Periodic Reporting for period 1 - FASTEST (Fully Air-Processable and Air-Stable Perovskite Solar Cells Based on Inorganic Metal Halide Perovskite Nanocrystals)
Período documentado: 2018-09-01 hasta 2020-08-31
- The issue to be addressed
Recently, the emerging photovoltaic technology based on organic metal halide (OMH) perovskite has attracted a lot of interest due to its significant increase in power conversion efficiency up to 22%. Metal halide perovskites are crystalline materials with the chemical formula ABX3, where A and B are cations and X is an anion, and the overall charge of the resulting crystal is zero. However, under the scene of prosperity, many problems still remain unsolved, especially the instability of OMH-perovskite. The extreme sensitivity to oxygen and moisture incurs the constraint of a critical environment for storage, fabrication, and device operation. The notorious problems of photo and thermal stabilities in omh-perovskite materials are also observed due to the instability of organic groups. Moreover, the unavoidable generation of defects and grain boundaries which formed in the process of perovskite film formations reduce the quality of perovskite films and further affect optoelectronic properties of the resulting films. Metal halide perovskite nanocrystals (NCs) have gathered immense attention as materials with highly tunable chemistry and unique optoelectronic properties such as the so-called defect tolerance. They have been implemented in a variety of optoelectronic applications, like light-emitting diodes, solar cells, white phosphors, and solar concentrators. Among them, the Cs based all-inorganic lead halide perovskites, CsPbX3 (X = I, Br, Cl), without a volatile organic component, has resulted of particular interest due to their high potential in terms of thermal stability. However, they suffer of severe chemical and phase stability, especially when targeting narrower bandgap semiconductors because iodide-containing inorganic perovskite could be easily degraded to nonphotoactive δ-phase under illumination in ambient conditions.
- The overall objectives
FASTEST project aims to develop fully air-stable inorganic metal halide perovskite NCs-based solar cells. It developed strategies for producing air-stable inorganic metal halide perovskite NCs using RT synthesis method. The ligand structure was controlled to make crystal structure suitable for absorption and charge transport. Along with that, chemical doping with a mixed halide ions was incorporated to retain the phase stability and to access the optimized band gap energy for single junction solar cells around 1.9 eV. The synthesized NCs are applied for photovoltaic devices to demonstrate its enhanced operational stability under continuous illumination.
- Importance of this project for society
This kind of perovskite nanomaterials are cheap to produce and relatively simple to manufacture especially in the shape of nanocrystals. Perovskites provides a bright future promise for solid-state solar cells due to the intrinsic properties: for example, tunable absorption spectrum, fast charge separation, long transport distance of electrons and holes. Therefore, perovskite solar cells are the rising star in the field of photovoltaics. They are causing excitement within the solar power industry with their ability to absorb light across almost all visible wavelengths, exceptional power conversion efficiencies already exceeding 20% in the lab, and relative ease of fabrication. Perovskite solar cells still face several challenge, but much work such as this FASTEST project is put into facing them and some companies, are already talking about commercializing them in the near future.
Recently, the emerging photovoltaic technology based on organic metal halide (OMH) perovskite has attracted a lot of interest due to its significant increase in power conversion efficiency up to 22%. Metal halide perovskites are crystalline materials with the chemical formula ABX3, where A and B are cations and X is an anion, and the overall charge of the resulting crystal is zero. However, under the scene of prosperity, many problems still remain unsolved, especially the instability of OMH-perovskite. The extreme sensitivity to oxygen and moisture incurs the constraint of a critical environment for storage, fabrication, and device operation. The notorious problems of photo and thermal stabilities in omh-perovskite materials are also observed due to the instability of organic groups. Moreover, the unavoidable generation of defects and grain boundaries which formed in the process of perovskite film formations reduce the quality of perovskite films and further affect optoelectronic properties of the resulting films. Metal halide perovskite nanocrystals (NCs) have gathered immense attention as materials with highly tunable chemistry and unique optoelectronic properties such as the so-called defect tolerance. They have been implemented in a variety of optoelectronic applications, like light-emitting diodes, solar cells, white phosphors, and solar concentrators. Among them, the Cs based all-inorganic lead halide perovskites, CsPbX3 (X = I, Br, Cl), without a volatile organic component, has resulted of particular interest due to their high potential in terms of thermal stability. However, they suffer of severe chemical and phase stability, especially when targeting narrower bandgap semiconductors because iodide-containing inorganic perovskite could be easily degraded to nonphotoactive δ-phase under illumination in ambient conditions.
- The overall objectives
FASTEST project aims to develop fully air-stable inorganic metal halide perovskite NCs-based solar cells. It developed strategies for producing air-stable inorganic metal halide perovskite NCs using RT synthesis method. The ligand structure was controlled to make crystal structure suitable for absorption and charge transport. Along with that, chemical doping with a mixed halide ions was incorporated to retain the phase stability and to access the optimized band gap energy for single junction solar cells around 1.9 eV. The synthesized NCs are applied for photovoltaic devices to demonstrate its enhanced operational stability under continuous illumination.
- Importance of this project for society
This kind of perovskite nanomaterials are cheap to produce and relatively simple to manufacture especially in the shape of nanocrystals. Perovskites provides a bright future promise for solid-state solar cells due to the intrinsic properties: for example, tunable absorption spectrum, fast charge separation, long transport distance of electrons and holes. Therefore, perovskite solar cells are the rising star in the field of photovoltaics. They are causing excitement within the solar power industry with their ability to absorb light across almost all visible wavelengths, exceptional power conversion efficiencies already exceeding 20% in the lab, and relative ease of fabrication. Perovskite solar cells still face several challenge, but much work such as this FASTEST project is put into facing them and some companies, are already talking about commercializing them in the near future.
"Inorganic perovskite nanocrystals (NCs) have shown good potential as an emerging semiconducting building block owing to their excellent optoelectronic properties. Despite extensive studies on their structure-dependent optical properties, they still suffer severely from chemical and phase instabilities in ambient condition. Here we report a facile method for the synthesis of mixed halide inorganic perovskite NCs based on recrystallization in an antisolvent mixture in ambient atmosphere, at room temperature. We introduced an alcohol-derivative solvent, as a secondary antisolvent in the solvent mixture, which significantly facilitates formation of perovskite crystallization with an improved chemical yield and stability. We demonstrate that this secondary antisolvent holds an intermolecular interaction with lead halide salt, which successfully stabilizes the dark phase of perovskite by encapsulating NCs in solution. This allows to produce concentrated NC solutions with a photoluminescence quantum yield of 70%. Finally, we fabricate CsPbI2Br NC solar cells which showed a stabilized photovoltaic performance in ambient condition, without encapsulation, showing a Voc of 1.32V with an optical bandgap of 1.88 eV.
Min Kim, Daniele Cortecchia, Tetiana Borzda, Wojciech Mroz, Luca Leoncino, David Dellasega, Annamaria Petrozza, ""Ligand-Like Antisolvent Assisting Crystallization of Stable CsPbI2Br Perovskite Nanocrystals for Photovoltaic Applications"" (in preparation)
These works were reported in various conferences such as (PSCO-2019, MRS Fall 2018, PSCO-2018) and will be published soon in peer-reviewed journals."
Min Kim, Daniele Cortecchia, Tetiana Borzda, Wojciech Mroz, Luca Leoncino, David Dellasega, Annamaria Petrozza, ""Ligand-Like Antisolvent Assisting Crystallization of Stable CsPbI2Br Perovskite Nanocrystals for Photovoltaic Applications"" (in preparation)
These works were reported in various conferences such as (PSCO-2019, MRS Fall 2018, PSCO-2018) and will be published soon in peer-reviewed journals."
The stability of perovskite solar cells is still largely lagging behind the most widely used silicon photovoltaics. For successful commercialization, the T80 lifetime (took until it decays to 80%) should be over 20 years. But, the state-of-the-art perovskite solar cell shows 2000 hours at most. In this project, we achieved a T80 of 500 hours from a defect-passivated perovskite solar cell that was operating under continuous illumination in an ambient condition. This specific value is not enough to compete with other stable photovoltaics yet. However, this FATEST project provides plentiful insight for improving the stability of perovskite: for example, surface-passivation of defective perovskite by using functional organic material, perovskite nanocrystals encapsulated by strongly binding ligands, and high-throughput production of nanocrystals from the room-temperature process. By combining all the strategies to enhance the stability of perovskite material, we expect that the fully passivated perovskite would show enhanced durability for photovoltaic applications as well as other optoelectronic device applications. Furthermore, we will grasp a full understanding of the degradation mechanism of perovskite solar cells under various environmental stresses.
This project will have an impact on perovskite production in terms of the costs of solar power. Perovskite solar cells are drawing expectations for the material’s desirable properties including excellent light absorption, low manufacturing cost, and ease of scalability for large-scale production. They have become the fastest advancing not only due to the technologically promising nature of Perovskites, but also thanks to their commercial advantage. The materials are widely available and relatively cheap compared to conventional silicon-based solar cells. This low-cost production of perovskite solar cells will make it possible to implement photovoltaic energy source to any part of our everyday lives: for example, building-integrated photovoltaics, Solar-energy-driven urban engineering, Vehicles powered by photovoltaics, and lightweight mobile energy charger. We believe it will change our lifestyle to have ubiquitous solar energy sources.
This project will have an impact on perovskite production in terms of the costs of solar power. Perovskite solar cells are drawing expectations for the material’s desirable properties including excellent light absorption, low manufacturing cost, and ease of scalability for large-scale production. They have become the fastest advancing not only due to the technologically promising nature of Perovskites, but also thanks to their commercial advantage. The materials are widely available and relatively cheap compared to conventional silicon-based solar cells. This low-cost production of perovskite solar cells will make it possible to implement photovoltaic energy source to any part of our everyday lives: for example, building-integrated photovoltaics, Solar-energy-driven urban engineering, Vehicles powered by photovoltaics, and lightweight mobile energy charger. We believe it will change our lifestyle to have ubiquitous solar energy sources.