Inorganic Lead Halide Perovskite Research Articles

Low‐Power‐Consumption, Reversible 3D Optical Storage Based on Selectively Laser‐Induced Photoluminescence Degradation in CsPbBr3 Quantum Dots Doped Glass

AbstractIn recent years, inorganic lead halide perovskite quantum dots have been used in various optoelectronic fields for their excellent luminescence properties, such as narrow emission bands, ultra‐wide tunable emission wavelength, and high quantum efficiency. In this paper, different from luminescence optimization in most research, luminescence degradation of perovskite quantum dots is addressed by femtosecond laser irradiation and successfully used for three‐dimensional data storage in CsPbBr3 quantum dots doped glass. Photoluminescence (PL) degradation can be finely modulated by adjusting the laser parameters. PL degradation mechanism, investigated by optical spectroscopy and morphology characterization, is attributed to laser‐induced decomposition, recrystallization, and defection of CsPbBr3 quantum dots. Laser‐induced PL degradation and the followed PL recovery by heat treatment are repeated for several cycles, showing good reversibility. Multilayer PL degradation patterns are written into the glass and read out without crosstalk, indicating high‐reliability 3D optical storage characteristics. Amazingly, PL degradation can be induced by just a low‐energy single laser pulse with estimated subpicosecond writing time per bit, demonstrating its potential in high‐speed, low‐power consumption 3D optical storage.

Fluorine-containing organic ammonium salt-doped inverted inorganic perovskite solar cells

Inorganic lead halide perovskites have a reasonable energy bandgap, which makes them ideal for tandem devices. As a result, inorganic lead halide perovskite solar cells (PSCs) could be prospective next-generation solar materials, but the issue of instability under moisture remains unaddressed. Adding 4-fluoro-phenyl-ethylammonium iodide (F-PEAI) spacer cations to the perovskite precursor solution is an elementary addition method to improve the performance of PSCs. We study the impact of F-PEAI on the perovskite crystal phase and the effect of F-PEAI concentration on PSC performance. F-PEAI was used to passivate interfacial flaws and vacancies in inverted inorganic PSCs and improve moisture tolerance, resulting in a mixed 2D/3D heterostructure. A small number of F-PEAI-treated PSCs have changed interfacial characteristics, resulting in better charge extraction and less charge recombination. The power conversion efficiency (PCE) of the F-PEAI treated device is much higher than that of the control group, and the PCE is improved to more than 11%. To attain high efficiency, all-inorganic perovskites can be modified using a straightforward method.

Bi and Sn Doping Improved the Structural, Optical and Photovoltaic Properties of MAPbI3-Based Perovskite Solar Cells

One of the most amazing photovoltaic technologies for the future is the organic–inorganic lead halide perovskite solar cell, which exhibits excellent power conversion efficiency (PCE) and can be produced using a straightforward solution technique. Toxic lead in perovskite can be replaced by non-toxic alkaline earth metal cations because they keep the charge balance in the material and some of them match the Goldschmidt rule’s tolerance factor. Therefore, thin films of MAPbI3, 1% Bi and 0%, 0.5%, 1% and 1.5% Sn co-doped MAPbI3 were deposited on FTO-glass substrates by sol-gel spin-coating technique. XRD confirmed the co-doping of Bi–Sn in MAPbI3. The 1% Bi and 1% Sn co-doped film had a large grain size. The optical properties were calculated by UV-Vis spectroscopy. The 1% Bi and 1% Sn co-doped film had small Eg, which make it a good material for perovskite solar cells. These films were made into perovskite solar cells. The pure MAPbI3 film-based solar cell had a current density (Jsc) of 9.71 MA-cm−2, its open-circuit voltage (Voc) was 1.18 V, its fill factor (FF) was 0.609 and its efficiency (η) was 6.98%. All of these parameters were improved by the co-doping of Bi–Sn. The cell made from a co-doped MAPbI3 film with 1% Bi and 1% Sn had a high efficiency (10.03%).

Photoinduced large polaron transport and dynamics in organic–inorganic hybrid lead halide perovskite with terahertz probes

Organic-inorganic hybrid metal halide perovskites (MHPs) have attracted tremendous attention for optoelectronic applications. The long photocarrier lifetime and moderate carrier mobility have been proposed as results of the large polaron formation in MHPs. However, it is challenging to measure the effective mass and carrier scattering parameters of the photogenerated large polarons in the ultrafast carrier recombination dynamics. Here, we show, in a one-step spectroscopic method, that the optical-pump and terahertz-electromagnetic probe (OPTP) technique allows us to access the nature of interplay of photoexcited unbound charge carriers and optical phonons in polycrystalline CH3NH3PbI3 (MAPbI3) of about 10 μm grain size. Firstly, we demonstrate a direct spectral evidence of the large polarons in polycrystalline MAPbI3. Using the Drude–Smith–Lorentz model along with the Frӧhlich-type electron-phonon (e-ph) coupling, we determine the effective mass and scattering parameters of photogenerated polaronic carriers. We discover that the resulting moderate polaronic carrier mobility is mainly influenced by the enhanced carrier scattering, rather than the polaron mass enhancement. While, the formation of large polarons in MAPbI3 polycrystalline grains results in a long charge carrier lifetime at room temperature. Our results provide crucial information about the photo-physics of MAPbI3 and are indispensable for optoelectronic device development with better performance.

Screening of Excitons by Organic Cations in Quasi-Two-Dimensional Organic-Inorganic Lead-Halide Perovskites.

Interlayer organic cations in quasi-two-dimensional halide perovskites are a versatile tuning vehicle for the optoelectronic properties of these complex systems, but chemical intuition for this design route is yet to be established. Here, we use density functional theory, the GW approximation, and the Bethe-Salpeter equation approach to understand the contribution of the organic cation to the quasiparticle band gap and exciton binding energy of layered perovskites. We show that organic cations in quasi-two-dimensional perovskites contribute significantly to the dielectric screening in these systems, countering quantum confinement effects on the quasiparticle band gap and the exciton binding energy. Using a simple electrostatics model inspired by parallel-plate capacitors, we decouple the organic cation and inorganic layer contributions to the effective dielectric constants and show that dielectric properties of layered perovskites are broadly tunable via the interlayer cation, providing a direct means of tuning photophysical properties for a variety of applications.

Effects of Alkaline Earth Metal Additives on Methylammonium‐Free Lead Halide Perovskite Thin Films and Solar Cells

Organic–inorganic lead halide perovskite solar cells are regarded as one of the most promising technologies for the next generation of photovoltaics due to their high power conversion efficiency (PCE) and simple solution manufacturing. Among the different compositions, the formamidinium lead iodide (FAPbI3) photoactive phase has a bandgap of 1.4 eV, which enables the corresponding higher PCEs according to the Shockley–Queisser limit. However, the photoactive crystal phase of FAPbI3 is not stable at room temperature. The most high‐performing compositions to date have reduced this problem by incorporating the methylammonium (MA) cation into the FAPbI3 composition, although MA has poor stability at high temperatures and in humid environments, which can limit the lifetime of FAxMA1−xPbI3 films. CsxFA1−xPbI3 perovskites are also explored, but despite better stability they still lag in performance. Herein, the additive engineering of MA‐free organic−inorganic lead halide perovskites using divalent cations Sr2+ and Ca2+to enhance the performances of CsxFA1−xPbI3 perovskite compositions is explored. It is revealed that the addition of up to 0.5% of Sr2+ and Ca2+ leads to improvements in morphology and reduction in microstrain. The structural improvements observed correlate with improved solar cell performances at low additive concentrations.

Ethylcellulose‐Encapsulated Inorganic Lead Halide Perovskite Nanoparticles for Printing and Optoelectronic Applications

AbstractInorganic lead halide perovskite nanoparticles (NPs) have attracted attention for next‐generation optoelectronics and anti‐counterfeiting applications. The fully inorganic NPs get degraded in polar solvents resulting in poor stability. These also tend to degrade under exposure to high temperatures resulting in obstacles to application in reliable anti‐counterfeiting and optoelectronics applications. The encapsulation of perovskite NPs with ethyl cellulose (EC) as a polymer matrix to overcome these obstacles is explored using a facile solution blending technique followed by ultra‐sonication and characterization. These NPs demonstrate enhanced photoluminescence (PL) intensity, improved color clarity, and considerable stability. Along with organic binders, they can be used in developing printable ink for making patterns. A logo coated with CsPbBr3 + EC and CsPbBr1.5 I1.5 + EC exposed in normal light and UV light (365 nm) shows a clear image that becomes blue‐green and yellow color. Additionally, the effect of light on the current density–voltage characteristics of the size‐dependent encapsulated NPs shows that photocurrent has dramatically improved over 5.14 times in CsPbBr3 + EC and 1.68 times in CsPbBr1.5 I1.5 + EC compared to that of pristine one. These results demonstrate its potential uses for several applications such as luminescent printing applications, sensors, and optoelectronic applications.

Indigo: A Natural Molecular Passivator for Efficient Perovskite Solar Cells

AbstractOrganic–inorganic hybrid lead halide perovskite solar cells have made unprecedented progress in improving photovoltaic efficiency during the past decade, while still facing critical stability challenges. Herein, the natural organic dye Indigo is explored for the first time to be an efficient molecular passivator that assists in the preparation of high‐quality hybrid perovskite film with reduced defects and enhanced stability. The Indigo molecule with both carbonyl and amino groups can provide bifunctional chemical passivation for defects. In‐depth theoretical and experimental studies show that the Indigo molecules firmly binds to the perovskite surfaces, enhancing the crystallization of perovskite films with improved morphology. Consequently, the Indigo‐passivated perovskite film exhibits increased grain size with better uniformity, reduced grain boundaries, lowered defect density, and retarded ion migration, boosting the device efficiency up to 23.22%, and ≈21% for large‐area device (1 cm2). Furthermore, the Indigo passivation can enhance device stability in terms of both humidity and thermal stress. These results provide not only new insights into the multipassivation role of natural organic dyes but also a simple and low‐cost strategy to prepare high‐quality hybrid perovskite films for optoelectronic applications based on Indigo derivatives.

From film to ring: Quasi-circular inorganic lead halide perovskite grain induced growth of uniform lead silicate glass ring structure

Polycrystalline properties of perovskites can induce the growth of different nanostructures, thanks to their facile fabrication. In this work, the CsPb2Br5 perovskite grains were used as templates to induce the growth of the ring-like structures on a SiO2/Si substrate. Owing to the oxidation of the volatile PbBr2 originated from the decomposition of CsPb2Br5, the grain boundaries of perovskites are prone to reaction with SiO2, which leads to the formation of Pb-silicate glass at high temperatures. The quasi-circular grain structure of CsPb2Br5 defines the final dimension of the Pb-silicate glass ring-like structures. X-ray photoelectron spectroscopy (XPS) measurement results reveal the formation and composition of the Pb-silicate glass ring-like structures converting from the halide perovskite film on the SiO2/Si substrate. Furthermore, these ring-like structures can extend to the field of display and pulsed-laser by combining existing techniques.

Atomic-Level Description of Thermal Fluctuations in Inorganic Lead Halide Perovskites.

A comprehensive microscopic description of thermally induced distortions in lead halide perovskites is crucial for their realistic applications, yet still unclear. Here, we quantify the effects of thermal activation in CsPbBr3 nanocrystals across length scales with atomic-level precision, and we provide a framework for the description of phase transitions therein, beyond the simplistic picture of unit-cell symmetry increase upon heating. The temperature increase significantly enhances the short-range structural distortions of the lead halide framework as a consequence of the phonon anharmonicity, which causes the excess free energy surface to change as a function of temperature. As a result, phase transitions can be rationalized via the soft-mode model, which also describes displacive thermal phase transitions in oxide perovskites. Our findings allow to reconcile temperature-dependent modifications of physical properties, such as changes in the optical band gap, that are incompatible with the perovskite time- and space-average structures.

Submicron Organic–Inorganic Hybrid Radiative Cooling Coatings for Stable, Ultrathin, and Lightweight Solar Cells

Solar cell technology requires materials that are efficient, lightweight, and stable. Organic–inorganic lead halide perovskite- and polymer-based bulk heterojunction solar cells have emerged as highly promising, ultralightweight, flexible, and highly efficient power sources. However, they suffer from limited stability, which is significantly affected by the cell temperature, in addition to other factors like oxidization and moisture in the absence of appropriate encapsulation. Here, by performing a coupled opto-electro-thermal modeling, we report the design of a compatible and novel, ultrathin, submicron, multipurpose organic–inorganic hybrid radiative cooling coating/scheme that, by providing photonic cooling, decreases the cell temperature by up to ∼7.2 K compared to the encapsulated ultrathin solar cell technology, without requiring any external energy input. In addition to the significant temperature reduction, the power conversion efficiency of cells also increases, fulfilling the requirements of high performance at minimal weight, combined with high stability and flexibility, paving the way for next-generation, stable and efficient, ultralightweight solar cells.

Design and optimization of highly efficient perovskite/homojunction SnS tandem solar cells using SCAPS-1D

Double-junction tandem solar cells containing a wide-bandgap top cell and a narrow-bandgap bottom cell have a great potential to outperform current single-junction photovoltaic technologies. However, careful consideration is required in the selection and optimization of both sub-cells to obtain full benefit. In this study, we present numerical simulations of tandem solar cells with tin sulfide (SnS) bottom sub-cells and organic–inorganic lead halide perovskite top sub-cells using SCAPS-1D. The performance of SnS homojunction solar cell optimized by investigation of the p-type and n-type layer thicknesses, doping concentrations, defect densities, and interface defects. Afterward, the perovskite solar cell is optimized in terms of variation in absorber bandgap (1.55–1.75 eV) and thickness (100–800 nm). To properly simulate tandem devices, bottom cells are optically filtered by calculated spectra of perovskite solar cells. Current matching has been done by varying thickness of the perovskite sub-cell with different bandgaps, and the optimized 28.92% efficiency has been revealed for the perovskite/SnS tandem device. This is the first numerical simulation using homojunction SnS as a bottom sub-cell in perovskite tandem solar cells to the best of our knowledge. Results suggest that tin sulfide homojunction solar cells could be a low-cost and environmentally friendly bottom sub-cell for efficient perovskite tandem solar cells.

Unravelling Structure and Formation Mechanisms of Ruddlesden-Popper-Phase-like Nanodomains in Inorganic Lead Halide Perovskites.

Ultrastable CsPbBr3 nanoplates against electron beam irradiations are fabricated and nanodomains with anomalous high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) contrasts are observed within CsPbBr3 nanoplates. Atomic resolution energy dispersive X-ray spectroscopy (EDS) mapping, which requires even higher beam currents and may cause significant damages on electron beam sensitive materials, are obtained without any detectable damages or decomposition. Combining HAADF-STEM images, atomic resolution EDS mapping, and image simulations has revealed detailed structure and chemistry of the nanodomains to be induced by Ruddlesden-Popper faults (RP faults) rather than any chemical intermixing or formation of new phases. A formation mechanism is also proposed on the basis of the atomic structure of the nanodomains. This result promotes an atomic-level understanding of inorganic lead halide perovskites and may help to reveal their structure-property relationship.

Water-stable perovskite-loaded nanogels containing antioxidant property for highly sensitive and selective detection of roxithromycin in animal-derived food products

Luminescent inorganic lead halide perovskite nanoparticles lack stability in aqueous solutions, limiting their application to optical sensors. Here, hybrid CsPbBr3-loaded MIP nanogels were developed with enhanced stability in aqueous media. Multifunctional MIP nanogels with antioxidant function and hydrophobic cavities were synthesized from HEMA derivatives in the presence of roxithromycin as a template. The CsPbBr3 nanoparticles were loaded into pre-synthesized MIP nanogels via in-situ synthesis with a size distribution of 200 nm. The developed CsPbBr3-nanogel exhibits excellent stability to air/moisture and enhanced stability toward an aqueous solvent. The developed CsPbBr3-loaded MIP nanogels showed a selective and sensitive detection of ROX with a limit of detection calculated to be 1.7 × 10–5 μg/mL (20.6 pM). The developed CsPbBr3-loaded MIP antioxidant-nanogels were evaluated on practical application for the quantitative determination of ROX antibiotic in animal-derived food products with excellent analytical performance. The detection of ROX in animal-derived food products showed good recovery results, making them an ideal candidate for sensing ROX.

Temperature-Dependent Raman Studies of FAPbBr3 and MAPbBr3 Perovskites: Effect of Phase Transitions on Molecular Dynamics and Lattice Distortion

Three-dimensional hybrid organic–inorganic lead halide perovskites are promising photovoltaic and light-emitting materials. A key phenomenon relevant for their optoelectronic applications is electron–phonon coupling. Since it can be strongly modified by structural deformation and changes in the dynamics of molecular cations, it is of great importance to study the temperature dependence of phonon properties of hybrid perovskites. In this work, temperature-dependent Raman scattering studies of FAPbBr3 and MAPbBr3 single crystals are reported in the 1800–22 cm−1 and 300–90 K ranges. The Raman data of MAPbBr3 showed clear anomalies near 236, 155 and 148 K, which were attributed to Pm3¯m→I4/mcm→P4/mmm (or Imma)→Pnma phase transitions. They also provided strong evidence that crystal structure of the phase stable in the 155–148 K range is very similar to structure of the I4/mcm phase, not structure of the lowest-temperature Pmna phase, as suggested in some reports. Therefore, the symmetry of this phase seems to be more likely P4/mmm rather than Imma. An analysis of the temperature evolution of MAPbBr3 Raman modes revealed that the phase transitions near 236 and 155 K are associated with weak distortion of the inorganic subnetwork and changes in the dynamics of MA+ ions. Very pronounced changes in the lattice modes region and a narrowing of bands below 148 K indicated that the phase transition to the Pnma phase is triggered by a freezing of MA+ motions, which in turn leads to strong distortion of the inorganic subnetwork. Raman studies of FAPbBr3 showed that this material behaves in a very different way than MAPbBr3. First of all, the molecular dynamics of FA+ cations are not frozen even in the lowest-temperature Pnma phase. Moreover, the distortion of the inorganic subnetwork is small in the Pnma phase. The observation of weak anomalies in the lattice modes region confirmed, however, that the two crystallographically resolved phase transitions (Pm3¯m→P4/mbm near 260 K and P4/mbm→Pnma near 150 K) lead to weak distortion of the inorganic subnetwork. On the other hand, an analysis of FA+ internal modes indicated that these transitions, as well as two other crystallographically unresolved transitions near 120 and 180 K, are triggered by a change of FA+ dynamics.

Strain-induced electronic and optical properties of inorganic lead halide perovskites APbBr3 (A= Rb and Cs)

Recently, inorganic perovskite materials have been achieved with broad consideration in photovoltaic technology owing to their exceptional structural, electronic, and optical properties. This work comprehensively studied the impact of the biaxial compressive and tensile strain on the structural, electronic, and optical properties of the inorganic halide perovskites APbBr3 (A= Rb and Cs) using the first-principles density-functional theory (FP-DFT). This study also initiated to recognize the function of the A-cation on the structural, electronic, and optical properties of the inorganic perovskites. The electronic band structures show that RbPbBr3 and CsPbBr3 are semiconductor materials with a direct bandgap of 1.31 eV and 1.68 eV at the R-point. When considering the spin-orbital coupling (SOC) relativistic effect, the bandgap of the RbPbBr3 and CsPbBr3 perovskites is reduced to 0.282 and 0.478 eV, respectively. Moreover, the bandgap of all the structures shows a reducing trend when the compressive strain is applied and an increasing trend when the tensile strain is introduced. Optical properties like dielectric functions, absorption coefficient, and electron loss function show that these materials have good absorption ability in the visible region due to their band properties. It is found that the peaks of the dielectric constant of APbBr3 (A= Rb and Cs) shift to lower photon energy (redshift) when increasing compressive strain, and in contrast, they show higher photon energy shifting nature (blueshift) when enhancing tensile strain. Therefore, these properties make the APbBr3 (A= Rb and Cs) perovskites very appropriate to apply in light management of solar cells and energy storage devices.

Stokes Shift in Inorganic Lead Halide Perovskites: Current Status and Perspective.

Inorganic metal halide perovskite system is considered as a promising candidate for applications from display to biomedical industry. Intrinsic inorganic lead halides possess small Stokes shift or self‐absorption, providing negative impact for both photo voltaic and biomedical applications. Therefore, the development of an inorganic halide perovskite system with large Stokes shift is a significant venture. This review aims to provide an updated survey of the Stokes shift phenomena in the inorganic lead halide perovskites. The first section focuses about the mechanism, the second section gives different approaches in preparing inorganic perovskites with distinct Stokes shift, while the third section highlights the potential applications in both photovoltaic and biomedical areas. This review provides deep insight about the importance and usefulness of such phenomena in inorganic lead halides, essential for various applications.

Halide Perovskite Solar Cells for Building Integrated Photovoltaics: Transforming Building Façades into Power Generators.

The rapid emergence of organic-inorganic lead halide perovskites for low-cost and high-efficiency photovoltaics promises to impact new photovoltaic concepts. Their high power conversion efficiencies, ability to coat perovskite layers on glass via various scalable deposition techniques, excellent optoelectronic properties, and synthetic versatility for modulating transparency and color allow perovskite solar cells (PSCs) to be an ideal solution for building-integrated photovoltaics (BIPVs), which transforms windows or façades into electric power generators. In this review, the unique features and properties of PSCs for BIPV application are accessed. Device engineering and optical management strategies of active layers, interlayers, and electrodes for semitransparent, bifacial, and colorful PSCs are also discussed. The performance of PSCs under conditions that are relevant for BIPV such as different operational temperature, light intensity, and light incident angle are also reviewed. Recent outdoor stability testing of PSCs in different countries and other demonstration of scalability and deployment of PSCs are also spotlighted. Finally, the current challenges and future opportunities for realizing perovskite-based BIPV are discussed.

Synthesis and characterization of polypyrrole encapsulated formamidinium lead bromide crystals for fluorescence memory recovery

Impressive optical properties of organic–inorganic lead halide perovskite crystals make them suitable for optoelectronic devices. However, these crystals are unstable in water and other polar solvents and quickly lose their fluorescence which cannot be recovered by the addition of non-polar solvents. Fluorescence recovery is absolute necessity for long-term stability of perovskite in optoelectronic devices. Till date, there is no report showing mechanism of fluorescence recovery of organic–inorganic lead halide perovskite crystals. Here, we have reported the synthesis of FAPbBr3/polypyrrole (PPy) composites (FA = Formamidinium) for shedding light on the mechanism of fluorescence recovery in presence of N,N Dimethyl formamide or DMF. We have synthesized FAPbBr3 crystals at room temperature and tuned their band gap from green to blue by varying the amount of surfactant. Similar study was repeated with FAPbBr3/PPy composites, synthesized through in situ polymerization. Encapsulation was found to improve the emission quality and purity of the colour and successfully restored the fluorescence memory which was lost in presence of DMF. The recovery was attributed to resurfacing of PPy in presence of toluene which brought the building blocks of FAPbBr3 crystals back to the co-crystallization domain. In brief, this fundamental finding could pave the future way for achieving long-term stability of perovskite crystals in optoelectronic devices.

Characterization of a CH3NH3PbI3 perovskite microwire by Raman spectroscopy

AbstractWe investigated the structural properties of organic–inorganic lead halide perovskite microwires through joint experimental and theoretical Raman spectroscopy. High‐quality methyl ammonium lead iodide (MAPBI3, MA = CH3NH3+) microwires with tetragonal phases and explicit crystalline orientation were prepared. Raman spectroscopy was used in studying the as‐prepared microwires and determining not only the crystal quality but also crystalline orientation of MAPBI3 with the aid of normal mode calculations. High‐quality structural features were verified by well‐resolved Raman peaks related to the inorganic cage (IPbI stretching and bending modes below 100 cm−1), organic MA cation motions (libration ~150–200 cm−1 and torsional ~200–250 cm−1), a coupled mode of cage and MA cation liberation (~105–110 cm−1), and the almost undetectable degraded signal at 95 cm−1. In micro‐Raman mapping, an intensity ratio of 105 and 95 cm−1 was used for the direct imaging of crystal quality along the microwire. The characterization of the crystalline orientation of MAPBI3 microwires posed a challenge, which can be addressed by using polarized Raman technique with normal mode analysis. We believe that the proposed method can be extended to other organic–inorganic lead halide perovskites with different structures, such as polycrystalline films and single crystals.