 The researchers developed a new method to create a hydrogen-dope titanium dioxide, HTO, film that can be used as an efficient electron transport material for flexible and tandem perovskite solar cells. This film has a higher conductivity than other films created using conventional methods, allowing for faster electron extraction from the perovskite photo absorber. Additionally, this film has an upward shifted Fermi level, which leads to less loss on voltage open circuit and facilitates the growth of high-quality perovskite with large grain sizes and more uniform size. As a result, these devices show a significant improvement in performance compared to devices made with untreated titanium dioxide. This article was authored by Exan Yao, Jun Wiliang, Wa Longli, and others.