Metal Halide Perovskite Films Research Articles

Efficient perovskite light-emitting diodes on a flexible substrate.

The surface properties of target substrates are crucial for the in situ crystallization and growth of metal halide perovskite films fabricated by the anti-solvent method. In this work, a high-quality quasi-2D perovskite film with various-n phases is fabricated on the commonly used poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) by introducing a branched polyethylenimine (PEI) modifying layer. PEI suppresses the influence of acidic surface of the PEDOT:PSS and regulates the components of the perovskite film, increasing the proportion of large-n phases. Additionally, PEI reduces the formation of defects in perovskite films, leading to higher photoluminescence quantum efficiency and longer photoluminescence lifetime. Based on this high-quality perovskite film, a flexible light-emitting diode with an ultimate current efficiency of 63.2 cd/A is achieved, nearly twofold higher than that of the device (35.1 cd/A) without a PEI modifying layer.

Enhancing the Performance of Perovskite Light-Emitting Diodes via Synergistic Effect of Defect Passivation and Dielectric Screening

HighlightsSynergistic passivation mechanism of the dual functional compound of potassium bromide for metal halide perovskite films, that is through chemical bonding and physical screening towards the various types of defects.Metal-ion additives can simultaneously passivate the defects of halide vacancies with bromine anions and dangling bond defects with metal cations.Achieve the maximum external quantum efficiency of ~21% and maximum luminance of ~60,000 cd m−2.

Residual Stress Mitigation in Perovskite Solar Cells via Butterfly-Inspired Hierarchical PbI2 Scaffold.

Residual stress in metal halide perovskite films intimately affects the photovoltaic figure of merit and longevity of perovskite solar cells. A delicate management of the crystallization kinetics is critical to the preparation of high-quality perovskite films. Only very limited methods, however, are available to regulate the residual stress of a perovskite film in a controllable manner, particularly for a perovskite film fabricated by a two-step method. Here, we demonstrate the construction of a hierarchical PbI2 scaffold inspired by Archaeoprepona demophon butterfly by combining an interlayer guided growth of porous structure and nanoimprinting. The hierarchically structured PbI2 that emulates the physical structure of the butterfly wing scale permits unimpeded permeation of organic amine salts and sufficient space for volume expansion during the crystallization process, accompanied by preferential perovskite growth of a defectless (001) crystal plane. The optimized perovskite film outperforms the control with reduced residual stress and defect density. Consequently, perovskite solar cells with a respectable power conversion efficiency reaching 23.4% (certified 23%) and an impressive open-circuit voltage of 1.184 V can be achieved. The target device can maintain 80% of initial efficiency after maximum power point tracking under illumination for 700 h. This work expands the range of engineering toward PbI2 by exploring a simultaneously tailored morphology and crystallinity and highlights the significance of a hierarchical PbI2 scaffold as an alternative choice to mitigate residual stress in a two-step processed perovskite active layer and boost the longevity of perovskite solar cells.

Mixed-cation, mixed-halide perovskite ToF-SIMS spectra

We report positive and negative ion time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra of metal-halide perovskite (MHP) films used for photovoltaic applications. This ToF-SIMS spectral library is of importance because it identifies the major peaks in most MHP films from organic [formamidinium (FA+)] and inorganic (Cs+) cations and anions (I− and Br−).

Plasma‐Based Technologies for Halide Perovskite Photovoltaics

Plasma‐based technologies are at the frontier of material processing for several applications, from packaging to agronomy to photovoltaics. These processes allow for a fine‐tuning of material properties by engineering deposition, interaction with the substrate, and final surface characteristics at the atomistic level. As metal halide perovskite (MHP) solar cells enter the path toward commercialization, plasma processing can be seen as a powerful material manipulation tool already settled within industrially relevant procedures. In this perspective, the impact that these methods can have on different aspects of perovskite solar cells technology is envisioned, focusing on the direct interaction between plasma and MHPs. The use of plasma processes is foreseen for the deposition or crystallization of MHPs films, for treating their surface, as well as for the creation of suitable coatings either on top of perovskite layer and/or as encapsulants of the whole solar converting devices.

Molecular design of defect passivators for thermally stable metal-halide perovskite films

Molecular design of defect passivators for thermally stable metal-halide perovskite films

Resolving electron and hole transport properties in semiconductor materials by constant light-induced magneto transport

The knowledge of minority and majority charge carrier properties enables controlling the performance of solar cells, transistors, detectors, sensors, and LEDs. Here, we developed the constant light induced magneto transport method which resolves electron and hole mobility, lifetime, diffusion coefficient and length, and quasi-Fermi level splitting. We demonstrate the implication of the constant light induced magneto transport for silicon and metal halide perovskite films. We resolve the transport properties of electrons and holes predicting the material’s effectiveness for solar cell application without making the full device. The accessibility of fourteen material parameters paves the way for in-depth exploration of causal mechanisms limiting the efficiency and functionality of material structures. To demonstrate broad applicability, we further characterized twelve materials with drift mobilities spanning from 10–3 to 103 cm2V–1s–1 and lifetimes varying between 10–9 and 10–3 seconds. The universality of our method its potential to advance optoelectronic devices in various technological fields.

Waterproof and Flexible Perovskite Photodetector Enabled By P-type Organic Molecular Rubrene with High Moisture and Mechanical Stability.

Metal halide perovskite films have gained significant attention because of their remarkable optoelectronic performances. However, their poor stability upon the severe environment appears to be one of the main facets that impedes their further commercial applications. Herein, a method to improve the stability of flexible photodetectors under water and humidity environment without encapsulation is reported. The devices are fabricated using the physical vapor deposition method (Pulse Laser Deposition & Thermal Evaporation) under high-vacuum conditions. An amorphous organic Rubrene film with low molecular polarity and high elastic modulus serves as both a protective layer and hole transport layer. After immersed in water for 6000min, the photoluminescence intensity attenuation of films only decreased by a maximum of 10%. The demonstrator device, based on Rubrene/CsPbBr3/ZnO heterojunction confirms that the strategy not only enhances device moisture and mechanical stability but also achieves high sensitivity in optoelectronic detection. In self-powered mode, it has a fast response time of 79.4 µs /207.6 µs and a responsivity 124mAW-1. Additionally, the absence of encapsulation simplifies the fabrication of complex electrodes, making it suitable for various applications. This study highlights the potential use of amorphous organic films in improving the stability of perovskite-based flexible devices.

Chemical polishing and sub-surface passivation of perovskite film towards high efficiency solar cells

Eliminating surface defects and impurities on metal halide perovskite (MHP) films through chemical reactions represents a novel strategy to improve the performance of perovskite solar cells (PSCs), which can be referred to as “chemical polishing”. This approach is anticipated to be more facile, precise, and distinct from the extensively documented surface passivation methods in terms of its underlying mechanism. However, to date, the underlying selective chemical reaction mechanism still requires in-depth study. In this context, we present a novel two-step chemical polishing method that eliminates surface impurities while simultaneously passivating the sub-surface. The core principle of this method involves two primary steps: (1) the creation of two-dimensional (2D) perovskite via selective reactions between polishing agents (n-octylammonium bromide, OABr) and undesired metastable amorphous species, as well as residual PbI2 nanocrystals present on the surface of MHP films. (2) Subsequently, the 2D perovskite and excess polishing agents are efficiently eliminated using a mixed solvent. Following the polishing process, the sub-surface, which is passivated by residual OABr, contains fewer defects and can establish improved electrical contact with the hole transport layer (HTL). As a result, the power conversion efficiency (PCE) of PSCs is enhanced from 21.7% to 23.6%. Moreover, the PSCs processed with chemical polishing exhibit enhanced long-term operational stability, with a capability to retain 80.2% of their original PCE value after 1500 h of illumination.

Moisture-Resilient Perovskite Solar Cells for Enhanced Stability.

With the rapid rise in device performance of perovskite solar cells (PSCs), overcoming instabilities under outdoor operating conditions has become the most crucial obstacle toward their commercialization. Among stressors such as light, heat, voltage bias, and moisture, the latter is arguably the most critical, as it can decompose metal-halide perovskite (MHP) photoactive absorbers instantly through its hygroscopic components (organic cations and metal halides). In addition, most charge transport layers (CTLs) commonly employed in PSCs also degrade in the presence of water. Furthermore, photovoltaic module fabrication encompasses several steps, such as laser processing, subcell interconnection, and encapsulation, during which the device layers are exposed to the ambient atmosphere. Therefore, as a first step toward long-term stable perovskite photovoltaics, it is vital to engineer device materials toward maximizing moisture resilience, which can be accomplished by passivating the bulk of the MHP film, introducing passivation interlayers at the top contact, exploiting hydrophobic CTLs, and encapsulating finished devices with hydrophobic barrier layers, without jeopardizing device performance. Here, existing strategies for enhancing the performance stability of PSCs are reviewed and pathways toward moisture-resilient commercial perovskite devices are formulated.

Large‐Area Metal Halide Perovskite Photovoltaics Based on Solvent Bathing and Solution Bathing

Perovskite solar cells as one of the most promising photovoltaic technologies for commercialization have attracted tremendous attention in recent years. It is of great significance to develop and obtain a new controllable technology for preparing large‐area high‐quality perovskite thin films for promoting industrialization. The key to realizing high‐performance large‐area perovskite photovoltaic devices lies in the controllable preparation of large‐area perovskite active layers. Solvent bathing and solution bathing methods are new technologies suitable for large‐scale production, which can realize the controllability of large‐area and high‐quality perovskite layers and have the scalability, simplicity, and applicability required by industrialization. Herein, the research progress of large‐area metal halide perovskite films prepared by solvent bathing and solution bathing is emphasized. The crystallization kinetics of perovskite films prepared by solvent bathing is first introduced, including the types of antisolvents and the basis for screening. The next section illustrates the crystallization kinetics of solution bathing. Third, large‐area perovskite devices based on solvent bathing and solution bathing are present. Finally, the advantages and problems of this technology are summarized and future application scenarios are studied.

Optimized Substrate Orientations for Highly Uniform Metal Halide Perovskite Film Deposition.

Uniform optoelectronic quality of metal halide perovskite (MHP) films is critical for scalable production in large-area applications, such as photovoltaics and displays. While vapor-based MHP film deposition is advantageous for this purpose, achieving film uniformity can be challenging due to uneven temperature distribution and precursor concentration over the substrate. Here, we propose optimized substrate orientations for the vapor-based fabrication of homogeneous MAPbI3 thin films, involving a PbI2 primary layer deposition and subsequent conversion using vaporized methylammonium iodide (MAI). Leveraging computational fluid dynamics (CFD) simulations, we confirm that vertical positioning during the PbI2 layer growth yields a uniform film with a narrow temperature distribution and minimal boundary layer thickness. However, during the subsequent conversion step, horizontal substrate positioning results in spatially more uniform MAPbI3 thickness and grain size compared to the vertical placement due to enhanced MAI intercalation. From this optimized substrate positioning, we observe substantial optical homogeneity across the substrate on a centimeter scale, along with uniform and enhanced optoelectronic device performance within photodetector arrays. Our results offer a potential path toward the scalable production of highly uniform perovskite films.

Moisture control enables high-performance sprayed perovskite solar cells under ambient conditions

Morphology and crystallization control are critical for metal halide perovskite films in enabling high-performance photovoltaic devices. However, they remain particularly challenging for sprayed devices due to the inherent flaw of the spraying technology—the “coffee-ring” effect (CRE). Herein, we report a moisture-assisted strategy that effectively eliminates CRE and enhances film crystallization through the combined utilization of humidity control and water additives. This approach leads to the formation of Cs0.19FA0.81PbI2.5Br0.5 perovskite films with homogeneous morphology and excellent crystallization, and the power conversion efficiency (PCE) of the champion perovskite solar cells increases from 18.25% to 19.74%. Moreover, unencapsulated devices exhibit excellent stability, with 80% of their initial efficiency retained after operating at 50 °C for over 800 h. Furthermore, the large-area perovskite film (10 × 10 cm2) exhibits significant uniformity throughout the entire film, and the corresponding devices exhibit high consistency and reproducibility. The small-area devices utilizing the same large-area perovskite film show an average PCE of 19.53 ± 0.25%, while mini-modules with an active area of 64.8 cm2 yield an optimal PCE of 16.75%, with an average PCE of 16.08 ± 0.32%.

Al2O3 nanoparticles as surface modifier enables deposition of high quality perovskite films for ultra-flexible photovoltaics

Advanced photovoltaics, such as ultra-flexible perovskite solar cells (UF-PSCs), which are known for their lightweight design and high power-to-mass ratio, have been a long-standing goal that we, as humans, have continuously pursued. Unlike normal PSCs fabricated on rigid substrates, producing high-efficiency UF-PSCs remains a challenge due to the difficulty in achieving full coverage and minimizing defects of metal halide perovskite (MHP) films. In this study, we utilized Al2O3 nanoparticles (NPs) as an inorganic surface modifier to enhance the wettability and reduce the roughness of poly-bis(4-phenyl) (2,4,6-trimethylphenyl) amine simultaneously. This approach proves essentials in fabricating UF-PSCs, enabling the deposition of uniform and dense MHP films with full coverage and fewer defects. We systematically investigated the effect of Al2O3 NPs on film formation, combining simulation with experiments. Our strategy not only significantly increases the power conversion efficiency (PCE) from 11.96% to 16.33%, but also promotes reproducibility by effectively addressing the short circuit issue commonly encountered in UF-PSCs. Additionally, our UF-PSCs demonstrates good mechanical stability, maintaining 98.6% and 79.0% of their initial PCEs after 10,000 bending cycles with radii of 1.0 and 0.5 ​mm, respectively.

Passivating detrimental grain boundaries in perovskite films with strongly interacting polymer for achieving high-efficiency and stable perovskite solar cells

The grain boundaries in polycrystalline metal-halide perovskite films contain numerous defects, which contribute to performance loss and degradation in perovskite solar cells. In this study, we report a cyano-containing conjugated polymer, composed of benzodithiophene and bicyanobenzothiadiazole (PBDT2CNBT), that functionalizes perovskite crystalline domains for defect passivation and charge carrier extraction. We demonstrate that cyano groups can effectively passivate these defects through strong interactions between the conjugated polymer and perovskite components. The PBDT2CNBT polymer not only modifies the perovskite film surface but also infiltrates the grain boundaries during perovskite crystallization. Notably, these conjugated polymers create favorable energy band bending at the boundary interface between the perovskite and conjugated polymer, enhancing charge separation and collection through grain boundaries by forming a cascade energy level structure. Consequently, we show that PBDT2CNBT transforms the intrinsically detrimental grain boundary into a beneficial feature for defect-free properties and improved charge collection. These advantages directly contribute to achieving high power conversion efficiencies of up to 22.9% and enhanced light, humidity, and thermal stability in perovskite solar cells. This study offers a novel strategy for developing multifunctional conjugated polymers for next-generation perovskite optoelectronics.

Inverted Perovskite Solar Cells with >85% Fill Factor via Sequential Interfacial Engineering

Even the most efficient inverted p–i–n architecture perovskite solar cells (PSCs) are still inferior to those with regular n–i–p architecture, which is mainly limited by interfacial loss. Herein, both wet and dry metal–halide perovskite films are regulated through organic molecules–assisted sequential interfacial engineering for high‐performance inverted PSCs. In specific, organic acetic acid treatment on the wet film potently regulates the nucleation and crystallization of perovskite films. Then, further loading 4‐(dimethylamino)benzoic acid on the dry perovskite film creates a passivating agent layer to suppress defect formation, leading to more phase‐pure and conductive perovskite films. Combined experimental and theoretical results illustrate that such sequential treatment is beneficial for decreasing surface trap states, non‐radiative recombination, and carrier transport loss. As a result, the target inverted PSC exhibits an unprecedented high fill factor (FF) of 85.31% together with a champion efficiency of 21.37%, which is greatly improved relative to the reference (FF of 79.60%, and efficiency of 19.40%). It should be noted that such a high FF is among the highest report and corresponding to 94.38% of the Shockley–Queisser limited FF (90.39%) of PSCs with a bandgap of 1.576 eV. In addition, the storage stability against moisture of target inverted PSCs is remarkably enhanced.

Epitaxial inorganic metal-halide perovskite films with controlled surface terminations

Metal-halide perovskite (MHP) thin films for next-generation solar cells are typically fabricated by wet-chemical synthesis in which surface properties such as the orientation of surface facets and their termination cannot be controlled. MHP device efficiencies depend critically on those surface properties. We demonstrate the epitaxial growth of several nanometer thick purely (001)-orientated films of ${\mathrm{CsPbBr}}_{3}$ and ${\mathrm{CsSnBr}}_{3}$ MHPs on Au(001) by molecular beam epitaxy. The epitaxial films are in a cubic phase aligned with the substrate. Their surfaces are singly terminated and can be modified for the first time. While the CsBr and ${\mathrm{PbBr}}_{2}$ surface terminations differ in terms of their atomic structure and defect content, the films are intrinsic semiconductors irrespective of the termination. The work function of the ${\mathrm{PbBr}}_{2}$-terminated surface is increased by $0.7\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$, which has drastic implications for the level alignment at MHP interfaces.

Separate observation of surface passivation and linking effects of oleylamine alkylamine ligands on metal-halide perovskite films

Separate observation of surface passivation and linking effects of oleylamine alkylamine ligands on metal-halide perovskite films

Thermochromic Halide Perovskite Windows with Ideal Transition Temperatures

AbstractUrban centers across the globe are responsible for a significant fraction of energy consumption and CO2 emission. As urban centers continue to grow, the popularity of glass as cladding material in urban buildings is an alarming trend. Dynamic windows reduce heating and cooling loads in buildings by passive heating in cold seasons and mitigating solar heat gain in hot seasons. Here, reduced energy consumption in highly glazed buildings in a mesoscopic building energy model is demonstrated when thermochromic windows are employed. Savings are realized across eight disparate climate zones of the United States. The model is used to determine ideal critical transition temperatures of 20–27.5 °C for thermochromic windows based on metal halide perovskite materials. Ideal transition temperatures are realized experimentally in composite metal halide perovskite films composed of perovskite crystals and an adjacent reservoir phase. The transition temperature is controlled by cointercalating methanol, instead of water, with methylammonium iodide and tailoring the hydrogen‐bonding chemistry of the reservoir phase. Thermochromic windows based on metal halide perovskites represent a clear opportunity to mitigate the effects of energy‐hungry buildings.

Efficient Perovskite Light-Emitting Diodes by Buried Interface Modification with Triphenylphosphine Oxide.

Metal halide perovskite films are prepared mainly by solution-based methods. However, the preparation process is prone to produce massive defects at the interface between the perovskite emitting layer and the charge transport layers, limiting the perovskite light-emitting diode device performance. Aiming at this problem, researchers have proposed many effective strategies to passivate these interface defects. However, most previous research studies only focus on modifying the perovskite top interface, and very few reports deal with the buried interface. Here, we deposited triphenylphosphine oxide (TPPO) molecules between the perovskite and the hole transport layer (HTL) and realized the buried interface modification. Adding TPPO avoids the contact recombination of the perovskite and HTL and improves the film quality by increasing the substrate wettability. Moreover, the lone pair electrons of P═O can interact with the uncoordinated lead (Pb2+) of the perovskite and passivate halogen vacancy defects, and the insulation property of TPPO helps to balance the injection of holes and electrons. As a result, a maximum external quantum efficiency (EQEmax) of 21.01% was obtained with an average of 18.4 ± 0.9% over 30 devices, and the device reproducibility was greatly enhanced.