Lights and Shadows of DMSO as Solvent for Tin Halide Perovskites

Abstract

In 2020 dimethyl sulfoxide (DMSO), the ever-present solvent for tin halide perovskites, was identified as an oxidant for Sn II . Nonetheless, alternatives are lacking and few efforts have been devoted to replacing it. To understand this trend it is indispensable to learn the importance of DMSO on the development of tin halide perovskites. Its unique properties have allowed processing compact thin-films to be integrated into tin perovskite solar cells. Creative approaches for controlling the perovskite crystallization or increasing its stability to oxidation have been developed relying on DMSObased inks. However, increasingly sophisticated strategies appear to lead the field to a plateau of power conversion efficiency in the range of 10-15 %. And, while DMSO-based formulations have performed in encouraging means so far, we should also start considering their potential limitations. In this concept article, we discuss the benefits and limitations of DMSO-based tin perovskite processing.

New Pb-Free Stable Sn–Ge Solid Solution Halide Perovskites Fabricated by Spray Deposition

“…The advantage of spray deposition for Ge-containing HaPs over spin-coating is that spraying is possible with solutions of much lower concentrations than spin-coating, for forming well-covering continuous films and, as Ge precursors are poorly soluble in DMF, the low concentration solution is not suitable for spin-coating. We use DMF because use of DMSO with Sn precursors is considered to be oxidizing, which leads to a high concentration of Sn 4+ . While the Sn and Pb HaPs are spin-coated at 1–1.5 M, this is not possible for Ge-based HaPs .…”

“…We use DMF because use of DMSO with Sn precursors is considered to be oxidizing, which leads to a high concentration of Sn 4+ . 26 While the Sn and Pb HaPs are spincoated at 1−1.5 M, this is not possible for Ge-based HaPs. 27 SEM images of sprayed (Figure 1a) and spin-coated (Figure 1b) CsGeBr 3 in DMF are presented.…”

Pyridine Controlled Tin Perovskite Crystallization

“…However, Saidaminov et al and our group described its undesirable oxidizing nature when mixed with iodide salts. 20 , 21 For this reason, we recently proposed a new group of solvents as possible DMSO replacements without tin oxidation’s downside. 22 The selection of new solvents for processing THP is a complicated process as many different factors regarding both the chemical and physical properties of the solvents must be considered, for example, the solubility of the precursors, the vapor pressure of the solvents, and the formation of stable complexes with the organic and inorganic components of the salts.…”

“…Dimethyl sulfoxide (DMSO) is the most used solvent for preparing both Pb and Sn perovskite thin films due to its favorable interaction with the perovskite precursors in solution, slowing down the crystallization process. However, Saidaminov et al and our group described its undesirable oxidizing nature when mixed with iodide salts. , For this reason, we recently proposed a new group of solvents as possible DMSO replacements without tin oxidation’s downside . The selection of new solvents for processing THP is a complicated process as many different factors regarding both the chemical and physical properties of the solvents must be considered, for example, the solubility of the precursors, the vapor pressure of the solvents, and the formation of stable complexes with the organic and inorganic components of the salts. − One possible approach is to search for an additive or a cosolvent forming a strong interaction with tin iodide salts.…”

Enabling water-free PEDOT as hole selective layer in lead-free tin perovskite solar cells

“…For instance, when introducing SnF 2 , 34,35 we obtained material with no detectable light emission. 33 Interestingly, the successful doping strategy we could transfer from the standard DMSObased processing is the introduction of ethylenediammonium diiodide (EDAI 2 ) into the perovskite composition. [36][37][38] Similarly to what was observed by Jokar et al, 36 we could keep a progressive enlargement of the perovskite bandgap upon introducing EDAI 2 , as visible from the blueshift of the PL peak maximum from 885 to 824 nm (see Fig.…”