MAPbI3 Research Articles

Efficient and Scalable Radiative Cooling for Photovoltaics Using Solution‐Processable and Solar‐Transparent Mesoporous Nanoparticles

AbstractContinuous heat generation in perovskite solar cells (PSCs), caused by solar radiation, poses a significant challenge to their lifespan. Existing active cooling methods require extra energy input and might not be effective at high temperatures. Most reported passive radiative cooling materials either lack solar transparency or require complex fabrication processes. Here, mesoporous silica nanoparticles are designed, synthesized, and assembled into multilayered stacks with a graded refractive index (GRI) by spray coating them on top of PSCs made from methylammonium lead iodide (MAPbI3) over a large scale (15.6 × 15.6 cm2). This coating offers both high transparency in the visible wavelength and high emissivity in the mid‐infrared region, leading to an average temperature reduction of 6.65 ± 1.48 °C in GRI‐coated MAPbI3 PSCs under outdoor conditions compared to non‐coated references. After 50 d, the GRI‐coated PSCs maintain 80.9 ± 8.7% of their initial photoconversion efficiency, in contrast to 6.1 ± 5.9% for the noncoated ones. The calculated cooling power of the GRI‐coated PSCs is 28.9% higher than that of the reference cells.

Ultrasensitive dim-light neuromorphic vision sensing via momentum-conserved reconfigurable van der Waals heterostructure

Reconfigurable phototransistors featuring bipolar photoresponses are favorable for manipulating high-performance neuromorphic vision sensory. Here, we present a momentum-conserved reconfigurable phototransistor based on the van der Waals heterojunction between methylammonium lead iodide perovskite and two-dimensional Bi2O2Se semiconductor, which exhibits a synergistic interplay of interband hot-carrier transitions and reconfigurable heterointerface band alignments, eventually achieving the ultrahigh bipolar optoelectronic performances with the photoresponsivity of 6×107 AW−1, accompanied by the specific detectivity of 5.2×1011 Jones, and the dynamic range of 110 dB. Moreover, A 3×3 heterotransistor array is fabricated to perform in-sensor analog multiply-accumulate operations even under the challenging dim illumination of 0.1 μWcm−2 that comparable to natural moonlight. The reconfigurable heterotransistor array can be further adopted to enhance the traffic-light detection under dim-light conditions. Our advancement in momentum-conserved reconfigurable heterotransistor signifies a leap forward in real-time, energy-efficient, and low-light image processing for neuromorphic vision sensors.

Toward Water-Resistant, Tunable Perovskite Absorbers Using Peptide Hydrogel Additives.

In recent years, hydrogels have been demonstrated as simple and cheap additives to improve the optical properties and material stability of organometal halide perovskites (OHPs), with most research centered on the use of hydrophilic, petrochemical-derived polymers. Here, we investigate the role of a peptide hydrogel in passivating defect sites and improving the stability of methylammonium lead iodide (MAPI, CH3NH3PbI3) using closely controlled, in situ X-ray photoelectron spectroscopy (XPS) techniques under realistic pressures. Optical measurements reveal that a reduction in the density of defect sites is achieved by incorporating peptide into the precursor solution during the conventional one-step MAPI fabrication approach. Increasing the concentration of peptide is shown to reduce the MAPI crystallite size, attributed to a reduction in hydrogel pore size, and a concomitant increase in the optical bandgap is shown to be consistent with that expected due to quantum size effects. Encapsulation of MAPI crystallites is further evidenced by XPS quantification, which demonstrates that the surface stoichiometry differs little from the expected nominal values for a homogeneously mixed system. In situ XPS demonstrates that thermally induced degradation in a vacuum is reduced by the inclusion of peptide, and near-ambient pressure XPS (NAP-XPS) reveals that this enhancement is partially retained at 9 mbar water vapor pressure, with a reduced loss of methylammonium (MA+) from the surface following heating achieved using 3 wt % peptide loading. A maximum power conversion efficiency (PCE) of 16.6% was achieved with a peptide loading of 3 wt %, compared with 15.9% from a 0 wt % device, the former maintaining 81% of its best efficiency over 480 h storage at 35% relative humidity (RH), compared with 48% maintained by a 0 wt % device.

Halide Perovskite Thin Film Lasing Mode Control.

Metal halide perovskite semiconductors have emerged as highly efficient amplifying materials; to ensure practical applicability, it is important to have precise control over the spectral and polarization characteristics of lasing emission. In this study, we present effective strategies for manipulating single- and multimode lasing from surface-emitting and optically pumped perovskite distributed feedback lasers. We show that cladding structures can be made to modify the optical properties of guided transverse electric and magnetic modes within the gain medium. This leads to spectral tuning of multipeak lasing emission and the generation of linear polarization modes. Our results are supported with a comprehensive multilayer slab waveguide model and confirmed with two different perovskite materials: methylammonium lead iodide and cesium lead bromide.

Ionic liquid additive induced holistic trap-passivation for enhanced charge transport in lead-halide perovskite-based transistors

Incorporating ionic liquid additives into perovskite-based electronic devices has been considerably demonstrated to improve device performance and stability via synergistic passivation effects. However, the advantages and understanding of ionic additives in perovskite field-effect transistors (FETs) have been explored far less. Herein, holistic trap-passivation is reported in a poly(3-hexylthiophene)-functionalized electrolyte-gated perovskite FETs with a solid-state ionic liquid (ss-IL) additive. The optimized ss-IL-incorporated methylammonium lead iodide (MAPbI3/ss-IL) FETs exhibited remarkable hole mobility of over 30 cm2 V−1 s−1 at an operating voltage of –1.5 V, attributed to suppressed lead/iodine vacancies and related traps and exhibiting excellent operational stability under ambient conditions with recoverable complex hysteresis behavior. These results demonstrate the promising synergistic impacts of the proposed trap engineering and provide a fundamental understanding of charge transport physics in doped perovskite semiconductors, essential for advancing their application as transistor-based devices.

NiO/MWCNT incorporated methyl ammonium lead iodide for an efficient perovskite solar cells

The perovskite solar cells (PSCs) reveal the impressive performance due to the extraordinary characteristic features of perovskite material and its fabrication methods. The complex deposition process and hygroscopic nature of hole transport materials are biggest obstacles for attaining high power conversion efficiency (PCE) with long term stability in PSC. In this study, NiO/MWCNT nanocomposites have been synthesized by hydrothermal method and are incorporated in CH3NH3PbI3 to increase the performance of PSCs with stability. The incorporation has been carried out to improve the properties of CH3NH3PbI3 such as formation of large grain size/grain boundaries, reduce the defects that enhance the charge generation/collection and reduction in recombination. The fabricated PSCs with NiO/MWCNT revealed a PCE of 14.93 % with moderate hysteresis, which is significantly higher PCE than that of pristine PSC. The enhanced recombination resistance was observed by electrochemical impedance spectroscopy, which evinces the remarkable PCE of NiO/MWCNT incorporated PSC. The strong PL quenching and red shift of PL spectrum confirms the low recombination and larger grains in the NiO/MWCNT-CH3NH3PbI3 layer. Moreover, the NiO/MWCNT incorporated PSC retains 94 % of its initial PCE after 600 h of aging under atmospheric condition whereas the PCE of pristine PSC shows 87 % of its initial PCE value. The carbon back electrode also supports to lift up PCE and stability of PSCs.

Enhanced Structural, Optical, and photovoltaic properties of Sm-Doped MAPbI2Br perovskite solar cells

Samarium-enhanced methylammonium lead iodide bromide (Sm-MAPbI2Br) thin films were applied onto FTO-glass substrates. X-ray diffraction (XRD) analysis revealed an enlargement in grain size to 29.09 nm, a decrease in dislocation line density to 4.32 x 1015 m−2, an expansion in d-spacing to 5.18 Å, a reduction in lattice constant to 1.59 Å, and a diminished volume in the cubic crystal lattice of MAPbI2Br. The incorporation of Sm2+ ions resulted in a narrowed band gap energy (1.95 eV), an augmented refractive index (2.65), and a decreased extinction coefficient (2.24). The solar cell constructed with a 5 % Sm2+ doping level demonstrated an enhanced open-circuit voltage of 1.05 V, a notable increase in short-circuit current density to 9.87 mA/cm2, a fill factor of 0.80, and an elevated efficiency reaching 9.32 %. Comparative analyses suggest that the cell with 5 % Sm2+ doping experiences a lower rate of recombination compared to undoped MAPbI2Br-based cells. EIS is used to investigate enhanced charge transport in hybrid MAPbI2Br devices, emphasizing the impact of a Sm-doped thin layer on carrier dynamics. The robustness of the open-circuit voltage highlights the potential of layering MAPbI2Br in the development of highly efficient solar cells.

Nanometer-Resolved Mapping of Organic Cation Migration Behavior in Methylammonium Lead Halide Perovskites.

The performance and stability of organic metal halide perovskite (OMHP) optoelectronic devices have been associated with ion migration. Understanding of nanoscale resolved organic cation migration mechanism would facilitate structure engineering and commercialization of OMHP. Here, we report a three-dimensional approach for in situ nanoscale infrared imaging of organic ion migration behavior in OMHPs, enabling to distinguish migrations along grain boundary and in crystal lattice. Our results reveal that organic cation migration along OMHP film surface and grain boundaries (GBs) occurs at lower biases than in crystal lattice. We visualize the transition of organic cation migration channels from GBs to volume upon increasing electric field. The temporal resolved results demonstrate the fast MA+ migration kinetics at GBs, which is comparable to diffusivity of halide ions. Our findings help understand the role of organic cations in the performance of OMHP devices, and the proposed approach holds broad applicability for revealing migration mechanisms of organic ions in OMHPs based optoelectronic devices.

Numerical simulation of lead-free MASnI3 perovskite/silicon heterojunction for solar cells and photodetectors

Lead free n-type doped methyl ammonium tin iodide (MASnI3) perovskite/p-Silicon heterojunction (HJ) for solar cells and photodetectors are simulated using AFORS-HET automat simulation software. In the earlier work, lead based methyl ammonium lead iodide perovskite/silicon (n-MAPbI3/p-Si) heterojunction devices were studied. In view of the toxicity and environmental concerns related to lead, it is substituted with tin to make lead-free tin based perovskite to make n-MASnI3/p-Si HJ devices. Various parameters associated with the layers of MASnI3 perovskite and silicon wafer like, Band gap, thickness, doping concentration and texturing angle have been optimized. Various transparent conducting oxide (TCO) materials like indium tin oxide (ITO) and zinc oxide (ZnO) are used and its performance with ideal device is compared. Various metals are considered as front and back contact, to obtain best metals for each sides. This study investigates the potential of lead-free perovskite materials in solar cells, achieving a notable efficiency improvement compared to traditional lead-based counterparts. Our numerical simulations demonstrate that the optimized lead-free perovskite with structures, n-MASnI3/p-Si heterojunction can reach efficiencies of 27.2%. These findings suggest that lead-free perovskites could serve as a viable, environmentally friendly alternative in the photovoltaic industry.

Colloidal Quasi-2D Methylammonium Lead Bromide Perovskite Nanostructures with Tunable Shape and High Chemical Stability.

Control over the lateral dimensions of colloidal nanostructures is a complex task which requires a deep understanding of the formation mechanism and reactivity in the corresponding systems. As a result, it provides a well-founded insight to the physical and chemical properties of these materials. In this work, the preparation of quasi-2D methylammonium lead bromide nanostripes and discuss the influence of some specific parameters on the morphology and stability of this material is demonstrated. The variation in the amount of the main ligand dodecylamine gives a large range of structures beginning with 3D brick-like particles at low concentrations, nanostripes at elevated and ultimately nanosheets at large concentrations. The amount of the co-ligand trioctylphosphine can alter the width of the nanostripe shape to a certain degree. The thickness can be adjusted by the amount of the second precursor methylammonium bromide. Additionally, insights are given for the suggested formation mechanism of these anisotropic structures as well as for stability against moisture at ambient conditions in comparison with differently synthesized nanosheet samples.

Defect passivation of organometal halide perovskite solar cells using low-cost green crystalline nanocellulose

Perovskite solar cells (PSCs) have made significant progress in recent years. However, the presence of defects in the photoactive absorption layer has become a limiting factor in the efficiency of PSCs. In this research, methylammonium lead iodide perovskite films with improved quality and reduced defect density were obtained with the addition of crystalline nanocellulose (CNC) biopolymer. CNC produced from biomass contains many hydroxyl groups that were able to passivate the defects in perovskite, increase grain size, and reduce recombination. The PSC made with CNC modification achieved an efficiency of 9.22 %, higher than similar PSC without the addition of CNC that produced an efficiency of 7.28 %. This work highlights the passivating impact of low-cost green cellulose for enhancing the electrical performance of PSC.

Ultrafast Spin Relaxation of Charge Carriers in Strongly Quantum Confined Methylammonium Lead Bromide Perovskite Magic-Sized Clusters

Ultrafast Spin Relaxation of Charge Carriers in Strongly Quantum Confined Methylammonium Lead Bromide Perovskite Magic-Sized Clusters

Physical Properties of an Efficient MAPbBr3/GaAs Hybrid Heterostructure for Visible/Near-Infrared Detectors.

Semiconductor photodetectors can work only in specific material-dependent light wavelength ranges, connected with the bandgaps and absorption capabilities of the utilized semiconductors. This limitation has driven the development of hybrid devices that exceed the capabilities of individual materials. In this study, for the first time, a hybrid heterojunction photodetector based on methylammonium lead bromide (MAPbBr3) polycrystalline film deposited on gallium arsenide (GaAs) was presented, along with comprehensive morphological, structural, optical, and photoelectrical investigations. The MAPbBr3/GaAs heterojunction photodetector exhibited wide spectral responsivity, from 540 to 900 nm. The fabrication steps of the prototype device, including a new preparation recipe for the MAPbBr3 solution and spinning, will be disclosed and discussed. It will be shown that extending the soaking time and refining the precursor solution's stoichiometry may enhance surface coverage, adhesion to the GaAs, and film uniformity, as well as provide a new way to integrate MAPbBr3 on GaAs. Compared to the pristine MAPbBr3, the enhanced structural purity of the perovskite on GaAs was confirmed by X-ray Diffraction (XRD) upon optimization compared to the conventional glass substrate. Scanning Electron Microscopy (SEM) revealed the formation of microcube-like structures on the top of an otherwise continuous MAPbBr3 polycrystalline film, with increased grain size and reduced grain boundary effects pointed by Energy-Dispersive Spectroscopy (EDS) and cathodoluminescence (CL). Enhanced absorption was demonstrated in the visible range and broadened photoluminescence (PL) emission at room temperature, with traces of reduction in the orthorhombic tilting revealed by temperature-dependent PL. A reduced average carrier lifetime was reduced to 13.8 ns, revealed by time-resolved PL (TRPL). The dark current was typically around 8.8 × 10-8 A. Broad photoresponsivity between 540 and 875 nm reached a maximum of 3 mA/W and 16 mA/W, corresponding to a detectivity of 6 × 1010 and 1 × 1011 Jones at -1 V and 50 V, respectively. In case of on/off measurements, the rise and fall times were 0.40 s and 0.61 s or 0.62 s and 0.89 s for illumination, with 500 nm or 875 nm photons, respectively. A long-term stability test at room temperature in air confirmed the optical and structural stability of the proposed hybrid structure. This work provides insights into the physical mechanisms of new hybrid junctions for high-performance photodetectors.

Illuminating the Devolution of Perovskite Passivation Layers

Surface treatment of perovskite materials with their layered counterparts has become an ubiquitous strategy for maximizing device performance. While layered materials confer great benefits to the longevity and long‐term efficiency of the resulting device stack via passivation of defects and surface traps, numerous reports have previously demonstrated that these materials evolve under exposure to light and humidity, suggesting that they are not fully stable. Therefore, it is crucial to study the behavior of these materials in isolation and in conditions mimicking a device stack. Here, it is shown that perovskite capping layers templated by a range of cations on top of methylammonium lead iodide devolve in conditions commonly found during perovskite fabrication, such as exposure to light, solvent, and moisture. Photophysical, structural, and morphological studies are used to show that the degradation of these layered perovskites occurs via a self‐limiting, pinhole‐mediated mechanism. This results in the loss of whole perovskite sheets, from a few monolayers to tens of nanometers of material, until the system stabilizes again as demonstrated for exfoliated flakes of PEA2PbI4. This means that initially targeted structures may have devolved, with clear optimization implications for device fabrication.

Polycrystalline methylammonium-lead bromide perovskite films for photonic metasurfaces

Polycrystalline films of organo-inorganic perovskite semiconductors are promising as a foundation for creating functional optical metasurfaces. The requirements for film structural perfection, thickness uniformity, and defect-free characteristics are much more stringent compared to perovskite films for photovoltaics. This work presents the results of searching for optimal conditions for one-step synthesis of lead methylammonium bromide films using centrifugation, and describes the successful fabrication of subwavelength optical gratings from these films through focused ion beam processing. The measured spectra of light transmission through the gratings demonstrated their excellent optical quality and confirmed the possibility of creating semiconductor photon metasurfaces with submicrometer periodicity and high-Q dielectric resonances.

Potential Water Collection From Air by Chloride Perovskites.

Directly capturing water from the air has become a compelling strategy to secure water resources. Yet, challenges persist with sorption-based hygroscopic materials, such as inadequate water adsorption efficiency, material degradation post-adsorption, and the need for energy input during water collection. This study introduces an alternative category of sorbent materials potentially for atmospheric water harvesting-metal chloride perovskites-that exhibit spontaneous water vapor adsorption and liquid water collection. This water uptake capability stems from the uncoordinated polar ions that form hydrogen bonds with water molecules, while the cubic lattice imparts a solid framework ensuring structural stability and inhibiting hydrolysis. The methylammonium lead chloride perovskite pellets exhibit efficient water collection performance, with a record absorption rate of 0.841 L m-2 h-1 and a total water collection of 3.675 L m-2 within a 7-h cycle. This initiative attempts to provide a new material class candidate for the potential application of passive atmospheric water harvesting.

Influence of post-thermal treatment on characteristics of polycrystalline hybrid halide perovskite nanoparticles thin film

A three-dimensional organic–inorganic hybrid halide perovskite (CH3NH3PbI2Br) nanoparticle film was synthesized using solution process in one step. Precursors’ stoichiometry was used to prepare methylammonium bromide and lead (II) bromide in dimethyl formamide. The synthesized CH3NH3PbI2Br solution was spin coated on cleaned ITO prepatterned glass substrate at 2000 rpm. In addition, the influence of post-thermal treatment on the deposited nanoparticles films was evaluated by studying the structural, optical and morphological properties using X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) spectrometry, UV–visible spectrophotometry, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The average crystallite sizes were calculated to be ~ 8.0, ~ 9.4, ~ 11.3 and ~ 13.1 nm of as-prepared and annealed films at 400, 500 and 600 °C, respectively. Besides, the bandgaps of 2.22 eV, 1.96 eV, 1.89 eV and 1.63 eV were extrapolated for as-prepared and annealed films at 400 °C, 500 °C and 600 °C, respectively. From J–V curves, the Jsc values of 9.4, 10.6, 11.7 and 12.8 mAcm−2, FF values of 56.99%, 57.25%, 58.94% and 59.26% and PCE values of 2.99%, 3.49%, 3.96% and 4.39% were calculated for as-prepared and annealed CH3NH3PbI2Br films at 400 °C, 500 °C and 600 °C, respectively. The percentage enhancement values of 14.32%, 24.49% and 31.89% compared to as-prepared CH3NH3PbI2Br film. Hence, post-thermal treatment of organic–inorganic halide perovskite material improved its photoconversion efficiency without sacrificing its dimensionality.

Many-Body MYP2 Force-Field: Toward the Crystal Growth Modeling of Hybrid Perovskites.

Hybrid perovskites are well-known for their optoelectronic and photovoltaic properties. Molecular dynamics simulations allow the study of these soft and ionic crystals by including dynamical effects (e.g., molecular rotations, octahedra tilting, ionic diffusion and hysteresis), yet the high computational cost restricts the use of accurate ab initio forces for bulk or small atomic systems. Hence, great interest exists in the development of classical force-fields for hybrid perovskites of low and linear scaling computational cost, via both empirical methods and machine-learning. This work aims at extending the transferability of our MYP0 model, which has been successfully tailored to methylammonium lead iodide (MAPI) and applied to the study of molecular rotations, vibrations, diffusion of defects, and many other properties. The extended model, named MYP2, improves the description of inorganic or hybrid fragments and the processes of crystal formation while preserving a good description of bulk properties. More importantly, it allows for the direct simulation of the crystal growth of cubic MAPI from deposition of PbI and MAI precursors on the surfaces. Our findings pave the way toward classical force-fields able to model the microstructure evolution of hybrid perovskites and the crystalline synthesis from deposition in vacuo.

Optimizing Methylammonium Lead Iodide Perovskite Synthesis for Solar Cells via Two-step Spin Coating with Mixed Solvents

Optimizing Methylammonium Lead Iodide Perovskite Synthesis for Solar Cells via Two-step Spin Coating with Mixed Solvents

(Invited) Progresses on Plasma Processing of Halide Perovskite Materials for Photovoltaic Applications

Metal halide perovskite (MHPs) solar cells represent a promising newcomer in the front of emerging photovoltaic technologies to address the dramatic energy crisis and climate change that we are facing. The exceptional properties of MHPs derive from their hybrid organic-inorganic nature, which allows also for low-cost and straightforward processing. Solar cells containing MHPs as absorbing layer have already achieved a power conversion efficiency of about 25,7 %, close to the efficiency of silicon-based devices. Nevertheless, a major limitation, still preventing the uptake of the technology, is related to the reduced stability of these materials when exposed to operative conditions, namely temperature, light, and moisture. Herein, an effective defect passivation of MHP surfaces is a key strategy to tackle both the stability and the enhancement of solar cell performances. Although many solution-based approaches 1 have been tested, we propose here an innovative use of plasma, as a solvent-free, scalable, and non-invasive promising strategy to boost MHP solar cells performances 2. As starting point we exposed the surface of Methylammonium Lead Iodide perovskite thin films to different plasma conditions implying the variation of power, gas, and treatment time, both for low-pressure (LP) and atmospheric pressure plasmas (APPs). The impact of Ar, , and LPPs on MAPbI3 optochemical properties and morphology was correlated to the performance of the photovoltaic devices and rationalized by density functional theory calculations3. Herein an interesting improvement in photoluminescence was observed for the Ar and treated films, while an improvement in PCE was observed only for the Ar treated device. This result was ascribed to the efficient removal of the superficial organic component, revealed through X-ray photoelectron spectroscopy (XPS), following suitable surface passivation by the electron transporting layer deposition. Following these results, we tested APP treatments, finding a milder morphological modification than LPP treatments but withstanding good surface passivation, as confirmed through the improved photoluminescence intensity, while the effect in terms of photovoltaic devices is still under investigations. Moving from these encouraging results, we applied plasma surface treatments to tin-based perovskite, finding a very interesting beneficial effect when reductive plasma conditions (forming gas) were used on FaSnI3 thin film.4 The collection of these results already show the great versatility and potential of plasma-based techniques for the intelligent modification of metal halide perovskite for solar energy conversion.