Chemical bath deposition of planar nickel oxide films for inverted perovskite solar cells and mini‐modules

Chemical bath deposition (CBD) is an economical method for the large‐scale preparation of high‐quality inorganic transport layers. In the field of the n–i–p perovskite solar cells (PSCs), the devices based on n‐type CBD–SnO 2 /CBD–TiO 2 structures demonstrate significant advantages in efficiency and stability. However, using CBD method to deposit high‐quality planar p‐type NiO x is challenging due to the anisotropic growth of nickel‐based intermediate phase. Herein, NH 4 Cl additive is introduced to modulate the intermediate phase by adjusting the concentration of [Ni(H 2 O) x (NH 3 ) 6− x ] 2+ cations. As a result, dense and uniform NiO x films are finally obtained after thermal annealing. Simultaneously, the energy level and hole conductivity of NiO x materials are carefully controlled by adjusting the annealing temperature. Benefited from the excellent electronic properties of CBD–NiO x hole‐transport layer, the inverted PSCs based on MAPbI 3 , (FA 0.98 MA 0.02 ) 0.95 Cs 0.05 Pb(I 0.95 Br 0.05 ) 3 achieve the power conversion efficiency of 19.75% and 23.30%, respectively. Furthermore, the unencapsulated devices maintain over 90% of their initial efficiency after continuous operation for 700 h. Scaling up this novel intermediate phase regulation CBD method yields a mini‐module with an active area of 14 cm 2 , achieving an efficiency of 19.36%.