High‐Performance Tin–Lead Mixed‐Perovskite Solar Cells with Vertical Compositional Gradient. Issue 6 (22nd December 2021)

• Record Type: Journal Article
• Authors: Cao, Jiupeng; Loi, Hok‐Leung; Xu, Yang; Guo, Xuyun; Wang, Naixiang; Liu, Chun‐ki; Wang, Tianyue; Cheng, Haiyang; Zhu, Ye; Li, Mitch Guijun; Wong, Wai‐Yeung; Yan, Feng
• Is Part Of: Advanced materials. Volume 34:Issue 6(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-12-22
• Subjects: compositional gradients -- heterojunctions -- perovskite solar cells -- Sn–Pb mixed perovskite; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.202107729
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: Sn–Pb mixed perovskites with bandgaps in the range of 1.1–1.4 eV are ideal candidates for single‐junction solar cells to approach the Shockley–Queisser limit. However, the efficiency and stability of Sn–Pb mixed‐perovskite solar cells (PSCs) still lag far behind those of Pb‐based counterparts due to the easy oxidation of Sn 2+ . Here, a reducing agent 4‐hydrazinobenzoic acid is introduced as an additive along with SnF2 to suppress the oxidation of Sn 2+ . Meanwhile, a vertical Pb/Sn compositional gradient is formed spontaneously after an antisolvent treatment due to different solubility and crystallization kinetics of Sn‐ and Pb‐based perovskites and it can be finely tuned by controlling the antisolvent temperature. Because the band structure of a perovskite is dependent on its composition, graded vertical heterojunctions are constructed in the perovskite films with a compositional gradient, which can enhance photocarrier separation and suppress carrier recombination in the resultant PSCs. Under optimal fabrication conditions, the Sn–Pb mixed PSCs show power conversion efficiency up to 22% along with excellent stability during light soaking. Abstract : 4‐Hydrazinobenzoic acid is introduced to enhance the efficiency and stability of Sn–Pb mixed‐perovskite solar cells. Moreover, a vertical compositional gradient with a continuous change of the Pb/Sn ratio is found in the Sn–Pb mixed‐perovskite films, leading to graded heterojunctions that are beneficial for photocarrier separation. The resultant devices show a record efficiency up to 22%.