Researchers of KIT and of two Helmholtz platforms have succeeded in finding a way to predict the quality of the perovskite layers. It is now possible assess their quality from variations in light emission already in the manufacturing process.
Perovskite tandem solar cells combine a perovskite solar cell with a conventional solar cell, for example based on silicon. These cells are considered a next-generation technology: They boast an efficiency of currently more than 33 %, which is much higher than that of conventional silicon solar cells. Moreover, they use inexpensive raw materials and are easily manufactured. To achieve this level of efficiency, an extremely thin high-grade perovskite layer, whose thickness is only a fraction of that of human hair, has to be produced. “Manufacturing these high-grade, multi-crystalline thin layers without any deficiencies or holes using low-cost and scalable methods is one of the biggest challenges,” says tenure-track professor Ulrich W. Paetzold who conducts research at the Institute of Microstructure Technology and the Light Technology Institute of KIT. Even under apparently perfect lab conditions, there may be unknown factors that cause variations in semiconductor layer quality: “This drawback eventually prevents a quick start of industrial-scale production of these highly efficient solar cells, which are needed so badly for the energy turnaround,” explains Paetzold.
AI Finds Hidden Signs of Effective Coating
To find the factors that influence coating, an interdisciplinary team consisting of the perovskite solar cell experts of KIT has joined forces with specialists for Machine Learning and Explainable Artificial Intelligence (XAI) of Helmholtz Imaging and Helmholtz AI at the DKFZ in Heidelberg. The researchers developed AI methods that train and analyze neural networks using a huge dataset. This dataset includes video recordings that show the photoluminescence of the thin perovskite layers during the manufacturing process. Photoluminescence refers to the radiant emission of the semiconductor layers that have been excited by an external light source. “Since even experts could not see anything particular on the thin layers, the idea was born to train an AI system for Machine Learning to detect hidden signs of good or poor coating from the millions of data items on the videos,” Lukas Klein and Sebastian Ziegler from Helmholtz Imaging at the DKFZ explain. To filter and analyze the widely scattered indications output by the Deep Learning AI system, the researchers subsequently relied on methods of Explainable Artificial Intelligence.