CINE paper presents an industrial-friendly route for perovskite solar cells production
Perovskite solar cells may irrupt into the energy market in the near future. However, for this to happen, some challenges still need to be overcome. One of them is the production of these devices on an industrial scale. In fact, so far, there is no processes that meet all the necessary conditions for the industrial manufacture of these solar cells to become viable.
Now, a development carried out by CINE researchers and collaborators has taken an important step in this direction. The research was reported in an article featured on the cover of the journal Industrial & Engineering Chemistry Research (ACS Publications). “In our research we carried out the manufacturing process of perovskite solar cells using modifications that could be easily applicable in an industrial environment”, summarizes Adriano dos Santos Marques, first author of the work, which was developed during his PhD at Unicamp.
Perovskite solar cells are formed by a “sandwich” of layers of different materials. The main layers are the photoactive, formed by a perovskite film that absorbs sunlight and converts it into electrical charges, and the transport layers, that conduct these charges to the electrodes.
For the industrial production of these devices, the main challenge is to find processes that generate homogeneous and defect-free perovskite films. Methods of this type, especially spin coating, work very well on a laboratory scale, but they are not scalable. On the other hand, techniques capable of producing larger films and in large quantities do not generate the best perovskite films…
Thus, in this new work, the researchers started with a scalable technique, known as blade coating, and optimized it in order to obtain perovskites with the necessary quality to compose solar cells with good energy conversion efficiency.
As the name suggests, the technique is based on the action of a blade that, moved by a mechanical arm, uniformly spreads a solution over a substrate, forming a moist film. Film thickness is determined by several factors: solution concentration, blade movement speed, and the size of the gap between the blade and the substrate. To make perovskite films, the solution must contain the elements that will later form the perovskite (called precursors) and the solvent. Upon evaporating the solvent, the compound solidifies, forming the crystals that are typical of the perovskites structure.
And it is at this stage that the biggest challenge in the manufacture of these solar cells is found: mastering the crystallization of perovskite. In fact, when crystallization is slow, films are more defective. The problem can be solved by increasing the temperature of the process. However, this solution generates higher energy consumption and prevents the use of flexible materials as film substrates, as they deform with heat.
Considering these factors, the CINE researchers maintained a low deposition temperature (of 50 °C) and made adjustments to the composition of the solution, changing the solvents and precursors and regulating the proportion between them. After several attempts, the authors managed to generate perovskite films with the desired quality. What’s more, they were able to use the same low-temperature blade coating process to produce the charge transport layers. In this way, it was possible to use materials that are already used in the organic solar cell industry. Solar cells assembled with these layers reached an efficiency of 14.3% – a very positive result for a process that met, for the first time, so many conditions compatible with the environment of the photovoltaic industry.
Paper: Low-Temperature Blade-Coated Perovskite Solar Cells. Adriano S. Marques, Roberto M. Faria, Jilian N. Freitas, and Ana F. Nogueira. Ind. Eng. Chem. Res. 2021, 60, 19, 7145–7154. https://doi.org/10.1021/acs.
Link to the cover: https://pubs.acs.org/toc/iecred/60/19
CINE authors: Jilian Nei de Freitas (researcher at CTI Renato Archer and associate researcher at CINE) e Ana Flávia Nogueira (professor at UNICAMP, director and principal investigator at CINE).