FASTEST · Fully Air-Processable and Air-Stable Perovskite Solar Cells Based on Inorganic Metal Halide Perovskite Nanocrystals

Fully Air-Processable and Air-Stable Perovskite Solar Cells Based on Inorganic Metal Halide Perovskite Nanocrystals

- 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.

Data: CORDIS, © European Union