Organic-inorganic Hybrid Perovskite Materials Research Articles

Effects of valence changes of iodine on perovskite (CH3NH3PbI3) Raman

In recent years, organic–inorganic hybrid perovskite materials have garnered extensive attention from scholars. Given its high absorption coefficient, carrier mobility, and diffusion length, it is widely studied for applications in various optoelectronic devices, such as solar cells, photodetectors, field-effect transistors, and light emitting diodes. Among them, the interfacial charge transfer process is a key factor influencing the performance of devices using perovskite materials. The charge transfer (CT) at the interface is typically detected via Raman spectroscopy. There are three types of related CT processes, namely, the interfacial ground state charge transfer, the photoinduced charge transfer resonance, and the electronic excitation resonance within the molecule itself. Among these factors, electronic excitation resonance manifests as an exciton resonance within the perovskite structure, providing energy for nearby charge transfer, thereby promoting charge transfer and enhancing Raman signals. Therefore, enhancing exciton resonance within the perovskite structure plays a crucial role in optoelectronic devices. This paper aimed to study the mechanism of oxygen plasma passivation of interstitial iodine defects and its enhancement effect on the Raman of perovskite substrates. Typically, interstitial iodine defects induce electron–hole recombination. In the process of oxygen plasma treatment, interstitial iodine is converted into pentavalent iodine, which can effectively fill related defects, inhibit electron–hole recombination, and prolong exciton lifetime, thereby promoting charge transfer and enhancing Raman intensity.

MAPbI3 perovskite photodetectors for high-performance optical wireless communication

High-sensitivity and fast-response photodetectors (PDs) are vital part of optical wireless communication (OWC) system. In this work, we develop an organic–inorganic hybrid perovskite material (MAPbI3) based p–i–n structured PD. By optimizing the precursor solution concertation, the PD showed a high responsivity of 0.98 A W−1, a fast response time t rise/t fall of 12/12.5 μs, a specific detectivity of 2.62 × 1013 Jones, and the f−3dB of 24 kHz under the 532 nm laser and −0.2 V bias voltage. Furthermore, we designed an OWC system based on the prepared PD. With the baud rate of 19200 bps, the system exhibits a bit error rate less than 10−6, and it can realize 9.63 m long-distance communication and quick transmission applications such as strings, texts, photos, and audios. Our work demonstrates the great application potential of perovskite PDs in the field of optical communication.

Structural phase transition in a new organic-inorganic hybrid post-perovskite: (N,N-dimethylpyrrolidinium)[Mn(N(CN)2)3]

In the realm of molecular phase transition research, particularly for applications in sensors, data storage and switching technologies, the role of organic-inorganic hybrid perovskite materials has been increasingly recognized for their significant potential. Nevertheless, hybrid post-perovskites, as a critical subclass of perovskites, have not been thoroughly studied and mainly limit in the instances based on polyatomic bridging agents like dicyanamide (dca−) and non-cyclic organic cations. Herein, a polar cyclic quaternary ammonium cation, N,N-dimethylpyrrolidinium (DMP+), was used to assemble a new hybrid post-perovskite, (DMP)[Mn(dca)3] (1), which undergoes a phase transition from orthorhombic Bmmb to monoclinic P21/n space group at 249 K. By employing multiple techniques such as differential scanning calorimetry, variable-temperature single-crystal X-ray analysis, dielectric measurements, and Hirshfeld surface analysis, we disclosed the role of polar cyclic quaternary ammonium DMP+ in elevating the phase-transition temperature by 48 K, generating significant dielectric switching effect, and facilitating interlayer sliding of inorganic framework.

THz‐Wave Absorption Properties of Organic–Inorganic Hybrid Perovskite Materials: A New Candidate for THz Sensors

Over the past two decades, organic–inorganic hybrid perovskite materials (OHP) have been extensively explored across various scientific disciplines, including physics, chemistry, and materials science, with a primary focus on solar cells. Building on numerous studies, the development of OHP‐based solar cells has transitioned into practical product realization, instilling the anticipation of novel solar cell advancements. Notably, OHP demonstrates versatility beyond its conventional application in solar cell materials. The physical properties of OHP materials exhibit a unique signature, thereby underscoring their potential utility as innovative functional materials, encompassing light‐emitting diodes, lasers, and photodetectors. Recent reports on terahertz (THz)‐wave absorption properties of OHP materials indicate a high possibility of their potential application as THz sensors. From the viewpoint of medical devices, which hold the most promising application potential, the exploration of optical phonon vibrational modes in the 0.5–3 THz frequency range is important. Moreover, understanding the correlations between atomic structure and lattice vibration modes is indispensable. In this concise review, the THz‐wave absorption properties exhibited by 3D OHP materials are meticulously explored. Furthermore, future research directions for THz sensors using OHP materials are suggested.

Tunable Periodic Nanopillar Array for MAPbI3 Perovskite Photodetectors with Improved Light Absorption.

In the field of optoelectronic applications, the vigorous development of organic-inorganic hybrid perovskite materials, such as methylammonium lead triiodide (MAPbI3), has spurred continuous research on methods to enhance the photodetection performance. Periodic nanoarrays can effectively improve the light absorption of perovskite thin films. However, there are still challenges in fabricating tunable periodic patterned and large-area perovskite nanoarrays. In this study, we present a cost-effective and facile approach utilizing nanosphere lithography and dry etching techniques to create a large-area Si nanopillar array, which is employed for patterning MAPbI3 thin films. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) results reveal that the introduction of nanopillar structures did not have a significant adverse effect on the crystallinity of the MAPbI3 thin film. Light absorption tests and optical simulations indicate that the nanopillar array enhances the light intensity within the perovskite films, leading to photodetectors with a responsivity of 11.2 A/W and a detectivity of 7.3 × 1010 Jones at 450 nm in wavelength. Compared with photodetectors without nanostructures, these photodetectors exhibit better visible light absorption. Finally, we demonstrate the application of these photodetector arrays in a prototype image sensor.

Interface-Tension-Assisted Temperature-Gradient Crystallization of High-Quality MAPbBr3 Perovskite Single Crystals with Low Defect Densities.

Comprehensive understanding and precise manipulation of the crystallization process for organic-inorganic hybrid perovskite materials are crucial for advancing perovskite single-crystal optoelectronic technology. In this study, we theoretically and experimentally investigated the influence of interface tension on the synthesis of perovskite single crystals. On the basis of the understanding of the nucleation and growth mechanisms, we developed a polydimethylsiloxane-assisted temperature-gradient growth technique to prepare high-quality MAPbBr3 single crystals. Using this technique, we harvested some high-quality MAPbBr3 single crystals, with the narrowest reported full width at half-maximum (0.00806°) of X-ray diffraction rocking curve, the longest carrier lifetime of 1002 ns, and an ultralow trap-state density of 4.25 × 109 cm-3. Furthermore, the X-ray detector fabricated using our MAPbBr3 single crystal exhibited a high sensitivity of 7275 μC Gy1- cm2 and a low minimum detection limit of 0.67 μGy s-1. This paper presents a novel method to control the crystallization and growth processes of high-quality perovskite single crystals.

Bottom interface passivation with benzylamine thiocyanate for improving the performance of inverted perovskite solar cells

The organic–inorganic hybrid perovskite materials have attracted a lot of attention in the photovoltaics field due to their excellent photovoltaic properties and simple preparation process in recent years. The well-known hole transport layer PTAA in the inverted perovskite solar cells (PSCs) is prone to trigging the nonradiative recombination and limiting the device performance. Here, we added benzylamine thiocyanate (BnASCN) bottom interface passivation layer between PTAA/perovskite layers to regulate the crystal growth of perovskite film, thus increase the grain size of perovskite film. The amino-passivation of BnA+ and the interaction of the strongly electronegative S and N in pseudo-halogens with the undercoordinated Pb2+, the defect density of the perovskite films is reduced, which effectively reduced the nonradiative recombination and inhibited ion migration, and the device power conversion efficiency improved from 17.12 % to 19.48 %. Moreover, the stability of the device is improved.

Polymer Backbone Stabilized Methylammonium Lead Bromide Perovskite Nano Islands.

Organic-inorganic hybrid perovskite materials continue to attract significant interest due to their optoelectronic application. However, the degradation phenomenon associated with hybrid structures remains a challenging aspect of commercialization. To overcome the stability issue, we have assembled the methylammonium lead bromide nano islands (MNIs) on the backbone of poly-3-dodecyl-thiophene (PDT) for the first time. The structural and morphological properties of the MNI-PDT composite were confirmed with the aid of X-ray diffraction (XRD) studies, Field emission scanning electron microscope (FESEM), and X-ray photoelectron spectroscopy (XPS). The optical properties, namely absorption studies, were carried out by ultraviolet-visible spectroscopy. The fluorescent behavior is determined by photoluminescence (PL) spectroscopy. The emission peak for the MNI-PDT was observed at 536 nm. The morphology studies supported by FESEM indicated that the nano islands are completely covered on the surface of the polymer backbone, making the hybrid (MNI-PDT) stable under environmental conditions for three months. The interfacial interaction strategy developed in the present work will provide a new approach for the stabilization of hybrids for a longer time duration.

Indoor bifacial perovskite photovoltaics: Efficient energy harvesting from artificial light sources

Emerging bifacial photovoltaics (BPVs) have received tremendous attention due to their high efficacy and economical cost by harvesting more light energy in outdoor conditions. Although, the performance of BPVs in outdoor conditions is severely limited by the albedo light (light reflected from the surface, soil, clouds, etc.). Conversely, BPVs could also be utilize to efficiently harvest energy from indoor environments such as offices, homes, large gathering halls, stations, and more, where multiple artificial lighting sources are employed. In this work, we have designed an efficient indoor bifacial perovskite photovoltaics (i-BPPVs) with the capability of harvesting maximum light from both top and bottom sides. The i-BPPVs were designed and fabricated in a stack of organic–inorganic hybrid perovskite material amid a transparent bottom electrode (ITO), and top (Au/ITO) electrode. The fabricated i-BPPVs exhibited an efficiency of 30.3%, short circuit current density (JSC) of 148.3 µA cm−2, open circuit voltage (VOC) of 0.93 V, and fill factor (FF) of 71.7% when artificial LED light source of 1000 lx is exposed from the top side, whereas an efficiency of 22.1%, JSC of 116.2 µA cm−2, VOC of 0.89 V, and FF of 69.4% have been obtained from the bottom side. The champion bifacial i-BPPVs display an excellent bifaciality factor (Φ) of 0.73 and demonstrated superior operational stability when subjected to continuous illumination. Moreover, this work of designing i-BPPVs will be a pivotal step towards advancing cost-effective and efficient technology for harvesting more energy from artificial indoor light sources.

A Two-Dimensional Hybrid Lead Bromide Ferroelectric Semiconductor with an Out-of-Plane Polarization.

A two-dimensional (2D) organic-inorganic hybrid perovskite (OIHP) material with out-of-plane ferroelectricity is the key to the miniaturization of vertical-sandwich-type ferroelectric optoelectronic devices. However, 2D OIHP ferroelectrics with out-of-plane polarization are still scarce, and effective design strategies are lacking. Herein, we report a novel 2D Dion-Jacobson perovskite ferroelectric semiconductor synthesized by a rigid-to-flexible cationic tailoring strategy, achieving an out-of-plane polarization of 1.7 μC/cm2 and high photoresponse. Integrating out-of-plane ferroelectricity with excellent photoelectric properties affords a promising platform to investigate ferroelectricity-related effects in vertical optoelectronic devices.

Advances to Stabilize Photoactive Phase of FAPbI3 Perovskite†

Comprehensive SummaryRecently, hybrid organic–inorganic perovskite materials have drawn widespread attention because of their outstanding optoelectrical properties (i.e., high absorption coefficient, long carrier diffusion distance), hence they are suitable light‐absorbing materials for photovoltaic application. Among all perovskite materials, formamidinium lead iodide (FAPbI3) based solar cells exhibit impressive power conversion efficiency (PCE) at laboratory stage, showing great potential to compete with silicon‐based solar cell. However, FAPbI3 still suffers from poor phase stability which is the prior problem that needs to be addressed before its further commercialization. To be precise, the photoactive phase (α phase) is thermodynamically metastable at room temperature, which not only makes α phase tend to transform into photoinactive phase (δ phase), but also causes competitive crystallization between two phases during the film preparation process, making it hard to fabricate pure α‐FAPbI3 films. In our review, we summarized key factors that are vital for obtaining high‐quality FAPbI3 perovskite thin films and enhancing the stability of FAPbI3 photoactive phase. First of all, precursor solution stability is of great importance since the conditions of precursor solution determine the nucleation and crystal growth process of perovskite. By introducing coordinating additives, using FAPbI3 single crystal as raw material or applying co‐solution strategy, the impurities formed by side reaction during precursor solution aging can be effectively suppressed, thus the stability of FAPbI3 solution can be greatly prolonged. Second, the crystallization kinetics of FAPbI3 have been systematically manipulated to obtain dense and large grain size perovskite films. Through introducing intermediate phase, regulating the surface energy, and retarding the crystal growth of FAPbI3 in crystallization process, not only films without pinholes and fewer grain boundaries can be obtained, the pre‐formed δ phase at room temperature can also be well‐suppressed, thus high‐quality α‐FAPbI3 films can be obtained. Third, how to thermodynamically enhance the phase stability of acquired FAPbI3 film has been extensively studied. The Gibbs free energy of FAPbI3 photoactive phase can be reduced through composition engineering, dimension engineering and external additives engineering, hence the phase transition barrier from α phase to δ phase has been significantly improved, which further enhance the phase stability of α‐FAPbI3. Lastly, we pointed out challenges of each method and proposed potential applications of mentioned strategies on improving the stability of all kinds of perovskite materials, thus further boost the commercialization of perovskite solar cell devices.

Understanding optical and structural properties of the CH3NH3PbI3 nanocrystal thin films under humidity conditions

Low-dimensional organic-inorganic hybrid perovskite materials have drawn a lot of interest in optoelectronic applications because of their unique optoelectronic performance in comparison to their bulk counterparts. There is an influence of humidity conditions on the stability of perovskite in both positive and negative ways. The passivation of surface and bulk defects in the thin film of perovskite by the H2O molecules is a positive way. The negative way is that the material's stability will hinder the commercialization of perovskite-based devices. Herein, CH3NH3PbI3 nanocrystals are synthesized by the hot-injection method. The optical and structural properties of the thin film of the synthesized nanocrystals under different humidity conditions are studied through photoluminescence (PL), TRPL, Raman, X-ray diffraction (XRD), UV–Vis, spectroscopic ellipsometry, and FTIR techniques for 4 weeks. The redshift in the PL spectra of the thin film with an increase in PL intensity and carrier lifetime is caused by the shallow trap-assisted radiative recombination and localization of the charge carriers at the interface of the CH3NH3PbI3/water. The XRD, Raman, and FTIR peaks of the thin film are also shifted due to defect formation and structure distortion of the CH3NH3PbI3 crystal lattice. The thin films of these nanocrystals exhibit very high PLQY of 56% and 60% after 5 h and 1 week respectively. The results pave the way to analyse the stability of CH3NH3PbI3 nanocrystals through their optical and structural behaviour under different humidity conditions. The results also reflect that the photoemission of the synthesized material can be tuned by regulating the defect density and the structural deformation of the nanocrystals under controlled humidity conditions.

Synthesis of Organic-Inorganic Hybrid Perovskite/MOF Composites from Pb-MOF Using a Mechanochemical Method.

The specific structure and diverse properties of hybrid organic-inorganic perovskite materials make them suitable for use in photovoltaic and sensing fields. In this study, environmentally stable organic-inorganic hybrid perovskite luminescent materials using Pb-MOF as a particular lead source were prepared using a mechanochemical method. Based on the fluorescence intensity of the MAPbBr3/MOF composite, the mechanized chemical preparation conditions of Pb-MOF were optimized using response surface methodology. Then, the morphological characteristics of the MAPbBr3/MOF composite at different stages were analyzed using electron microscopy to explore its transformation and growth process. Furthermore, the composite form of MAPbBr3 with Pb-MOF was studied using XRD and XPS, and the approximate content of MAPbBr3 in the composite material was calculated. Benefiting from the increase in reaction sites generated from the crush of Pb-MOF during mechanical grinding, more MAPbBr3 was generated with a particle size of approximately 5.2 nm, although the morphology of the composite was significantly different from the initial Pb-MOF. Optimal performance of MAPbBr3/MOF was obtained from Pb-MOF prepared under solvent-free conditions, with a milling time of 30 min, milling frequency of 30 Hz and ball-material of 35:1. It was also confirmed that the mechanochemical method had a good universality in preparing organic-inorganic hybrid perovskite/MOF composites.

Atomic-Scale Imaging of Organic-Inorganic Hybrid Perovskite Using Transmission Electron Microscope

Transmission electron microscope (TEM) is thought as one powerful tool to imaging the atomic-level structure of organic inorganic hybrid perovskite (OIHP) materials, which provides valuable and essential guidance toward high performance OIHP-related devices. However, these OIHPs exhibit poor electron beam stability, severely limiting their practical applications in TEM. Here in this article, the application of TEM to obtain atomic-scale image of OIHPs, main obstacles in identifying the degradation product and future prospects of TEM in the characterization of OIHP materials are reviewed and presented. Three potential strategies (sample protection, low temperature technology, and low-dose technologies) are also proposed to overcome the current drawback of TEM technology.

Surface passivation by CTAB toward highly efficient and stable perovskite solar cells

Organic–inorganic hybrid perovskite materials with mixed organic cations (FAxMA(1-x)PbI3) have attracted intensive attention due to their superior optoelectronic properties. In this work, the FA0.3MA0.7PbI3 perovskite film were synthesized and applied in perovskite solar cells (PSCs) based on carbon counter electrode (CCE). And a passivation approach for the perovskite/CCE interface is presented, using cetyltrimethylammonium bromide (CTAB). The quaternary amine and bromine ion of CTAB can fill the vacancy defects of FA/MA and iodine ion, respectively, leading to a more hydrophobic and smoother surface than the untreated film. The optimum device based on 0.5 mg/ml CTAB exhibited an short-circuit current density of 23.68 mA·cm−2 with a power conversion efficiency of 12.69%, which is superior to PSCs without CTAB. The long-term stability test in ambient atmosphere with 40% relative humidity reveals the higher stability of PSCs with the surface passivation, which is favorable for its commercial application.

Using Imidazolium in the Construction of Hybrid 2D and 3D Lead Bromide Pseudoperovskites

The field of hybrid organic–inorganic perovskite materials continues to attract the interest of the scientific community due to their fascinating properties and the plethora of promising applications in photovoltaic and optoelectronic devices. To enhance the efficiency and stability of perovskite-based devices, it is essential to discover novel compounds but also to investigate their various physicochemical, structural, and thermal properties. In this work, we report the synthesis and structural characterization of two novel hybrid lead bromide perovskites, combining the imidazolium cation (IMI) with methylammonium (MA) or formamidinium (FA) cations. The isolated polycrystalline powders were studied with X-ray powder diffraction (XPRD) and were formulated as (IMI)(MA)Pb2Br6, a 3D structure consisting of dimers of face-sharing octahedra linked in corner-sharing mode, and (IMI)(FA)PbBr4, a 2D (110) oriented layer structure with zig-zag corner-sharing octahedra. The thermal stability of (IMI)(MA)Pb2Br6 and (IMI)(FA)PbBr4 was investigated with thermogravimetric (TG) and differential scanning calorimetry (DSC) experiments which showed that both compounds are chemically stable (at least) up to 250 °C. Variable-temperature X-ray diffractometric (VT-XRD) studies of (IMI)(FA)PbBr4 highlighted a structural modification occurring above 100 °C, that is a phase transformation from triclinic to orthorhombic, via an elusive monoclinic phase.

Recent trend of using computational science tools in organic-inorganic hybrid perovskite materials research

Organic-inorganic hybrid perovskite materials have been considered promising candidates for solar cells in the future, and computational science tools have been widely used in the research on the structure and various properties of these perovskite materials. Researchers have also focused on finding the composition of ions which they need for specific purposes and have discovered new candidates with better performance in the organic-inorganic hybrid perovskite materials family. In this review, notable computational ways to assist the organic-inorganic hybrid perovskite materials research in recent years, including First Principals calculations or Density Functional Theory (DFT) calculations, and machine learning tools, have been summarized and discussed. The review shows various applications for First Principals and DFT calculations in this area, and also highlights the prominent potential for machine learning tools in finding new perovskite material candidates for novel solar cells.

Enhancing Photovoltaic Performance and Stability of Perovskite Solar Cells through Single-Source Evaporation and CsPbBr3 Quantum Dots Incorporation

This study investigates the potential of inorganic perovskite CsPbBr3 as a photovoltaic material, highlighting its superior stability compared to that of organic–inorganic hybrid perovskite materials. Conventional methods for preparing CsPbBr3 perovskite films, such as the two-step method and the dual-source thermal evaporation method, face challenges in obtaining high-purity films due to the decomposition of precursor films and the formation of multiple heterogeneous phases. To address this issue, we synthesized CsPbBr3 powder material using thermal evaporation deposition, which effectively suppressed decomposition and the formation of heterogeneous phases. Consequently, we achieved uniform and dense CsPbBr3 perovskite films. By incorporating energy-band engineering modification with CsPbBr3 quantum dots (QDs), the all-inorganic perovskite solar cells (PSCs) attained a power conversion efficiency (PCE) of 7.01% under standard solar illumination conditions. The device PCE remained at 93% of its initial efficiency under 30% relative humidity conditions for over 100 days, showcasing its durability. The developed method produced an average grain size of 800 nm, resulting in a smooth and uniform film surface, thereby demonstrating the method’s high repeatability. Additionally, the optimized PSCs exhibited a high open-circuit voltage (VOC) with the champion device reaching a VOC of 1.38 V and a PCE of 7.01%. This research presents a robust, efficient, and cost-effective approach for fabricating high-quality all-inorganic PSCs.

Highly Efficient and Stable Self-Powered Perovskite Photodiode by Cathode-Side Interfacial Passivation with Poly(Methyl Methacrylate).

For several years now, organic-inorganic hybrid perovskite materials have shown remarkable progress in the field of opto-electronic devices. Herein, we introduce a cathode-side passivation layer of poly(methyl methacrylate) (PMMA) for a highly efficient and stable self-powered CH3NH3PbI3 perovskite-based photodiode. For effective noise-current suppression, the PMMA passivation layer was employed between a light-absorbing layer of CH3NH3PbI3 (MAPbI3) perovskite and an electron transport layer of [6,6]-phenyl-C61-butyric acid methyl ester. Due to its passivation effect on defects in perovskite film, the PMMA passivation layer can effectively suppress interface recombination and reduce the leakage/noise current. Without external bias, the MAPbI3 photodiode with the PMMA layer demonstrated a significantly high specific detectivity value (~1.07 × 1012 Jones) compared to that of a conventional MAPbI3 photodiode without a PMMA layer. Along with the enhanced specific detectivity, a wide linear dynamic response (~127 dB) with rapid rise (~50 μs) and decay (~17 μs) response times was obtained. Furthermore, highly durable dynamic responses of the PMMA-passivated MAPbI3 photodiode were observed even after a long storage time of 500 h. The results achieved with the cathode-side PMMA-passivated perovskite photodiodes represent a new means by which to realize highly sensitive and stable self-powered photodiodes for use in developing novel opto-electronic devices.

Synthesis of Cs+-Tuned (PEA)2PbI4 Perovskite Thin Films by One-Step Spin Coating

As a candidate material for the next generation photovoltaic and light-emitting devices, organic-inorganic hybrid perovskite materials have attracted extensive attention. In this study, a (PEA)2PbI4 hybrid perovskite film was prepared by a one-step spin-coating method at room temperature. Based on the synthesis of (PEA)2PbI4, the inorganic Cs+ ions were doped in the film to investigate the influence of Cs+ doping on the structure and properties of two-dimensional (2D) perovskite film. The results show that both as-grown (PEA)2PbI4 film and Cs+-doped (PEA)2PbI4 film exhibit the instinct of the layered structure, though excess Cs+ ions doping would make the structure weakened. Through analyzing the optical properties, it is found that, besides the 2D (PEA)2PbI4 phase, a quasi-2D structure with two layers of [PbI6]4−-octahedron forms in Cs+-doped (PEA)2PbI4 perovskite films, which is ascribed to the phase rearrangement of the (PEA)2PbI4 crystal structure under the induction of Cs+ ions.