Methylammonium Chloride Induces Intermediate Phase Stabilization for Efficient Perovskite Solar Cells

This review article examines the current state of understanding in how metal halide perovskite solar cells can degrade when exposed to moisture, oxygen, heat, light, mechanical stress, and reverse bias. It also highlights strategies for improving stability, such as tuning the composition of the perovskite, introducing hydrophobic coatings, replacing metal electrodes with carbon or transparent conducting oxides, and packaging. The article concludes with recommendations on how accelerated testing should be performed to rapidly develop solar cells that are both extraordinarily efficient and stable.

Understanding Degradation Mechanisms and Improving Stability of Perovskite Photovoltaics.

A Review of Perovskites Solar Cell Stability

Conventional 3D organic-inorganic halide perovskites have recently undergone unprecedented rapid development. Yet, their inherent instabilities over moisture, light, and heat remain a crucial challenge prior to the realization of commercialization. By contrast, the emerging 2D Ruddlesden-Popper-type perovskites have recently attracted increasing attention owing to their great environmental stability. However, the research of 2D perovskites is just in their infancy. In comparison to 3D analogues, they are natural quantum wells with a much larger exciton binding energy. Moreover, their inner structural, dielectric, optical, and excitonic properties remain to be largely explored, limiting further applications. This review begins with an introduction to 2D perovskites, along with a detailed comparison to 3D counterparts. Then, a discussion of the organic spacer cation engineering of 2D perovskites is presented. Next, quasi-2D perovskites that fall between 3D and 2D perovskites are reviewed and compared. The unique excitonic properties, electron-phonon coupling, and polarons of 2D perovskites are then be revealed. A range of their (opto)electronic applications is highlighted in each section. Finally, a summary is given, and the strategies toward structural design, growth control, and photophysics studies of 2D perovskites for high-performance electronic devices are rationalized.

2D Ruddlesden-Popper Perovskites for Optoelectronics

Owing to inevitable thermal/moisture instability for organic–inorganic hybrid perovskites, pure inorganic perovskite cesium lead halides with both inherent stability and prominent photovoltaic performance have become research hotspots as a promising candidate for commercial perovskite solar cells. However, it is still a serious challenge to synthesize desired cubic cesium lead iodides (CsPbI3) with superior photovoltaic performance for its thermodynamically metastable characteristics. Herein, polymer poly-vinylpyrrolidone (PVP)-induced surface passivation engineering is reported to synthesize extra-long-term stable cubic CsPbI3. It is revealed that acylamino groups of PVP induce electron cloud density enhancement on the surface of CsPbI3, thus lowering surface energy, conducive to stabilize cubic CsPbI3 even in micrometer scale. The cubic-CsPbI3 PSCs exhibit extra-long carrier diffusion length (over 1.5 μm), highest power conversion efficiency of 10.74% and excellent thermal/moisture stability. This result provides important progress towards understanding of phase stability in realization of large-scale preparations of efficient and stable inorganic PSCs.

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Surface passivation engineering strategy to fully-inorganic cubic CsPbI 3 perovskites for high-performance solar cells

In recent years, organometal trihalide perovskites have emerged as promising materials for low-cost, flexible, and highly efficient solar cells. Despite their processing advantages, before the technology can be commercialized the poor stability of the organic–inorganic hybrid perovskite materials with regard to humidity, heat, light, and oxygen has be to overcome. Herein, we distill the current state-of-the-art and highlight recent advances in improving the chemical stability of perovskite materials by substitution of the A-cation and X-anion. Our hope is to pave the way for the rational design of perovskite materials to realize perovskite solar cells with unprecedented improvement in stability.

Stability of Perovskite Solar Cells: A Prospective on the Substitution of the A Cation and X Anion.

Organic–inorganic halide perovskite solar cells have recently attracted much attention due to their low-cost fabrication, flexibility, and high efficiency The power conversion efficiency achieved with such cells was over 22% in 2016 from an initial 381% in 2009, highlighting how the cells are now benefiting from the highly optimized morphology of perovskite films To date, a great number of approaches have been done to improve the morphology of perovskite films, in which additives play an important role in perovskite crystal growth and in the dynamics of the crystallinity, and thus the performance of perovskite solar cells Herein, we review the recent progress on additives, such as polymers, fullerene, metal halide salts, organic halide salts, inorganic acids, solvents, and nanoparticles, in improving the morphology of perovskite films in terms of the crystal growth, crystallization kinetics, and device performance We also discuss the importance of further understanding the fundamental homogeneous nucleation process by the use of additives Further innovation in terms of the additives could help to further develop high-performance devices with long-term stability for future practical applications of perovskite solar cells

Additive engineering for highly efficient organic–inorganic halide perovskite solar cells: recent advances and perspectives

Organic–inorganic hybrid lead halide perovskites (e.g., CH3NH3PbX3, X = Cl, Br, I) hold great promise in optoelectronic devices, e.g., solar cells. High-performance devices have been realized by controlling the perovskite surface morphology, grain size, and degree of crystallinity. However, the role of the components during film formation and crystallization remains mysterious. Here, we show the management of perovskite intermediates to construct perovskite films with uniform perovskite crystals and controlled surface morphology using methylammonium acetate (MAAc) to retard the reaction between PbI2 and MAI in the solution. The formation of MAPbI3 was allowed via the exchange of I− anions from the neighboring MAI molecules to the perovskite intermediate phases replacing Ac− anions. A highly efficient perovskite solar cell with a power conversion efficiency of 18.09% was achieved. The experimental and theoretical studies reveal that perovskite intermediates play an important role in facilitating homogeneous nucleation or modulating the crystallization kinetics. These results also provide important progress towards the understanding of perovskite intermediate phases for advancing the building of perovskite semiconductors.

Management of perovskite intermediates for highly efficient inverted planar heterojunction perovskite solar cells

Seit einigen Jahren entwickeln sich Metall-organische Trihalogenidperowskite zu aussichtsreichen Materialien fur kostengunstige, flexible und hocheffiziente Solarzellen. Vor einer moglichen gewerblichen Nutzung mussen aber fur die organisch-anorganischen Hybrid-Perowskitmaterialien trotz ihrer Verarbeitungsvorteile die Probleme einer schlechten Stabilitat gegen Feuchtigkeit, Warme, Licht und Sauerstoff gelost werden. Hier besprechen wir den aktuellen Stand der Forschung und behandeln aktuelle Fortschritte zum Verbessern der chemischen Stabilitat von Perowskit-Materialien durch Substitution von A-Kation und X-Anion. Dabei soll der Weg zu einem rationalen Design von Perowskit-Materialien geebnet werden, mit denen Perowskit-Solarzellen mit besserer Stabilitat erhalten werden konnen.

Stabilität von Perowskit‐Solarzellen: Einfluss der Substitution von A‐Kation und X‐Anion

The invention discloses a method for preparing a stable and high-efficiency two-dimensional layered perovskite solar cell, and the method is characterized in that the method achieves the growth of micron-order perovskite crystalline grains in the air through the continuous heating in the whole spin coating process, and achieves the preparation of a flat high-quality perovskite film and a stable and high-efficiency perovskite photovoltaic device. A continuous heating method in the whole spin coating process, which is disclosed by the invention, enables a solvent to quickly volatilize to speed up the growth and conversion of the crystalline grains, also facilitates the growth of two-dimensional layered perovskite in a direction perpendicular to a substrate, and finally forms a flat and denseuniform perovskite film. The method disclosed by the invention does not need inert atmosphere for protection, facilitates the preparation of the large-area perovskite, and reduces the cost.

Taotao Li

Papers

Stability of Perovskite Solar Cells: A Prospective on the Substitution of the A Cation and X Anion.

Additive engineering for highly efficient organic–inorganic halide perovskite solar cells: recent advances and perspectives

Management of perovskite intermediates for highly efficient inverted planar heterojunction perovskite solar cells

Stabilität von Perowskit‐Solarzellen: Einfluss der Substitution von A‐Kation und X‐Anion

Stable and high-efficiency two-dimensional layered perovskite solar cell and preparation method therefor