Researchers at GIST have developed a perovskite mini-module with 22.56% efficiency by improving the SnO2 electron transport layer with PEI, reducing defects and electron loss. The module retained 94% of its performance after 500 hours, showing potential for scalable, stable perovskite solar cells and modules. The team focused on engineering the interface of the electron transport layer to address non-uniformity issues and improve efficiency and stability. By incorporating PEI into the SnO2 layer, they were able to reduce electron loss, improve electrical environment at the interface, and facilitate smooth electron transport, leading to high-quality perovskite films suitable for mass production.