Effects of Alkyl Chain Length on Crystal Growth and Oxidation Process of Two-Dimensional Tin Halide Perovskites

Abstract

Two-dimensional (2D) Sn-based lead-free perovskites have attracted extensive attention because of their nontoxicity and wide light absorption. It has been proven that the introduced organic spacer cations in the perovskite crystal prevent Sn2+ from oxidation to Sn4+. However, the effects of the alkyl chain length of these cations on the perovskite properties are unclear. Here, we investigate the impacts of chain length on crystal orientation and phase distribution of 2D Sn-based perovskite films by employing different alkylamines spacer cations (butylamine, octylamine, and dodecylamine). With the increase of alkyl chain length, the phase distribution of 2D Sn-based perovskite crystals become disordered and less oriented. Therefore, benefiting from application of a short alkyl chain in the organic spacer cation (e.g., BA), we manage to retard the oxidation process of Sn2+ for better device performance. Our work provides systematic understanding of configuration and size of organic spacer cations, which will further contribute to highly stable and efficient lead-free perovskite solar cells.

Crystallization Kinetics Modulation of FASnI3 Films with Pre‐nucleation Clusters for Efficient Lead‐Free Perovskite Solar Cells

“…Compared to lead halide perovskites, the crystallization rate of tin halide perovskites is much faster due to their lower solubility in common solvents, [19, 20] leading to defect‐rich films of tin halide perovskites. Many efforts have been devoted to improving the crystalline quality of tin halide perovskites by regulating the nucleation and crystal growth processes of perovskite films [21–27] . For example, poly(vinyl alcohol) was introduced in the FASnI 3 (FA: formamidinium) film to increase nucleation sites, [21] resulting in pinhole‐free and uniform perovskite films.…”

“…employed dimethyl sulfoxide (DMSO) as the solvent, by forming a stable intermediate solvate SnI 2 ⋅3DMSO, to retard the crystal growth of tin halide perovskites [20] . Recently, the incorporation of large‐size organic cations such as n‐butylammonium (BA), and phenylethylammonium (PEA) have been proved to be an effective way to form the low‐dimensional tin halide perovskites with highly oriented crystal growth [23–27] . According to Wulff construction theory, the primary cause of orientation lies in the slower growth rate of perovskite crystals in a specific direction [28] .…”

Alkylamine screening and zinc doping of highly luminescent 2D tin-halide perovskites for LED lighting

“…It was obvious that longer alkylammonium chain could protect the [SnBr 6 ]octahedral luminescence centre more effectively, which in turns enhanced the stability of the 2D (RNH 3 ) 2 SnBr 4 perovskites. 29 Similar to other halide perovskites, 2D (RNH 3 ) 2 SnBr 4 perovskites can also vary its halide portion to tune the emission positions. 48 Various compositions of (C 8 H 17 NH 3 ) 2 SnX 4 perovskites were synthesized by simply tuning the dosage of HBr and HI proportion.…”

“…28 The length of the organic amine chain will affect the transport of carriers, thereby affecting the device performance of the 2D tinhalide perovskites. 29 30 In addition, we thoroughly discussed the effects of Asite organic cations' substitution on their structural, optical properties and stability. Spectral tunability of 2D tin hybrid perovskites by adjusting the Br/I halide ratio was also explored.…”

Exotic Structural and Optoelectronic Properties of Layered Halide Double Perovskite Polymorphs

“…One big challenge is the easy oxidation of Sn 2+ to Sn 4+ when exposed in air, another challenge is the difficulty to synthesize high‐quality thin films due to the rapid crystallization at room temperature. [ 46 ] Therefore, researchers have made great effort to improve the performance of Sn‐based perovskites, such as manipulating the crystal growth, [ 47,48 ] adding guanidinium thiocyanate, [ 5 ] antioxidant SnF 2 , [ 49 ] organic spacer cations with shorter alkyl chains, [ 50 ] alloying Pb 2+ or Ge 2+ , [ 51,52 ] lattice contraction, and octahedral tilting. [ 53 ] Further experimental efforts are called for to synthesize predicted Rb 4 SnSb 2 Br 12 LHDP in this work and use above possible strategies to improve its optoelectronic performance.…”