Recrystallizing Sputtered NiO<i><sub>x</sub></i> for Improved Hole Extraction in Perovskite/Silicon Tandem Solar Cells
Yongbin Jin, Huiping Feng, Yingji Li, Hong Zhang, Xuelin Chen, Yawen Zhong, Qinghua Zeng, Jiarong Huang, Yalian Weng, Jinxin Yang, Chengbo Tian, Jinyan Zhang, Liqiang Xie, Zhanhua Wei
Abstract
Abstract Sputtering nickel oxide (NiO x ) is a production‐line‐compatible route for depositing hole transport layers (HTL) in perovskite/silicon tandem solar cells. However, this technique often results in films with low crystallinity and structural flaws, which can impair electronic conductivity. Additionally, the complex surface chemistry and inadequate Ni 3+ /Ni 2+ ratio impede the effective binding of self‐assembled monolayers (SAMs), affecting hole extraction at the perovskite/HTL interface. Herein, these issues are addressed using a recrystallization strategy by treating sputtered NiO x thin films with sodium periodate (NaIO 4 ), an industrially available oxidant. This treatment improved crystallinity and increased the Ni 3+ /Ni 2+ ratio, resulting in a higher content of nickel oxyhydroxide. These enhancements strengthened the SAM's anchoring capability on NiO x and improved the hole extraction at the perovskite/HTL interface. Moreover, the NaIO 4 treatment facilitated Na + diffusion within the perovskite layer and minimized phase separation, thus improving device stability. As a result, single‐junction perovskite solar cells with a 1.68 eV bandgap achieve a power conversion efficiency (PCE) of 23.22% for an area of 0.12 cm 2 . Perovskite/silicon tandem cells with an area of 1 cm 2 reached a PCE of 30.48%. Encapsulated tandem devices retained 95% of their initial PCE after 300 h of maximum power point tracking under 1‐sun illumination at 25 °C.