Siraj Sidhik and Yafei Wang have successfully achieved High-phase purity 2D perovskite films with near-perfect vertical orientation using Lithium doped nickel oxide as the hole transport layer. They demonstrate that 2D PSCs with Li-doped NiOX exhibit excellent photostability, with T99 = 400 h at 1 sun and T90 of 100 h at 5 suns measured at a relative humidity of…