2RR of CsPbBr3/Bi2WO6 S-scheme heterojunction. On the one hand, amino acid molecules possess abundant –COOH and –NH2 groups, which are broken easily by catalyst oxidation compared with H2O, supplying sufficient protons for CO2RR. Product yield of Glu-MF/CsPbBr3/Bi2WO6 reaches 112.81 μmol/g/h, which is 3.8 times higher than that (29.83 μmol/g/h) of H2O-MF/CsPbBr3/Bi2WO6. Moreover, glutamic acid (Glu), cysteine (Cys), arginine (Arg) as typical acidic, neutral and basic amino acids are selected to explore proton supply from different amino acids. Glu-MF/CsPbBr3/Bi2WO6 exhibits the best CO2RR than other two Ami-MF, ascribing to the dicarboxylic structure of Glu. On the other hand, MF is an integral part in solid-state proton donor. Product yield of Glu-MF/CsPbBr3/Bi2WO6 is about 46.2 times higher than that (2.44 μmol/g/h) of powdery Glu/CsPbBr3/Bi2WO6, which ascribes to the efficient gas–solid CO2RR system induced by the three-dimensionality and porosity of MF. This study develops an efficient solid proton donor to enhance perovskites driven CO2RR.

Estimating the Optically Pumped Threshold Fluence of Thin‐Film Gain Media Using Arbitrary Excitation Beams

Optically pumped threshold fluences are a widely reported metric to benchmark the performance of thin‐film gain media and lasers. Estimating the threshold fluence for nonhomogeneous beams, such as a circular Gaussian excitation, is not trivial since the average fluence depends on the estimated spot diameter. Using an exemplary lead halide perovskite film, the inversion volume at different pump energies is mapped. It is shown that the peak fluence of an arbitrary spatial beam profile is more relevant at the threshold, as it provides an upper bound to the threshold fluence. Also, simple conversion factors to estimate the peak fluence using Gaussian excitation beams are provided and the methodology to arbitrary profiles is extrapolated. Furthermore, it is advocated for using flat‐top or uniform stripe excitations to unambiguously extract the threshold fluence, since these excitations display minor discrepancies between the average and peak fluence, and keep the inversion volume relatively constant during the measurement.

Exploring the Effects of Structural and Surface Modifications of Lead Halide Perovskite Nanocrystals on Photocatalytic CO2 Reduction: A Holistic Perspective

Exploring the Effects of Structural and Surface Modifications of Lead Halide Perovskite Nanocrystals on Photocatalytic CO₂ Reduction: A Holistic Perspective

Stabilization of Organic Cations in Lead Halide Perovskite Solar Cells Using Phosphine Oxides Derivatives.

Preventing ion migration in perovskite photovoltaics is key to achieving stable and efficient devices. The activation energy for ion migration is affected by the chemical environment surrounding the ions. Thus, the migration of organic cations in lead halide perovskites can be mitigated by engineering their local interactions, for example through hydrogen bonding. Ion migration also leads to ionic losses via interfacial reactions. Undesirable reactivities of the organic cations can be eliminated by introducing protecting groups. In this work, we report bis(2-oxo-3-oxazolidinyl) phosphinic chloride (BOP-Cl) as a perovskite ink additive with the following benefits: (1) The phosphoryl and two oxo groups form six-membered intermolecular hydrogen-bonded rings with the formamidinium cation (FA), mitigating ion migrations. (2) The hydrogen bonding reduces the electrophilicity of the ammonium protons by donating electron density, therefore reducing its reactivity with the surface oxygen on the metal oxide. Furthermore, the molecule can react to form a protecting group on the nucleophilic oxygen at the tin oxide transport layer surface through the elimination of chlorine. As a result, we achieve perovskite solar cells with an efficiency of 25.0% and improved MPP stability T93 = 1200 h at 40-45 °C compared to a control device (T86 = 550 h). In addition, we show a negative correlation between the strength of hydrogen bonding of different phosphine oxide derivatives to the organic cations and the degree of metastable behavior (e.g., initial burn-in) of the device.

Slowing hot carriers cooling dynamics via perovskite morphology manipulating enable high-performance perovskite solar cells

Slowing hot carriers (HCs) cooling of lead halide perovskites exhibits great promise for achieving highly efficient perovskite solar cells (PSCs). However, the effect of the quality of perovskite on PSCs performance has not been well studied. Herein, we fabricated high-quality perovskite films by employing an organic small molecule, tris(pentafluorophenyl)borane (TFB) as an additive material. It was found that the perovskite films with TFB become smoother and pinhole-free morphology with increased grain size and reduced trap-state density. More importantly, ultrafast transient absorption spectroscopy results reveal that the high-quality TFB-doped perovskite films can significantly slow down HCs cooling process compared with pristine perovskite film, which is beneficial for prolonging the lifetime of carriers and reducing the charge carrier recombination in the device. Accordingly, the power conversion efficiency (PCE) of CsFAMA-based PSCs doping with TFB is enhanced to 22.56% from the control device (20.22%). Compared with 21.79% efficiency for the control device, a high PCE of 24.09% is obtained in FA-based PSCs treated with TFB. Besides, the unencapsulated TFB-doped device retains 91% of its initial value after storing for 1900 h under ambient conditions (∼45% humidity). These findings provide some insights for understanding HCs’ dynamics for constructing highly efficient PSCs.

Long-Range Self-Hybridized Exciton-Polaritons in Two-Dimensional Ruddlesden-Popper Perovskites.

Lead halide perovskites have emerged as platforms for exciton-polaritonic studies at room temperature, thanks to their excellent photoluminescence efficiency and synthetic versatility. In this work, we find proof of strong exciton-photon coupling in cavities formed by the layered crystals themselves, a phenomenon known as the self-hybridization effect. We use multilayers of high-quality Ruddlesden-Popper perovskites in their 2D crystalline form, benefiting from their quantum-well excitonic resonances and the strong Fabry-Pérot cavity modes resulting from the total internal reflection at their smooth surfaces. Optical spectroscopy reveals bending of the cavity modes typical for exciton-polariton formation, and absorption and photoluminescence spectroscopy shows splitting of the excitonic resonance and thickness-dependent peak positions. Strikingly, local optical excitation with energy below the excitonic resonance of the flakes in photoluminescence measurements unveils the coupling of light to in-plane polaritonic modes with directed propagation. These exciton-polaritons exhibit high coupling efficiencies and extremely low loss propagation mechanisms, which are confirmed by finite difference time domain simulations. Thus, we prove that mesoscopic 2D Ruddlesden-Popper perovskite flakes represent an effective but simple system to study the rich physics of exciton-polaritons at room temperature.

Enhancing the performance of lead halide perovskite solar cells and reducing its toxicity using nanostructures

Enhancing the performance of lead halide perovskite solar cells and reducing its toxicity using nanostructures

Dynamics of glassy state in MAPbBr3-xClx mixed lead halide perovskites

Mixed lead halide perovskites have shown remarkable performance in photovoltaic and optoelectronic applications. Pure hybrid halide perovskites undergo clear phase transitions, however, the phase transitions in mixed perovskites are less studied. We present a contrasting behavior of the phase transition dynamics of MAPbBr3-xClx (MA = CH3NH3+) mixed halide perovskites compared to the pure MAPbX3 (X = Cl, Br) counterparts, which typically exhibit order-disorder phase transitions through a series of distinct structural phases. We have employed several spectroscopic techniques including temperature-dependent PXRD, Raman, dielectric and Brillouin spectroscopy. The results demonstrate that the mixed halide perovskite MAPbBr1.5Cl1.5 does not undergo any structural phase transition typically observed in pure halide perovskites. We observed signatures of glassy behavior in mixed compositions of this system. In addition, we also explored the effects of replacing A-site cation on the phase transition behaviors. The results contribute to the understanding of phase transition mechanisms in perovskites and have implications for their stability and optoelectronic properties.

Studying of the structural and optical properties of lead halide perovskite and useing in detecting ammonia gas

Studying of the structural and optical properties of lead halide perovskite and useing in detecting ammonia gas

Coupled Kite-to-Square Distortion Transition and Physical Properties in 2D Lead Halide Perovskite.

2D lead halide perovskites showcase diverse electrical and optoelectrical properties due to their adaptable structural distortion, which dictates the symmetry characteristics of the material. To accommodate the geometric shape of the cation, the inorganic layer of the 2D perovskite often undergoes specific distortions such as lead-halide bond length elongation/compression and lead atom displacement. The resultant distortion manifests as a quadrilateral shape formed by Pb atoms from four adjacent four octahedrons. The degree of distortion increases as the quadrilateral deviates further from a square shape and vice versa. This quadrilateral shape not only visually represents the magnitude of distortion but also confirms its direction. During the transition from kite to square distortion under external stimuli, the positions of the Pb atoms vividly illustrate the symmetry-breaking process, corresponding to a shift from high to low symmetry states. The electrical and optoelectronic properties, including ferroelectricity, pyroelectricity, piezoelectricity, nonlinear optical properties, and characteristics related to bulky photovoltaic effects, some of them exhibit direction dependence nature. This perspective employed a visible structural distortion approach to elucidate symmetry breaking and coupling distortion transitions with eight optoelectronic physical properties in 2D layered perovskite. We review recent research advancements and outline current challenges that help us to understand the structure-property relationship of 2D perovskite.

Near‐Unity Green Luminescent and Stable Lead‐Free Cs3Cu2Cl5 Nanocrystals Assisted by MnC2O4 Treatment

AbstractThe toxicity and chemical instability shortcomings of lead halide perovskites are major concerns that continue to motivate the search for next generation alternatives. Copper halides are known to be lead‐free, earth‐abundant, low‐cost, and environmentally friendly, and affordable in optoelectronic performance due to their bright luminescence, tunable emission wavelength, and excellent stability. However, the controlled synthesis of low‐dimensional copper halide nanocrystals (NCs) with near‐unity photoluminescence quantum yield (PLQY) and high stability remains a great challenge. In this work, we report a reasonable optimization approach for the preparation of Cs3Cu2Cl5 NCs by hot‐injection colloidal synthesis technology. Specifically, the Cs3Cu2Cl5 NCs synthesized with MnC2O4 as the defect repair agent exhibited negligible self‐absorption, bright green luminosity with PL emission at about 535 nm and PLQY can be increased from 68.7 % to 100 %. The Cs3Cu2Cl5 NCs shows excellent stability and outstanding optical properties, and is expected to be used as highly efficient green light emitter in high‐efficiency X‐ray scintillator.

Chiral 3D Perovskite Formation Induced by Chiral Templates.

Chiral 3D perovskites pose challenges compared to lower-dimensional variants due to limited chiral organic cation options. Here, we present a universal and controlled method for synthesizing chiral 3D lead halide perovskites using organic amines or alcohols as chiral templates. Introducing these templates to PbCl2 in N,N-dimethylformamide (DMF) under acidic conditions induces the crystallization of R/S [DMA]PbCl3 (DMA = dimethylamine). The resulting structure aligns with the templates used, stemming from the helical Pb2Cl95- chain as verified by single-crystal X-ray diffraction. Furthermore, the chiral perovskite exhibits absorption and circular dichroism (CD) signals in the high-energy band, enabling the circularly polarized light (CPL) detection in the UV spectrum. A CPL detector constructed by this chiral perovskite demonstrates excellent performance, boasting an anisotropy factor for photocurrent (gIph) of 0.296. Our work not only introduces a novel and controllable method for crafting chiral perovskites but also opens new avenues for circularly polarized light detection.

PVDF nanostructures characterizations and techniques for enhanced piezoelectric response: A review

Polymeric polyvinylidene fluoride (PVDF) nanofibers have drawn more attention due to their superior mechanical strength, piezoelectric qualities, and thermal stability. PVDF is regarded as a popular fluoropolymer. It is easily processed and possesses chemical resistance to a variety of substances, including various acids, bases, organic solvents, oil, and fat. Among the most extensively studied polymers with piezoelectric characteristics is PVDF. It was noted in the literature that increasing the β-phase in PVDF crystals and fibers increased the material's electromechanical properties. The β-phase concentration of PVDF has been increased by several studies over the last few decades, utilizing a variety of processing methods and additives. Electrospinning is one of these processing techniques. The development of electrospinning technology enabled precise tweaking of the β-phase. Pure polymer materials only have a restricted number of applications because of their small β-phase percentage. To address this issue, using nanofibers (NFs) to create composite materials is an extremely attractive design strategy for piezoelectric materials. This work reviews the impact of several nanoadditives, such as metal oxides, carbon-based materials, organic and inorganic lead halide perovskites, and some other fillers, on the piezoelectric behavior of PVDF and its copolymer structure. This paper makes an effort to provide a general overview of the electrospinning procedure for PVDF, a piezoelectric polymer, as well as the approach used to characterize its β-phase and composite materials made with NFs. With an emphasis on creating a suitable crystalline structure in the PVDF material, this study seeks to give commentary from a materials chemistry standpoint.

Lead-free Ce-doped perovskite scintillators with high figure of merit

Lead halide perovskite scintillators have recently received extensive research attention owing to their short fluorescence lifetimes, low detection limits, and ease of fabrication compared to traditional scintillators. The nontoxic cerium-doped lead-free perovskites with intrinsically efficient and short lifetime d–f transitions are a prospective replacement for the toxic Pb2+. Here, we demonstrated Ce-doped cesium lanthanide chloride perovskites (Cs3LnCl6, Ln = Gd, Y, Lu) synthesized through a facile solution method for the first time. These perovskites exhibit blue-violet emission, which arises from Ce 5d → 4f transitions. Among three types of Cs3LnCl6 perovskites, Ce:Cs3LuCl6 exhibited high photoluminescence quantum yield (PLQY) of 82% and a short excited-state lifetime of approximately 34 ns. When utilized as X-ray scintillators, Ce:Cs3LuCl6 crystals display a high light yield of 8120 photons per MeV and a low detection limit of 36.8 nGy air s−1. Importantly, the figure of merit (FoM), representing the ratio of light yield to decay time, reaches 239, which is the highest reported value for lead-free perovskite scintillators up to now. Additionally, the fabrication of perovskite/PMMA films was undertaken for practical demonstrations in X-ray imaging, resulting in the attainment of a resolution of up to 8.38 lp/mm. We anticipate that this work will inspire the utilization of Ce-doped Cs3LnCl6 perovskites in ultrafast scintillation applications such as high-energy physics, nuclear reaction monitoring, and dynamic X-ray imaging.