Organic Hybrid Perovskite Research Articles

Encapsulating Halide Perovskite Quantum Dots in Metal–Organic Frameworks for Efficient Photocatalytic CO2 Reduction

Halide perovskite has shown great potential in photocatalysis owing to its diversity, suitable energy band alignment, rapid charge transfer, and excellent optical properties. However, poor stability, especially under humid conditions, hinders their practical application in photocatalysis. In this work, we report the encapsulation of inorganic–organic hybrid perovskite QDs into MIL-101(Cr) through an in situ growth strategy to prepare a series of MAPbBr3@MIL-101(Cr) (MA = CH3NH3+) composites. The perovskite precursors, i.e., MABr and PbBr2, were successively introduced into the pores of MOF, where the perovskite quantum dots were self-assembled in the confined environment. In photocatalytic CO2 reduction, 11%MAPbBr3@MIL-101(Cr) composite displayed the best performance among the composites with a total CO and CH4 yield of 875 μmol g−1 in 9 h, which was 8 times higher than that of the pure MAPbBr3. Such high gas production efficiency could be maintained for 78 h at least without structural and morphologic decomposition. The remarkable stability and catalytic activity of composites are mainly due to the synergistic effect and improved electron transfer between MAPbBr3 and MIL-101(Cr). Moreover, these composites revealed a novel mechanism, showing switched CH4 selectivity with the controlling of the perovskite location and contents. Those with perovskites encapsulated in the mesopores of MIL-101(Cr) were more preferential for CO production, while those with perovskites encapsulated in both meso- and micropores could produce CH4 dominantly.

The influence of perovskite crystal structure on its stability

The relationship between structure and stability of organic and inorganic hybrid perovskite was analyzed by a model interpretability technique. We found that perovskites containing iodine were the most stable, followed by bromine and finally chlorine.

Generation of Long-Lived Excitons in Room-Temperature Phosphorescence 2D Organic and Inorganic Hybrid Perovskites for Ultrafast and Low Power-Consumption Nonvolatile Photomemory.

Room-temperature phosphorescence (RTP) two-dimensional (2D) organic-inorganic hybrid perovskites (OIHPs) that possess superior stability and efficient triplet energy transfer between inorganic parts and organic cations have been seen as promising materials in optoelectronic devices. However, the development of RTP 2D OIHP-based photomemory has not been explored yet. In this work, the spatially addressable RTP 2D OIHPs-based nonvolatile flash photomemory is first investigated to explore the function of triplet excitons in elevating the performance of photomemory. Thanks to the triplet excitons generated in RTP 2D OIHP, extremely low photo-programming time of 0.7ms, multilevel behavior of minimum 7 bits (128 levels), remarkable photoresponsivity of 19.10 AW-1 and significantly low power consumption of 6.79 × 10-8 J per bit can be achieved. The current study provides a new prospective in understanding triplet excitons function in nonvolatile photomemory.

A Review of Perovskite Nanocrystal Applications in Luminescent Solar Concentrators

AbstractLuminescent solar concentrators (LSCs) are capable of absorbing solar light over a large area, which subsequently converts light into luminescence at a red‐shifted wavelength and then redirects it to a smaller target to increase the per‐unit yield of photovoltaic devices. Among various LSC materials, perovskite nanocrystals (NCs) have attracted great attention due to their adjustable band gap, multi‐exciton effect, and good stability. In this review, a brief introduction of LSCs, including their advances and principles, is given, followed by a summary of perovskite‐NCs‐based LSCs. The selected examples for component optimization of inorganic perovskite NCs are outlined after an introduction to the structure and properties of perovskite NCs. The absorption and/or emission peaks of all‐inorganic and inorganic–organic hybrid perovskite NCs can be efficiently regulated, which not only increases the Stokes shift but also improves the stability. Excellent performance and operability show a bright application prospect of perovskite NCs in the field of LSC applications.

Theory of Nonlinear Excitonic Response of Hybrid Organic Perovskites in the Regime of Strong Light-Matter Coupling

We present a quantitative study of the nonlinear optical response of layered perovskites placed inside planar photonic microcavities in the regime of strong light matter coupling, when excitonic and photonic modes hybridize and give rise to cavity polaritons. Two sources of nonlinearity are specified, the saturation of the excitonic transition with increase of the optical pump and Coulomb interaction between the excitons. It is demonstrated, that peculiar form of the interaction potential, specific to multilayer structure of organic perovskites, is responsible for substantial increase of the exciton binding energy and Rabi splitting with respect to conventional semiconductor systems. This results in dominant contribution of the Rabi splitting quench effect in the nonlinear optical response. Moreover, due to the tightly bound character of excitons, the density of Mott transition is essentially higher, allowing to reach extremely large polariton blueshifts of about 50 meV, which is order of magnitude higher than in conventional semiconductors.

Confinement of Luminescent Guests in Metal-Organic Frameworks: Understanding Pathways from Synthesis and Multimodal Characterization to Potential Applications of LG@MOF Systems.

This review gives an authoritative, critical, and accessible overview of an emergent class of fluorescent materials termed “LG@MOF”, engineered from the nanoscale confinement of luminescent guests (LG) in a metal–organic framework (MOF) host, realizing a myriad of unconventional materials with fascinating photophysical and photochemical properties. We begin by summarizing the synthetic methodologies and design guidelines for representative LG@MOF systems, where the major types of fluorescent guest encompass organic dyes, metal ions, metal complexes, metal nanoclusters, quantum dots, and hybrid perovskites. Subsequently, we discuss the methods for characterizing the resultant guest–host structures, guest loading, photophysical properties, and review local-scale techniques recently employed to elucidate guest positions. A special emphasis is paid to the pros and cons of the various methods in the context of LG@MOF. In the following section, we provide a brief tutorial on the basic guest–host phenomena, focusing on the excited state events and nanoscale confinement effects underpinning the exceptional behavior of LG@MOF systems. The review finally culminates in the most striking applications of LG@MOF materials, particularly the “turn-on” type fluorochromic chemo- and mechano-sensors, noninvasive thermometry and optical pH sensors, electroluminescence, and innovative security devices. This review offers a comprehensive coverage of general interest to the multidisciplinary materials community to stimulate frontier research in the vibrant sector of light-emitting MOF composite systems.

A descriptor for the structural stability of organic-inorganic hybrid perovskites based on binding mechanism in electronic structure.

The poor stability of organic-inorganic hybrid perovskites hinders its commercial application, which motivates a need for greater theoretical insight into its binding mechanism. To date, the binding mode of organic cation and anion inside organic-inorganic hybrid perovskites is still unclear and even contradictory. Therefore, in this work based on density functional theory (DFT), the binding mechanism between organic cation and anion was systematically investigated through electronic structure analysis including an examination of the electronic localization function (ELF), electron density difference (EDD), reduced density gradient (RDG), and energy decomposition analysis (EDA). The binding strength is mainly determined by Coulomb effect and orbital polarization. Based on the above analysis, a novel 2D linear regression descriptor that Eb = - 9.75Q2/R0 + 0.00053V∙EHL - 6.11 with coefficient of determination R2 = 0.88 was proposed to evaluate the binding strength (the units for Q, R0, V, and EHL are |e|, Å, bohr3, and eV, respectively), revealing that larger Coulomb effect (Q2/R0), smaller volume of perovskite (V), and narrower energy difference (EHL) between the lowest unoccupied molecular orbital (LUMO) of organic cation and the highest occupied molecular orbital (HOMO) of anion correspond to the stronger binding strength, which guides the design of highly stable organic-inorganic hybrid perovskites.

Phototransistors Based on Organic Small Molecules–Ruddlesden‐Popper Layered Perovskite Single Crystal Heterojunctions

AbstractIn photodetectors based on heterojunctions of organic semiconductor and hybrid perovskite, the strong light absorbing ability of perovskite and the gate‐tunability of organic semiconductor can be preferably incorporated. However, the charge current transfer at the interface, and the double channel transportation in the heterojunctions are not fully understood. The authors successfully transfer the mechanically exfoliated Ruddlesden–Popper (RP) layered perovskite single crystal to the thermal evaporated organic small molecule semiconductor forming a heterojunction. Based on the heterojunction, two configurations of light detecting devices are prepared in which the perovskite layer acts as either a conducting channel and light absorbing layer or light absorbing layer only. The light detecting performance of such devices is systematically investigated. The charge transfer from the perovskite single crystal to the organic semiconductor layer is observed by Kelvin Probe Force Microscope characterization. They also find that the n values of the RP layered perovskite can significantly influence the property of the heterojunction and charge transfer process. For single channel devices a responsivity of 5.87 × 102 A W−1 and a detectivity of 5.13 × 1012 Jones is realized.

Numerical investigation of solar cells based on hybrid organic cation perovskite with inorganic HTL via SCAPS-1D

Among the major problems hindering the performance and commercialisation of conventional MAPbI3 solar cells are thermal instability, degradation, defects and the high cost of Spiro-OMeTAD HTL. However, the hybrid or mixed organic cation perovskite (MA1-xFAxPbI3) has good crystallinity which can reduce defects and increase the charge carrier lifetime. The aim of this work is to find, by numerical simulation using SCAPS-1D software, a better substitute for organic Spiro-OMeTAD HTL in order to solve the problems caused by it. First, we validated our solar cell structures by a comparative study of the J-V characteristics of the experiment and the simulation. Secondly, we conducted a numerical simulation study of a number of inorganic HTLs (NiO, CuI, CuSCN, MoO3, and Cu2O) that replace Spiro-OMeTAD in the hybrid organic cation perovskite cell structure. Based on the study of the performance and stability of these different HTLs, we obtain Cu2O HTL as the best candidate to substitute the organic Spiro-OMeTAD HTL. The MA1-xFAxPbI3-based solar cell with Cu2O as inorganic HTL shows a very good stability (TC = -0.0014%/°C) and better performance with an efficiency of 26.67%. This work contributes to a better knowledge on the numerical optimization of perovskite-based solar cells.

Low-Temperature Deposited Highly Flexible In–Zn–V–O Transparent Conductive Electrode for Perovskite Solar Cells

Inorganic–organic hybrid perovskite solar cells (PSCs) typically embrace Sn-doped In2O3 (ITO) and F-doped SnO2 (FTO) as transparent electrodes, which are rigid and brittle, retarding the commercialization of flexible PSCs (FPSCs). Here, we fabricated flexible amorphous transparent V-doped In–Zn–O (IZVO) thin films with varied concentrations of V atoms at room temperature. The impacts of V concentration on the chemical, electrical, and optical properties of IZVO thin films were thoroughly investigated. The incorporation of V into IZO was demonstrated to suppress the formation of oxygen vacancies and thus reduce the carrier concentration in IZO. The IZVO thin film affords the best electrode performance with an optimum V concentration of 0.46 atom %. In contrast to the conventional ITO transparent electrodes that require a high processing temperature, the amorphous transparent IZVO electrode deposited at a low temperature without any heating and postannealing process showed a low sheet resistance (∼22.6 Ω/□), high conductivity (∼2210 S/cm), high optical transmittance (∼88.8%), and in particular, excellent mechanical flexibility and fatigue robustness. Therefore, the amorphous transparent IZVO electrode-based perovskite solar cells (PSCs) showed superior performance (14.57%) compared to the amorphous ITO electrode-based PSCs (11.96%), due to the significantly improved short-circuit current density (JSC), open-circuit voltage (VOC), and fill factor (FF). Moreover, the IZVO electrode-based FPSC device retained 77% of its initial power conversion efficiency (PCE) after 100 bending cycles, while the PCE of the amorphous ITO electrode-based FPSC dropped by 80% after only 30 bending cycles. Combining the excellent mechanical flexibility and fatigue robustness, the flexible amorphous IZVO electrode shows great potential for highly efficient flexible photovoltaic applications.

Modeling and characteristics of a nanostructured NiO/GeSe core–shell perovskite solar cell

Inorganic–organic hybrid perovskite solar cells (PSCs) have recently seen considerable progress, and this has encouraged researchers to evolve and test numerous different and potentially improved device architectures. As a result, in this paper, a theoretical design for improving light absorption to obtain maximum photocurrent using NiO/GeSe core–shell nanostructures is introduced. The effects of using nanostructure arrays, based on the light trapping technique, on the light absorption, generation of carriers, absorption field profiles, and finally the photocurrent density of PSCs, have been investigated through a three-dimensional finite-difference time-domain approach. By selecting NiO and GeSe as the core and the shell materials, the absorption of the active layer has been increased, relative to the use of a conventional planar structure. This core–shell nanostructure leads to a reduction in the carrier recombination within the PSC proposed design. The results obtained from our simulation show that the device performance is highly dependent on the height and materials used in the core–shell. Significantly, an optimal height of 160 nm was obtained for core–shell in a PSC design with a J ph value of 27.23 m A / c m 2 .

Flexible light-responsive self-healing polymeric composite film based on two-dimensional MoS2 - organic halide perovskite longitudinal heterostructure

Organic hybrid perovskite (OHP) is one of the most attractive optical absorbable and reactive materials. However, excellent light-responsive self-healing polymeric composite film based on OHP is difficult to obtain. Here, four two-dimensional (2D) OHP with different typical sizes and morphologies were prepared by regulating with four different typical diamines, and the novel scale-like plate-stack 2D MoS2-OHP longitudinal heterostructure was fabricated. Then, a valid structure strategy, utilizing 2D MoS2-OHP as the light-responsive material and self-healing polyurethane (PU) as polymer matrix, is firstly developed to realize high performance light response. Among these light responsive self-healing polymer materials, the MoS2-OHP-3/PU composite film exhibited excellent figures of merit, including high light stimulation response (ΔR value was 70.0589 MΩ), strong tensile strength value (8.06 ± 0.05 MPa), high maximum elongation (467 ± 13.82%), high self-healing efficiency (80% for mechanical properties, 95% for light-response) and ultra-high humidity stability (86% for light response, 81.89% mechanical properties). This work provided a novel method and a feasible substrate for the development of self-healing, flexible and scalable intelligent response soft materials.

Thermochromic Smart Windows: Organic Hybrid Perovskite (MAPbI3−xClx) for Thermochromic Smart Window with Strong Optical Regulation Ability, Low Transition Temperature, and Narrow Hysteresis Width (Adv. Funct. Mater. 26/2021)

Thermochromic Smart Windows: Organic Hybrid Perovskite (MAPbI₃₋<i>_x</i>Cl<i>_x</i>) for Thermochromic Smart Window with Strong Optical Regulation Ability, Low Transition Temperature, and Narrow Hysteresis Width (Adv. Funct. Mater. 26/2021)

Lead-free tin perovskite solar cells

Summary The development of efficient and stable lead-free perovskite solar cells (PSCs) is crucial for addressing the concern of environmental pollution from the toxic element lead. In recent years, tin PSCs have emerged as a promising candidate for high-performance, eco-friendly photovoltaic technology with a high certified power conversion efficiency (PCE) of more than 11%, indicating a great potential for future applications. Here, we review the recent efficiency progress of tin PSCs based on the equivalent circuit model of solar cells. We then discuss approaches toward efficiency improvement from the device viewpoint, such as optimizing the band gap, increasing the light-harvesting efficiency and carrier diffusion length, surface passivation, and regulating the interface energy-level alignment. Finally, we point out the possibility of reaching 20% PCE for tin PSCs and issues regarding enlarging the cell size and realizing scalable production in the future. We expect that these perspectives will be helpful for accelerating the commercialization of tin PSCs.

A common optical approach to thickness optimization in polymer and perovskite solar cells

The structure of experimentally designed solar cells was optimized in terms of the photoactive layer thickness for both organic bulk heterojunction and hybrid perovskite solar cells. The photoactive layer thickness had a totally different behavior on the performance of the organic and hybrid solar cells. Analysis of the optical parameters using transfer matrix modeling within the Maxwell–Garnett effective refractive index model shows that light absorbance and exciton generation rate in the photoactive layer can be used to optimize the thickness range of the photoactive layer. Complete agreement between experimental and simulated data for solar cells with photoactive materials that have very different natures proves the validity of the proposed modeling method. The proposed simple method which is not time-consuming to implement permits to obtain a preliminary assessment of the reasonable range of layer thickness that will be needed for designing experimental samples.

Device simulation of all-perovskite four-terminal tandem solar cells: towards 33% efficiency

Inorganic–organic hybrid perovskites offer wide optical absorption, long charge carrier diffusion length, and high optical-to-electrical conversion, enabling more than 25% efficiency of single-junction perovskite solar cells. All-perovskite four-terminal (4T) tandem solar cells have gained great attention because of solution-processability and potentially high efficiency without a need for current-matching between subcells. To make the best use of a tandem architecture, the subcell bandgaps and thicknesses must be optimized. This study presents a drift-diffusion simulation model to find optimum device parameters for a 4T tandem cell exceeding 33% of efficiency. Optimized subcell bandgaps and thicknesses, contact workfunctions, charge transport layer doping and perovskite surface modification are investigated for all-perovskite 4T tandem solar cells. Also, using real material and device parameters, the impact of bulk and interface traps is investigated. It is observed that, despite high recombination losses, the 4T device can achieve very high efficiencies for a broad range of bandgap combinations. We obtained the best efficiency for top and bottom cell bandgaps close to 1.55 eV and 0.9 eV, respectively. The optimum thickness of the top and bottom cells are found to be about 250 nm and 450 nm, respectively. Furthermore, we investigated that doping in the hole transport layers in both the subcells can significantly improve tandem cell efficiency. The present study will provide the experimentalists an optimum device with optimized bandgaps, thicknesses, contact workfunctions, perovskite surface modification and doping in subcells, enabling high-efficiency all-perovskite 4T tandem solar cells.

Lead Free Two-Dimensional Mixed Tin and Germanium Halide Perovskites for Photovoltaic Applications

Recently, inorganic–organic hybrid perovskites have gained immense attention in view of its outstanding performance in solar cell devices. Due to the toxicity of lead, lead-free perovskites are hig...

A mechanistic investigation of moisture-induced degradation of methylammonium lead iodide

We performed in situ x-ray diffraction (XRD) experiments on an inorganic–organic hybrid perovskite, CH3NH3PbI3 (MAPbI3), during its interaction with moisture to understand the degradation mechanism. Although the degradation of inorganic–organic hybrid perovskite is an important factor hampering their development as solar cell materials, understanding of the degradation process is currently limited. The moisture-induced degradation mechanism was revealed by the temperature dependence of the in situ XRD pattern sequences and first-principles calculations based on the nudged elastic band method. The combination of experimental and computational data suggests that the MAPbI3 crystal spontaneously changes into the MAPbI3 mono-hydrate crystal once water molecules activated with an energy of more than ∼0.6 eV penetrate the (100) outer surface of the MAPbI3 lattice. These findings have important implications for the development of more robust inorganic–organic hybrid perovskites as light absorbing layers in solar cells and other applications.

Effect of wettability of substrate on metal halide perovskite growth

In the last decade, inorganic–organic hybrid perovskites have demonstrated a dramatic increase in photoconversion efficiency by engineering the perovskite composition, as well as adjusting the properties of the charge transporting materials. The nucleation and growth of the perovskite layer are governed by the surface properties of the substrate and depend on its wetting properties defined by the roughness and the species adsorbed. Fixing all fabrication conditions of a PSC but only changing the wettability of the substrate is practically difficult because varying the surface hydrophilicity can contribute side effects such as chemical identity change or adsorption of new species on the surface. Herein, we studied a double-layered TiO2/SnO2 ETL for perovskite deposition and we changed the hydrophilicity of the samples using hydrophobic recovery after UV exposure. Thus, the effect of wettability of the substrate on nucleation and growth of the perovskite layer was elucidated under minimized interference. It was found that the influence of the wetting properties of the substrate on the growth of perovskite can be exaggerated in the literature since the increase in the grain size of the perovskite layer is just 14% bigger if the water contact angle of the substrate increases from 3° to 72°.

Recent Progress on the Stability of Perovskite Solar Cells in a Humid Environment

In recent years, photovoltaic devices based on inorganic–organic hybrid perovskite materials have become one of the most promising research subjects in the field of energy conversion. CH3NH3PbI3 st...