Accessing Metal‐Containing Species in Tin–Lead Perovskite Precursor Solutions via Molecular Strategies Guided by the Hard–Soft Acid–Base Principle
Shuaifeng Hu, Xinru Sun, Wentao Liu, Luca Gregori, Pei Zhao, Jorge M. Pascual, André Dallmann, Akash Dasgupta, Fengjiu Yang, Guixiang Li, Mahmoud H. Aldamasy, Silver‐Hamill Turren‐Cruz, Marion A. Flatken, Sheng Fu, Yasuko Iwasaki, Richard Murdey, Armin Hoell, Susan Schorr, Steve Albrecht, Shangfeng Yang, Antonio Abate, Atsushi Wakamiya, Filippo De Angelis, Meng Li, Henry J. Snaith
Abstract
Abstract The properties of metal‐centred species in metal halide perovskite precursor solutions substantially influence the formation and evolution of colloidal particles, which in turn dictate the crystallisation process and the film quality. In this work, we assess the “hard” and “soft” Lewis acid characteristics of Sn 2+ and Pb 2+ cations as a strategy to modulate the chemical environment of these metal‐containing species in mixed‐metal tin–lead perovskite precursor solutions. We observe enhanced simultaneous access to both metal centres upon adding compounds with functional groups suggested by the hard–soft acid–base principle. Theoretical calculations suggest that the hard base carboxyl group preferentially interacts with Sn 2+ ‐based species, while the softer base thiol group also targets Pb 2+ ‐based species. By effectively accessing and manipulating possible classes of inorganic species and their colloidal particle properties in the precursor solutions, we achieve 1.26 eV perovskite polycrystalline films exhibiting enhanced structural and optoelectronic quality, giving the best quasi‐Fermi level splitting values of up to 0.95 eV. As a result, the solar cell devices demonstrate efficiency values of up to 23.3% with an extended operational lifetime, retaining 80% of their initial efficiency after over 280 and 180 h of maximum power point tracking under simulated AM1.5G illumination at 25 and 65 °C, respectively.