Additive Engineering with Triple Cations and Bifunctional Sulfamic Acid for Tin Perovskite Solar Cells Attaining a PCE Value of 12.5% without Hysteresis

Abstract

Imidazolium (IM) and cesium (Cs) were treated as A-site cationic additives for a triiodide tin perovskite solar cell (FASnI 3 ; FA, formamidinium) with sulfamic acid (SA) as a bifunctional additive in varied proportions. IM has a tight aromatic structure that is feasible to passivate the crystal defects and help in perovskite crystallization. Cs can stabilize the crystal structure and decrease trap state densities. TOF-SIMS measurements show the passivation effect of both IM and SA occurring on the surface of the film. The bifunctional SA additive can occupy the iodine vacancies in tin perovskites to passivate the uncoordinated Sn atoms and to passivate the surface defects effectively. Furthermore, SA has the effect of reducing Sn 4+ back to Sn 2+ via its ammonia/ acid form converted from its zwitterionic form upon irradiation, as observed from in situ XPS measurements. The hybrid device was optimized to attain a PCE value of 12.5% for the perovskite structure Cs 0.02 IM 0.1 FA 0.88 SnI 3 +1% SA with superior, long-lasting stability.

Oriented Attachment of Tin Halide Perovskites for Photovoltaic Applications

“…Numerous works have been devoted to enhancing the crystal quality of THPs by controlling the crystallization processes of THP films. − For instance, Hao et al revealed that an intermediate solvate SnI 2 ·3DMSO could form to reduce the crystal growth rate of THPs when dimethyl sulfoxide (DMSO) was chosen as the solvent of a THP precursor solution . Jokar et al reported that the nucleation sites of THPs increased after introducing EDAI 2 in the FASnI 3 (FA: formamidinium) film, resulting in uniform and dense THP films .…”

Emerging Opportunities in Lead-Free and Lead–Tin Perovskites for Environmentally Viable Photodetector Applications

“… Crystal structure. The crystal structure plays a critical role in stabilizing tin perovskite, as it affects the defect formation energy and band alignment. ,,,− Mixing different cations in the perovskite structure has been shown to decrease the crystal strain and increase the defect formation energy, leading to improved stability. ,,− Recent studies have demonstrated that adding larger organic cations, such as guanidinium, , azetidinium, or imidazolium, to the perovskite precursor solution can enhance the stability and increase the defect formation energy. Introducing bulky organic cations with heteroatoms can also affect the crystal formation energy, leading to improved stability.…”

Molecular interaction modulating Ruddlesden–Popper tin-based perovskite crystallization

“…Several efforts have been made to control the crystallization process of RP tin-based perovskites via additives, 12–14 solvents, 15,16 and composition engineering. 17,18 For example, poly(4-vinylphenol) and poly(vinyl pyrrolidone) were employed to increase nucleation sites, improving the morphology and crystallization of RP tin-based perovskite films.…”

“…8,9 Currently, the highest reported photovoltaic efficiency based on 2D RP tin halide perovskite (n = 4) is 10.36%, 10 far lower than its Shockley-Queisser limit value (∼32%). 11 Several efforts have been made to control the crystallization process of RP tin-based perovskites via additives, [12][13][14] solvents, 15,16 and composition engineering. 17,18 For example, poly (4vinylphenol) and poly(vinyl pyrrolidone) were employed to increase nucleation sites, improving the morphology and crystallization of RP tin-based perovskite lms.…”