Sidhik, SirajWang, YafeiLi, WenbinZhang, HaoZhong, XinjueAgrawal, AyushHadar, IdoSpanopoulos, IoannisMishra, AnamikaTraoré, BoubacarSamani, Mohammad H. K.Katan, ClaudineMarciel, Amanda B.Blancon, Jean-ChristopheEven, JackyKahn, AntoineKanatzidis, Mercouri G.Mohite, Aditya D.2021-12-152021-12-152021Sidhik, Siraj, Wang, Yafei, Li, Wenbin, et al.. "High-phase purity two-dimensional perovskites with 17.3% efficiency enabled by interface engineering of hole transport layer." <i>Cell Reports Physical Science,</i> 2, no. 10 (2021) Elsevier: https://doi.org/10.1016/j.xcrp.2021.100601.https://hdl.handle.net/1911/111788State-of-the-art p-i-n-based 3D perovskite solar cells (PSCs) use nickel oxide (NiOX) as an efficient hole transport layer (HTL), achieving efficiencies >22%. However, translating this to phase-pure 2D perovskites has been unsuccessful. Here, we report 2D phase-pure Ruddlesden-Popper BA2MA3Pb4I13 perovskites with 17.3% efficiency enabled by doping the NiOX with Li. Our results show that progressively increasing the doping concentration transforms the photoresistor behavior to a typical diode curve, with an increase in the average efficiency from 2.53% to 16.03% with a high open-circuit voltage of 1.22 V. Analysis reveals that Li doping of NiOX significantly improves the morphology, crystallinity, and orientation of 2D perovskite films and also affords a superior band alignment, facilitating efficient charge extraction. Finally, we 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 relative humidity of 60% ± 5% without the need for external thermal management.engThis is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Journal article1-s2-0-S2666386421003167-mainhttps://doi.org/10.1016/j.xcrp.2021.100601