Fluoride Chemistry in Tin Halide Perovskites

Abstract

Tin is the frontrunner for substituting toxic lead in perovskite solar cells. However, tin suffers the detrimental oxidation of SnII to SnIV. Most of reported strategies employ SnF2 in the perovskite precursor solution to prevent SnIV formation. Nevertheless, the working mechanism of this additive remains debated. To further elucidate it, we investigate the fluoride chemistry in tin halide perovskites by complementary analytical tools. NMR analysis of the precursor solution discloses a strong preferential affinity of fluoride anions for SnIV over SnII, selectively complexing it as SnF4. Hard X‐ray photoelectron spectroscopy on films shows the lower tendency of SnF4 than SnI4 to get included in the perovskite structure, hence preventing the inclusion of SnIV in the film. Finally, small‐angle X‐ray scattering reveals the strong influence of fluoride on the colloidal chemistry of precursor dispersions, directly affecting perovskite crystallization.

Stable Lead‐Free Tin Halide Perovskite with Operational Stability >1200 h by Suppressing Tin(II) Oxidation

“…Chemie recombination (Figure 2g). [18][19][20][21][22][23][24][25][26][27] In zero-dimensional perovskite, once carriers are photogenerated, excited-state electrons will be rapidly self-trapped by the distorted lattice and then release energy by recombination processes, which is the typical light-emitting mechanism of STEs. [28,29] To verify the origin of the broadband emission from the intrinsic STEs, we have implemented excitation power dependent PL measurement, which shows a linear dependence from 1.1 to 110.3 W cm À 2 (Figure 2f), demonstrating that the emission does not originate from permanent defects.…”

A Review of Three-Dimensional Tin Halide Perovskites as Solar Cell Materials

“…In the proposal, SnF 2 will make up for tin vacancies created by oxidation, thereby regulating intrinsic carrier density. A recent study found that fluorine plays a major role in the complexation of Sn(IV) and provision of antioxidative properties 156 .…”

A Selective Targeting Anchor Strategy Affords Efficient and Stable Ideal‐Bandgap Perovskite Solar Cells

“…[36,37] This is followed by the formation of Sn vacancies and introduction of additional p-type charge (Equation (1)). [38,39] Several efforts have been made to address this issue, such as Sn compensators strategy, [40,41] redox strategy, [42] core-shell [43] structure, and interface engineering; [44][45][46][47] II) overfast and uncontrolled crystalize process. The uncontrollable crystalize process [7,48,49] has been attributed to stronger reaction between Sn and organic component than that of Pb, [50] leading to inferior film quality and increasing defect density as well.…”