High-efficiency and stable FA0.75MA0.25SnI3 perovskite solar cells with large-size crystal grains prepared by doping with multifunctional chloride salt

Abstract

Although tin (Sn)-based perovskite stands out among numerous lead-free perovskite materials due to its suitable band gap and low toxicity, Sn-based perovskite solar cells (PSCs) still have problems with excessive internal defects and poor stability. Here, we introduce a passivation material 1,2,4,5-benzenetetramine tetrahydrochloride (C₆H₂(NH₂)₄·4HCl) with Cl⁻ and –NH₃⁺ into the FA_0.75MA_0.25SnI₃ perovskite. The research results indicate that the introduction of Cl can promote the generation of large-sized grains. The introduction of C₆H₂(NH₂)₄·4HCl through NH⋯I can effectively passivate the internal defects of perovskite films and capture free I⁻, thereby improving the crystallinity and quality of the films. By adjusting and optimizing the concentration of C₆H₂(NH₂)₄·4HCl, the light absorption of the FA_0.75MA_0.25SnI₃ film with the addition of 0.7 mol% C₆H₂(NH₂)₄·4HCl additive was enhanced, the defect density and unnecessary non-radiative recombination were reduced, and the oxidation of Sn²⁺ was inhibited. Finally, the C₆H₂(NH₂)₄·4HCl-incorporated FA_0.75MA_0.25SnI₃ device achieved the best power conversion efficiency (PCE) of 9.83%, and remained at an initial efficiency of 80% after being placed in a glove box under an N₂ environment for 850 hours (not encapsulated).