Organic-inorganic Perovskite Materials Research Articles

Selection of the ultimate perovskite solar cell materials and fabrication processes towards its industrialization: A review

AbstractHybrid organic–inorganic perovskite materials have become one of the most studied classes of light‐harvesting materials due to their exceptional properties such as high light absorption, long carrier diffusion lengths, bandgap tuning and defect tolerance. Since 2009 that the scientific community has been working on improving the power conversion efficiency (PCE) of perovskite solar cell devices, reaching now an impressive value of 25.5%. Moreover, efficiencies over 18% are often reported by several authors. Since the efficiency goal is almost fulfilled, the scientific community is currently addressing five challenges, with the ultimate objective to make this technology competitive and turn it commercial; these challenges are cost, stability, upscaling, safety and environmental impact. Given the astonishing progresses reached during the past decade and the numerous research groups working to the same goal, it is a matter of time until commercial perovskite solar devices become a reality. In this review work, the most recent achievements regarding this purpose are put together and compared, so as to suggest the most suitable perovskite solar fabrication processes and materials to produce commercial devices.

Cation-Doping in Organic-Inorganic Perovskites to Improve the Structural Stability from Theoretical Prediction.

With outstanding photoelectric properties, organic-inorganic perovskites have become promising materials in the application of solar cells. However, their low stability limits their high conversion efficiency. On the basis of first-principles calculations, we screened out the optimal dopant into MAPbI3 from a variety of organic cations, and further revealed the mechanism underneath for the improved stability of cations doping. Our results have demonstrated that the doping of large-size cations (i.e., IPA+, TriMA+, and GA+) could efficiently inhibit the formation and diffusion of structural defects with high defect formation energies and large migration barriers, which is associated with the lattice expansion and greater hydrogen-bond formation. Our theoretical findings address crucial guidelines to design and synthesize the organic-inorganic perovskite materials with high stability, and provide valuable insights in understanding the stability mechanism, which may enhance the photovoltaic efficiency of perovskite materials and extend their wide applications.

Emission properties of sequentially deposited ultrathin CH3NH3PbI3/MoS2 heterostructures

Hybrid organic-inorganic perovskite materials have obtained considerable attention due to their exotic optoelectronic properties and extraordinarily high performance in photovoltaic devices. Herein, we successively converted the ultrathin PbI2/MoS2 into the CH3NH3PbI3/MoS2 heterostructures via CH3NH3I vapor processing. Atomic force microscopy (AFM)、Scanning electron microscopy (SEM) and X-ray photoemission spectroscopy (XPS) measurements prove the high-quality of the converted CH3NH3PbI3/MoS2. Both MoS2 and CH3NH3PbI3 related photoluminescence (PL) intensity quenching in CH3NH3PbI3/MoS2 implies a Type-II energy level alignment at the interface. Temperature-dependent PL measurements show that the emission peak position shifting trend of CH3NH3PbI3 is opposite to that of MoS2 (traditional semiconductors) due to the thermal expansion and electron-phonon coupling effects. The CH3NH3PbI3/TMDC heterostructures are useful in fabricating innovative devices for wider optoelectronic applications.

Surface interface structural studies of CH3NH3PbI3 thin films using synchrotron source X-ray diffraction for solar cell application

Presently, Organic-inorganic hybrid-based Perovskite material research is gaining attraction in the solar energy field, with efficiencies reaching upwards of 25.7 percent. Even though various efforts have been made to increase the shelf life and to reduce the degradation of perovskite material, still several complicated processes are required to achieve better structural properties and chemical stability. In this paper, Perovskite material is prepared with an optimized molar ratio (PbI2/MAI) = 1.0/1.0, this combination of PbI2 (Lead Iodide) and MAI (Methyl Ammonium Iodide) provides the best inter-diffusion (as noticed) and structural ordering. The above-stated ratio of PbI2 (Lead Iodide) and MAI (Methyl Ammonium Iodide) is suggested to be one of the best molar ratios in the literature. Except of this, there is still a lack of studies found in literature like the optimized structure properties for better device performance, as well as the thickness dependence structural properties variation and the role of inter-diffusion of MAI and PbI2. The present studies focused on the Synchrotron source-based X-ray Diffraction measurements to understand the structural properties of such films at the three different angles of incidence supported by SEM and AFM data. Finally, the present study of this perovskite material paves a way to understand the diffusion of MAI into the PbI2 along with the film thickness of 350 ± 50 nm of the Perovskite layer for one molar ratio in detail. Last but not the least, together with the Synchrotron source-based GIXRD measurements SEM, AFM, and UV–Vis spectroscopy helped to understand the distribution of PbI2 after MAI gets diffused into it and a little amount of un-used PbI2 leftover along with the entire film after the PbI2 and MAI Interaction.

Transition Metal Ions in Methylammonium Chloride Perovskites.

Organic–inorganic perovskite materials have become star materials for future wide band gap optoelectronics due to their excellent optical and electrical properties. However, the lead ions inside perovskites have become a crucial environmental issue in the commercialization of wide band gap perovskite devices . This research tries to find the structure and properties of lead-free perovskite materials by screening Sn2+ and transition-metal ions to replace Pb2+ within the methylammonium (MA)-based chloride perovskite and find out a new two-dimensional structure of MA-based transition-metal ion chlorides. Overall, MAZnCl3 may be a potential ultraviolet-C luminescent material with a stable two-dimensional structure with a wide band gap of 5.64 eV, which is suitable for ultraviolet-C luminescence applications.

Recent Advances in Tin-based Hybrid Organic-Inorganic PSCs: Additives for Improved Stability and Performance

Perovskite solar cells (PSCs) materials are progressing as potential candidates for the future generation of photovoltaics. Despite the most efficient photovoltaic performance, lead-based perovskite materials are not considered for commercialization due to the high toxicity of lead. One of the promising alternatives is tin (Sn)-based perovskites, which exhibits equivalent ionic size as lead and outstanding absorption properties. However, Sn-based perovskite materials have stability and low-performance issues because of the easy oxidation of Sn2+ to Sn4+and fast crystallization. This paper gives a focused overview of the notable recent studies to address the stability and low-performance challenges of Sn-based hybrid organic-inorganic perovskite (Sn-HOIP) materials for solar cells by using functional additives. To date, the addition of SnF2 additive in the methylammonium tin iodide-based PSCs has shown the highest efficiency of 7.78% and maintains 70% of original efficiency over 200-hours. In the case of formamidinium tin iodide-based PSCs, the addition of phenylhydrazine hydrochloride significantly increases the power conversion efficiency to 11.40% from 5.60% for a pristine device. However, further improvement in the stability and efficiency of Sn-based PSCs requires a molecular-level understanding of the role of existing and new candidates of additives tailored for evolving Sn-HOIP materials.

Bayesian Estimation of Equivalent Circuit Parameters of Photovoltaic Cell with S‐Shaped Current–Voltage Characteristic

An S‐shaped current–voltage characteristic is frequently observed in a photovoltaic cell using emerging materials such as organic semiconductors and organic–inorganic perovskite materials. The opposed two‐diode equivalent circuit model, whose explicit analytical solution is known, can reproduce the S‐shaped characteristic. However, since the number of parameters is as high as eight, it is not easy to extract the equivalent circuit parameters from experimental data by curve fitting. Herein, the Bayesian estimation in extracting the equivalent circuit parameters of the opposed two‐diode model is demonstrated. Unlike the traditional nonlinear least‐squares method, the Bayesian estimation practically does not require any tuning of the initial values and gives the information on the error of the estimates.

Theoretical Investigation of Organohalide Perovskite Degradation in Water

Methylammonium lead iodide (CH3NH3PbI3) is an extensively used organic-inorganic perovskite material with a remarkable potential for solar energy conversion. Despite its high photovoltaic efficiency, it suffers from fast degradation in humid air atmospheric working environments. Low stability of CH3NH3PbI3 solar cells in humid air environments is a serious drawback, severely limiting their practical application. Protecting organohalide perovskite thin films from water and ambient humidity represents a paramount challenge, in which the interfacial interactions between CH3NH3PbI3 surface and water molecules need to be understood thoroughly. Here, we present ab initio molecular dynamics simulations aimed at investigating interfacial interactions between the CH3NH3PbI3 perovskite of different surfaces and water molecules. We harness enhanced free-energy sampling techniques to simulate CH3NH3PbI3 degradation with explicit treatment of water molecules to examine the degradation kinetics. The degradation energetics from different CH3NH3PbI3 surfaces along with the effect of various type of defects in the material are also explored. Our findings add a comprehensive mechanistic understanding to the state of knowledge of CH3NH3PbI3 degradation mechanisms in humid air. The presentation will close with a discussion of similar stability predictions on other organohalide perovskite materials.

Temperature dependent phase transitions and their relation to isosbestic point formation. Case study of C(NH2)3PbI3

Besides the vast research regarding the hybrid organic-inorganic perovskite (HOIP) materials used in the solar cell production, their properties are still not fully uncovered. In this paper, detailed investigation on the phase transitions in guanidinium lead iodide (GAPbI3) using vibrational spectroscopy techniques (IR and Raman) are presented. In addition to the well-known three phases of GAPbI3 (denoted as I, II and III) another one existing in the temperature range from 48 °C to 160 °C is characterized. The thorough inspection of the vibrational spectra revealed some interesting changes occurring in the low temperature region (from −90 to −62 °C) that suggest presence of a new phase. Finally, a redefinition of the phase nomenclature according to the recommendations given by the IUCr is proposed.

A hybrid organic-inorganic perovskite with robust SHG switching

Owing to the diversity of structure and potential applications in the field of electrics, sensors, and light-emitting diodes, lead halide perovskites have attracted great attention in recent years. Especially those lead halide perovskites with non-centrosymmetric crystal structures usually exhibit nonlinear optical (NLO) characteristics, which may endow them photoelectricity switching functionality. In this work, a lead-based hybrid organic-inorganic perovskite (HOIP) material, trimethyliodomethylammonium lead trichloride (TMIM·PbCl3), is obtained on the basis of tetramethylammonium lead chloride through halogen substitution on the cation part. It shows dual-phase-transition behavior around 345 and 358 K, which is significantly improved. TMIM·PbCl3 crystallizes in the chiral space group, P212121, and shows a well-defined second harmonic generation (SHG) response, and good switching endurance, which makes it an excellent candidate for SHG switching material. This work highlights the importance of halogen substitution for crystal engineering and may pave way for the further exploration of the optoelectronic devices.

Guanidinium cation passivated Pb-Cu alloyed perovskite for efficient low-toxicity solar cells

Overcoming the toxicity of organic–inorganic perovskite materials is one of the main challenges in applying them to commercial optoelectronic devices, despite the amazing power conversion efficiency (PCE) of organic–inorganic hybrid perovskite solar cells (PSCs). In this work, we demonstrate a low-toxicity Pb-Cu alloyed perovskite film prepared by simple two-step methods and its integration in inverted PSCs. The formation of iodine defects was suppressed through the hydrogen bonding of guanidinium (Gua) cation (CH6N3+), which greatly improves the quality of the film. It is demonstrated that introduction of GuaI additives leads to stronger photoluminescence (PL) intensity, and lower defects state density. The open circuit voltage (Voc) and PCE of Pb-Cu alloyed PSCs reached 0.95 V and 9.69%, respectively. This work helps to guide the preparation of efficient low-toxicity Pb-Cu alloyed optoelectronic devices.

Emergence of bulk photovoltaic effect in anion-ordered perovskite sulfur diiodide MASbSI2 with spontaneous out-of-plane ferroelectricity

Organic-inorganic halide perovskites composed of three-dimensional (3D) corner-sharing octahedral framework, represented by methylammonium lead iodide MAPbI3, have attracted extensive research interests owing to their superior photovoltaic (PV) performance. On the other hand, taking advantage of spontaneous ferroelectricity and the associated bulk photovoltaic effect (BPVE), ferroelectric (FE)-PV materials are able to generate zero-bias photocurrent and above band gap photovoltage, offering the great promise for improved power conversion efficiency. However, FE nature of perovskite MAPbI3 remains controversial. Alternatively, heteroanionic perovskite where the multiple anions of distinct sizes and valence states are in ordered arrangement, can create polar crystal structures with permanent electric polarization. In current work, we choose the experimentally reported perovskite methylammonium antimony sulfur diiodide MASbSI2 as a prototypical example, and demonstrate trans S/I anion order and the stable out-of-plane ferroelectricity nearly independent of molecular dipoles from organic MA cations can be obtained in such a 3D organic-inorganic heteroanionic perovskite by first-principles calculations. The cooperative interplay of MA orientation, octahedral rotation, cation polar displacement and S/I anion arrangement that govern the origin and magnitude of ferroelectricity within MASbSI2 have been thoroughly explored and well rationalized by our comprehensive first-principles calculations and electrostatic bond strength sum analysis. Especially, based on our electronic structure and nonlinear photo-current responses simulations, FE perovskite MASbSI2 with combination of stable out-of-plane ferroelectricity up to 17.9 μC/cm2, tunable semiconducting band gap, static Rashba effect and polarization controllable strong photocurrent responses within the visible light range, is demonstrated to be a long-sought 3D FE organic-inorganic perovskite material for efficient light-current conversion through BPVE.

Shaping Perovskites: In Situ Crystallization Mechanism of Rapid Thermally Annealed, Prepatterned Perovskite Films.

Understanding and controlling the crystallization of organic–inorganic perovskite materials is important for their function in optoelectronic applications. This control is particularly delicate in scalable single-step thermal annealing methods. In this work, the crystallization mechanisms of flash infrared-annealed perovskite films, grown on substrates with lithographically patterned Au nucleation seeds, are investigated. The patterning enables the in situ observation to study the crystallization kinetics and the precise control of the perovskite nucleation and domain growth, while retaining the characteristic polycrystalline micromorphology with larger crystallites at the boundaries of the crystal domains, as shown by electron backscattering diffraction. Time-resolved photoluminescence measurements reveal longer charge carrier lifetimes in regions with large crystallites on the domain boundaries, relative to the domain interior. By increasing the nucleation site density, the proportion of larger crystallites is increased. This study shows that the combination of rapid thermal annealing with nucleation control is a promising approach to improve perovskite crystallinity and thereby ultimately the performance of optoelectronic devices.

Observing and Understanding the Corrosion of Silver Nanowire Electrode by Precursor Reagents and MAPbI3 Film in Different Environmental Conditions

AbstractSince metal electrode is an important component in the perovskite solar cells, which can be used as back contact, transparent electrode, and the transparent interlayer of tandem devices, the corrosion of metal electrode by perovskite film, should be understood. Here, the corrosion of conventional reagents of organic–inorganic perovskite material, i.e., CH3NH3X (MAX) and PbX2, X = I, Br, and Cl, against silver nanowire (AgNW) based transparent electrode are investigated under four different environments, i.e., nitrogen protection, light irradiation, oxygen exposure, and moisture exposure, separately. The corrosion process is inspected by monitoring the time‐dependent resistance variation of the electrode coated by the film of precursor reagent. In addition, the perovskite film of CH3NH3PbI3 (MAPbI3) is also coated on the silver nanowire electrode without or with the hole transporting layer of poly(3,4‐ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT:PSS) or nanostructured CuSCN for understanding the corrosion process under different environmental conditions. The experimental results presented in this paper would be helpful to the understanding of metal electrode stability in perovskite solar cells.

The development of a neural network model for the structural improvement of perovskite solar cells using an evolutionary particle swarm optimization algorithm

The revolution represented by third-generation photovoltaic devices relied on the discovery of various hybrid organic–inorganic perovskite materials to convert solar into electrical energy. One of the advantages of such cells is their low cost due to the raw materials and cheap production methods used. Nevertheless, these cells face several challenges, such as inadequate stability and the hysteresis phenomenon. To overcome these, perovskite solar cell (PSCs) with planar and inverted structures have been utilized with an inorganic hole transport layer (HTL), achieving acceptable efficiency. As there is no closed-form system of equations to describe the operation of such cells, neural networks have been employed for their modeling. In optimization algorithms, the values of the parameters must be swept, since most current simulation tools cannot use them directly. Such software optimization can notably decrease the cost of cell design. This paper presents a practical way to achieve the mentioned aim. In particular, an artificial neural network (ANN) is exploited for the modeling, then an evolutionary particle swarm optimization (E-PSO) algorithm is developed to optimize the structure to achieve the highest efficiency based on searching the energy conversion. The results of the simulations are then employed in SCAPS software to train the neural network. This optimization leads to the achievement of an efficiency of 23.76% for the proposed structure, better than values reported in literature.

Solvent engineering of lead-free bismuth-based perovskite material for potential application of solar cell

In the past few years, hybrid organic–inorganic perovskite materials have attracted great attention due to their impressive properties for solar cells applications. However, perovskite methylammonium lead halide is facing with toxicity issues that may hinder the wide range application of the lead halide-based hybrid perovskite solar cells. The sources of toxicity of these solar cells are the pollution from the B-site of lead ion and the toxic solvents used in the fabricating the devices. Thus, environmentally friendly materials and non-toxic solvents are highly desired for large-scale manufacturing of perovskite solar cells. In this work, the chemical and optical properties of lead-free bismuth based MA3Bi2I9 perovskite fabricated using different compositions of non-toxic solvents are investigated through solvent engineering method. Dimethyl sulfoxide (DMSO) /acetonitrile (ACN) /methyl-acetate (MA) solvents were employed as non-toxic solvent systems for the formation of homogeneous and good quality perovskite film. Hybrid organic–inorganic lead-free perovskite films were fabricated by mixing 1:1 M ratio compositions of CH3NH3I and BiI3 in different mixture of the solvents. The results show that the mixing solvent DMSO / ACN / MA at a volume ratio of 5:2:3 v / v, which incorporates the advantages of each solvent, has the best result among others. It is believed that by optimizing the solvent compositions, high performance lead-free bismuth-based perovskite film using non-toxic solvents could be obtained for potential solar cells application.

Effect of methylammonium lead tribromide perovskite based-photoconductor under gamma photons radiation

Organic-inorganic perovskite materials are successfully employed for optoelectronics (UV–Visible photodetector and solar cell) and ionization radiation detector. The radiation hardness is a key issue for ionization applications based on perovskite materials. Here, the radiation effect on optical, structural and electrical properties of methylamine bromide (CH3NH3PbBr3) single crystals under high dose gamma photons are systematically investigated. It is demonstrated from the X-ray diffraction pattern and surface morphologies that single crystals are evenly divided into several pieces after receiving an accumulative dose of 16.56 kGy. The transmittances significantly decrease with increasing the irradiation dose. It is shown from the photoluminescence spectroscopy that sub-bandgap emission is present after irradiation. The sensitivity of CH3NH3PbBr3-based photoconductor improves about tenfold after irradiation at 5.52 kGy, and the highest sensitivity is 1.12 mC Gy−1 cm−2 when the applied voltage is 4 V. This phenomenon of improving the electrical properties of the crystal after gamma-ray irradiation is correlated with decomposition and self-healing behavior.

Unraveling the Impact of Halide Mixing on Crystallization and Phase Evolution in CsPbX3 Perovskite Solar Cells

Summary All-inorganic perovskite solar cells (PSCs) have attracted wide attention for their excellent thermal stability. However, the detailed crystallization process and complicated phase-transition mechanism of the CsPbX3 film with different halide compositions (I, Br, Cl) remain mysterious. In this study, systematic investigations are performed via state-of-art in situ grazing-incidence wide-angle X-ray scattering to understand the role of the halide elements in all-inorganic perovskite crystallization kinetics, phase-transition, and stabilization mechanism as well as how film morphology and grain size are affected. Based on these results, we were able to fabricate high-performance ternary halide (I, Br, Cl) all-inorganic PSCs through a precise compositional engineering. Our results provide guidance for an in-depth understanding of all-inorganic perovskite materials and pave the way to obtain high-performance all-inorganic PSCs.

The compositional engineering of organic–inorganic hybrid perovskites for high-performance perovskite solar cells

In the last decade, organic–inorganic perovskite materials have drawn great attentions in both academic and industrial sectors because of their remarkable optoelectronic and photovoltaic properties. Various perovskite materials have been investigated for high-performance perovskite solar cells. In this short review, we aim to illustrate optimized photovoltaic properties of perovskite materials through compositional engineering of organic–inorganic hybrid perovskite materials. We firstly elaborate the progresses of compositional engineering for each of three components in AMX3 perovskite materials, and then highlight the optoelectronic and photovoltaic properties of the resultant perovskite materials. It was found that the compositional engineering of organic–inorganic hybrid perovskites plays an important role in device performance of perovskite solar cells. Lastly, the outlook and prospects of compositional engineering of organic–inorganic hybrid perovskite materials are briefly discussed.

Investigation of air-stable Cs2SnI6 films prepared by the modified two-step process for lead-free perovskite solar cells

In recent years, the organic-inorganic perovskite materials have revolutionized the Photovoltaic industry with highly efficient power conversion devices accompanied by a high growth rate. However, these devices experience major environmental and stability issues that hinder their true potential. More recently, a rarely studied perovskite material Cs2SnI6 is gaining enormous attention due to its superior stability and suitable bandgap. In this work, we developed a modified two-step process to prepare uniform Cs2SnI6 films, and the influence of the reaction conditions on the properties is explored. The structural, morphological, optical, and electrical properties of the prepared films were investigated using x-ray diffraction, Raman spectroscopy, scanning electron microscopy, UV–vis spectrometer, photoluminescence, and Hall Effect measurements, respectively. Phase stability and morphology of the films are improved with optimizing the reaction conditions. The results confirm the n-type semiconductor nature of Cs2SnI6 with bandgap ranging from 1.29 eV to 1.42 eV with maximum carrier mobility of 425 cm2 V−1 s−1. The present study will further provide potential research directions in improving the device efficiency of air-stable Cs2SnI6 perovskite solar cells.