The chemical instability of metal halide perovskite materials can be ascribed to their unique properties of softness, in which the chemical bonding between metal halide octahedral frameworks and ...cations is the weak ionic and hydrogen bonding as in most perovskite structures. Therefore, various strategies have been developed to stabilize the cations and metal halide frameworks, which include incorporating additives, developing two-dimensional perovskites and perovskite nanocrystals,
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Recently, the important role of utilizing steric hindrance for stabilizing and passivating perovskites has been demonstrated. In this perspective, we summarize the applications of steric hindrance in manipulating and stabilizing perovskites. We will also discuss how steric hindrance influences the fundamental kinetics of perovskite crystallization and film formation processes. The similarities and differences of the steric hindrance between perovskite solar cells and perovskite light emission diodes are also discussed. In all, utilizing steric hindrance is a promising strategy to manipulate and stabilize metal halide perovskites for optoelectronics.
Manipulation on steric hindrance can influence the fundamental kinetics of perovskite crystallization and film formation, therefore stabilizing and passivating perovskite structures, and promoting the commercialization of stable perovskite devices.
•An ultra-thin tetraethylammonium based perovskitoid layer was developed to stabilize MAPbI3 perovskite.•The crystal structure and growth orientation of tetraethylammonium based perovskitoid was ...investigated.•The perovskitoid layer can inhibit ion migration and passivate trap states.•A champion efficiency of 21.79% with enhanced stability was achieved for MAPbI3 perovskite.
The efficiency and stability of typical three-dimensional (3D) MAPbI3 perovskite-based solar cells are highly restricted, due to the weak interaction between methylammonium (MA+) and PbI64-octahedra in the 3D structure, which can cause the ion migration and the related defects. Here, we found that the in situ-grown perovskitoid TEAPbI3 layer on 3D MAPbI3 can inhibit the MA+ migration in a polar solvent, thus enhancing the thermal and moisture stability of perovskite films. The crystal structure and orientation of TEAPbI3 are reported for the first time by single crystal and synchrotron radiation analysis. The ultra-thin perovskitoid layer can reduce the trap states and accelerate photo-carrier diffusion in perovskite solar cells, as confirmed by ultra-fast spectroscopy. The power conversion efficiency of TEAPbI3-MAPbI3 based solar cells increases from 18.87% to 21.79% with enhanced stability. This work suggests that passivation and stabilization by in situ-grown perovskitoid can be a promising strategy for efficient and stable perovskite solar cells.
The crystal structure of TEAPbI3 perovskitoid illustrated by single crystal XRD suggested that this perovskitoid has much higher stability than 3D MAPbI3 perovskite. The in situ growth method demonstrated that the formed TEAPbI3 atomic layer on MAPbI3 perovskite can improve the efficiency and stability of MAPbI3 based perovskite solar cells. The formation of atomic perovskitoid layer can not only modify the work function and trap density of MAPbI3 film but also inhibit the MA+ cation migration. Display omitted
Here, an effective synergistic stabilization strategy using TBABr leads to in situ formation of 1D TBAPbI3 capping layer and Br-induced crystal secondary growth, which helps effectively passivate the ...defects of CsPbI3 perovskite for efficient and stable inorganic perovskite photovoltaics.
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Cesium lead iodide (CsPbI3) perovskite has gained great attention in the photovoltaic (PV) community because of its unique optoelectronic properties, good chemical stability and appropriate bandgap for sunlight harvesting applications. However, compared to solar cells fabricated from organic-inorganic hybrid perovskites, the commercialization of devices based on all-inorganic CsPbI3 perovskites still faces many challenges regarding PV performance and long-term stability. In this work, we discovered that tetrabutylammonium bromide (TBABr) post-treatment to CsPbI3 perovskite films could achieve synergistic stabilization with both TBA+ cation intercalation and Br-doping. Such TBA+ cation intercalation leads to one-dimensional capping with TBAPbI3 perovskite formed in situ, while the Br-induced crystal secondary growth helps effectively passivate the defects of CsPbI3 perovskite, thus enhancing the stability. In addition, the incorporation of TBABr can improve energy-level alignment and reduce interfacial charge recombination loss for better device performance. Finally, the highly stable TBABr-treated CsPbI3-based perovskite solar cells show reproducible photovoltaic performance with a champion efficiency up to 19.04%, while retaining 90% of the initial efficiency after 500 h storage without encapsulation.
An effective LC-MS based method for online characterization of low abundant structural isomers of N-linked glycans in biological therapeutics was developed. N-linked glycans of a recombinant ...monoclonal antibody were released by PNGase F and labeled with 2-aminobenzamide (2-AB) fluorescent tag. The labeled glycans were analyzed by online ultraperformance liquid chromatography-hydrophilic interaction liquid chromatography (UPLC-HILIC) coupled with mass spectrometry (MS). The glycan structure was characterized by MS n fragmentation in negative ion mode followed by identification of the signature D ions. The assignment included monosaccharide sequence and linkage information. The developed method successfully characterized structural isomers of A1G1F (assigned as terminal sialic acid attached in the 1,6 branch at 2,3 position), and A1G1F′ (assigned as terminal sialic acid attached in the 1,3 branch at 2,3 position). Moreover, using the same approach, previously unknown low abundant species were identified unambiguously. One such structural isomer at low level, terminal GlcNAc of G1F+GlcNAc, was identified to be linked at the 1,6 branch. Additionally, another low level structural isomer, previously assigned as Man8 glycan, was found to be Man7+Glc glycan as its 1,3 branch containing three mannoses and one terminal glucose. The identification was further confirmed by a purified α-1,2-endomannosidase enzyme to generate the cleavage of α-1,3 linked terminal disaccharides (Man+glucose). Using this approach, different lots or different CHO produced mAbs was thoroughly examined and found that the newly identified “Man8” (Man7+Glc) was also present in different batches and in some commercially available therapeutic mAbs.
Lead halide perovskites have been widely studied for successful photovoltaic applications because of their exceptional optoelectronic properties, high photoconversion efficiencies, facile solution ...process and low cost. However, both organic-inorganic hybrid perovskite and all-inorganic perovskite solar cells still face the challenges with respect to higher photovoltaic performances and long-term stabilities against various environmental factors. To address these stability issues, solution-processed colloidal perovskite nanocrystals have been introduced into perovskite solar cells either as the sole light absorber material, or a surface additive for bulk perovskite films. The incorporation of perovskite quantum dots onto bulk perovskite thin films has shown great potential on improving the band alignment in solar cell structures, passivating bulk and surface defects, and enhancing overall device performances. Here in this perspective, we summarize the recent development on integrating semiconductor nanocrystals, including perovskite and metal chalcogenide quantum dots, onto bulk perovskite thin films for solar cell device fabrication. We also highlight and provide an outlook of the ongoing research studies regarding how the function and mechanism of this nanocrystal incorporation, the distribution of the added components, as well as the processing route, the chemical composition and the morphology of the nanocrystal can affect the fabricated device performances.
Enhancing bulk perovskite photovoltaics by integrating perovskites and metal chalcogenide quantum dots.
Perovskite oxides with unique crystal structures and high defect tolerance are promising as atomic surface passivation layers for photoelectrodes for efficient and stable water splitting. However, ...controllably depositing and crystalizing perovskite-type metal oxides at the atomic level remains challenging, as they usually crystalize at higher temperatures than regular metal oxides. Here, we report a mild solution chemistry approach for the quasi-epitaxial growth of an atomic CaTiO3 perovskite layer on rutile TiO2 nanorod arrays. The high-temperature crystallization of CaTiO3 perovskite is overcome by a sequential hydrothermal conversion of the atomic amorphous TiOx layer to CaTiO3 perovskite. The atomic quasi-epitaxial CaTiO3 layer passivated TiO2 nanorod arrays exhibit more efficient interface charge transfer and high photoelectrochemical performance for water splitting. Such a mild solution-based approach for the quasi-epitaxial growth of atomic metal oxide perovskite layers could be a promising strategy for both fabricating atomic perovskite layers and improving their photoelectrochemical properties.
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Recently, lead halide perovskite solar cells have become a promising next-generation photovoltaics candidate for large-scale application to realize low-cost renewable electricity generation. Although ...perovskite solar cells have tremendous advantages such as high photovoltaic performance, low cost and facile solution-based fabrication, the issues involving lead could be one of the main obstacles for its commercialization and large-scale applications. Lead has been widely used in photovoltaics industry, yielding its environmental and health issues of vital importance because of the widespread application of photovoltaics. When the solar cell panels especially perovskite solar cells are damaged, lead would possibly leak into the surrounding environment, causing air, soil and groundwater contamination. Therefore, lots of research efforts have been put into evaluating the lead toxicity and potential leakage issues, as well as studying the encapsulation of lead to deal with leakage issue during fire hazard and precipitation in photovoltaics. In this review, we summarize the latest progress on investigating the lead safety issue on photovoltaics, especially lead halide perovskite solar cells, and the corresponding solutions. We also outlook the future development towards solving the lead safety issues from different aspects.
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•Lead in perovskite photovoltaics poses potential risks to human health and ecosystem.•Water-soluble and bioavailable lead that leaks from damaged PSCs is dangerous.•Fail-safe encapsulation and safe device configuration are developed for lead leakage.•End-of-life PSCs as hazardous wastes should be taken into account before commercialization.
Defect‐triggered phase degradation is generally considered as the main issue that causes phase instability and limited device performance for CsPbI3 inorganic perovskites. Here, a defect compensation ...in CsPbI3 perovskite through crystal secondary growth of inorganic perovskites is demonstrated, and highly efficient inorganic photovoltaics are realized. This secondary growth is achieved by a solid‐state reaction between a bromine salt and defective CsPbI3 perovskite. Upon solid‐state reaction, the Br− ions can diffuse over the entire CsPbI3 perovskite layer to heal the undercoordinated Pb2+ and conduct certain solid‐state I/Br ion exchange reaction, while the organic cations can potentially heal the Cs+ cation vacancies through coupling with PbI64− octahedra. The carrier dynamics confirm that this crystal secondary growth can realize defect compensation in CsPbI3. The as‐achieved defect‐compensated CsPbI3 not only improves the charge dynamics but also enhances the photoactive phase stability. Finally, the CsPbI3‐based solar cell delivers 20.04% efficiency with excellent operational stability. Overall, this work proposes a novel concept of defect compensation in inorganic perovskites through crystal secondary growth induced by solid‐state reaction that is promising for various optoelectronic applications.
Defect‐triggered phase degradation has become the main issue in the field of inorganic CsPbI3 perovskite. A crystal secondary growth of inorganic perovskites induced by a solid‐state reaction to achieve defect compensation in CsPbI3 perovskite is demonstrated. Finally, the defect‐compensated CsPbI3‐based solar cell delivers 20.04% efficiency with excellent operational stability.
Research on chemically stable inorganic perovskites has achieved rapid progress in terms of high efficiency exceeding 19% and high thermal stabilities, making it one of the most promising candidates ...for thermodynamically stable and high‐efficiency perovskite solar cells. Among those inorganic perovskites, CsPbI3 with good chemical components stability possesses the suitable bandgap (≈1.7 eV) for single‐junction and tandem solar cells. Comparing to the anisotropic organic cations, the isotropic cesium cation without hydrogen bond and cation orientation renders CsPbI3 exhibit unique optoelectronic properties. However, the unideal tolerance factor of CsPbI3 induces the challenges of different crystal phase competition and room temperature phase stability. Herein, the latest important developments regarding understanding of the crystal structure and phase of CsPbI3 perovskite are presented. The development of various solution chemistry approaches for depositing high‐quality phase‐pure CsPbI3 perovskite is summarized. Furthermore, some important phase stabilization strategies for black phase CsPbI3 are discussed. The latest experimental and theoretical studies on the fundamental physical properties of photoactive phase CsPbI3 have deepened the understanding of inorganic perovskites. The future development and research directions toward achieving highly stable CsPbI3 materials will further advance inorganic perovskite for highly stable and efficient photovoltaics.
The recent progress of CsPbI3 perovskite for highly efficient and stable photovoltaics is summarized. Furthermore, those important phase stabilization strategies for black‐phase CsPbI3 are also discussed. With the advancing of fundamental studies on CsPbI3 perovskite material properties, the CsPbI3 perovskite and other inorganic perovskites will become more and more promising for high‐efficiency and stable perovskite solar cells.
All‐inorganic perovskites have attracted increasing attention for applications in perovskite solar cells (PSCs) and optoelectronics, including light‐emitting devices (LEDs). Cesium lead halide ...perovskites with tunable I/Br ratios and a band gap aligning with the sunlight region are promising candidates for PSCs. Although impressive progress has been made to improve device efficiency from the initial 2.9 % with low phase stability to over 20 % with high stability, there are still questions regarding the perovskite crystal growth mechanism, especially at low temperatures. In this Minireview, we summarize recent developments in using an organic matrix, including the addition and use of organic ions, polymers, and solvent molecules, for the crystallization of black phase inorganic perovskites at temperatures lower than the phase transition point. We also discuss possible mechanisms for this low‐temperature crystallization and their effect on the stability of black phase perovskites. We conclude with an outlook and perspective for further fabrication of large‐scale inorganic perovskites for optoelectronic applications.
An organic matrix can assist the crystallization of all‐organic perovskites at temperatures lower than the phase transition point of black phase CsPbX3 perovskite. This low‐temperature crystallization takes place through the formation and decomposition of an intermediate state which is reminiscent of an organic–inorganic perovskite matrix.
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