Intermediate Phase Suppression with Long Chain Diammonium Alkane for High Performance Wide‐Bandgap and Tandem Perovskite Solar Cells

Abstract Wide bandgap (WBG) perovskite can construct tandem cells with narrow bandgap solar cells by adjusting the band gap to overcome the Shockley−Queisser limitation of single junction perovskite solar cells (PSCs). However, WBG perovskites still suffer from severe nonradiative carrier recombination and large open‐circuit voltage loss. Here, this work uses an in situ photoluminescence (PL) measurement to monitor the intermediate phase evolution and crystallization process via blade coating. This work reports a strategy to fabricate efficient and stable WBG perovskite solar cells through doping a long carbon chain molecule octane‐1,8‐diamine dihydroiodide (ODADI). It is found that ODADI doping not only suppresses intermediate phases but also promote the crystallization of perovskite and passivate defects in blade coated 1.67 eV WBG FA_0.7Cs_0.25MA_0.05Pb(I_0.8Br_0.2)₃ perovskite films. As a result, the champion single junction inverted PSCs deliver the efficiencies of 22.06% and 19.63% for the active area of 0.07 and 1.02 cm², respectively, which are the highest power conversion efficiencies (PCEs) in WBG PSCs by blade coating. The unencapsulated device demonstrates excellent stability in air, which maintains its initial efficiency at the maximum power points under constant AM 1.5G illumination in open air for nearly 500 h. The resulting semitransparent WBG device delivers a high PCE of 20.06%, and the 4‐terminal all‐perovskite tandem device delivers a PCE of 28.35%.