Sn‐Based Perovskite Halides for Electronic Devices

Abstract

Because of its less toxicity and electronic structure analogous to that of lead, tin halide perovskite (THP) is currently one of the most favorable candidates as an active layer for optoelectronic and electric devices such as solar cells, photodiodes, and field‐effect transistors (FETs). Promising photovoltaics and FETs performances have been recently demonstrated because of their desirable electrical and optical properties. Nevertheless, THP's easy oxidation from Sn2+ to Sn4+, easy formation of tin vacancy, uncontrollable film morphology and crystallinity, and interface instability severely impede its widespread application. This review paper aims to provide a basic understanding of THP as a semiconductor by highlighting the physical structure, energy band structure, electrical properties, and doping mechanisms. Additionally, the key chemical instability issues of THPs are discussed, which are identified as the potential bottleneck for further device development. Based on the understanding of the THPs properties, the key recent progress of THP‐based solar cells and FETs is briefly discussed. To conclude, current challenges and perspective opportunities are highlighted.

Origins and Suppression of Sn(II)/Sn(IV) Oxidation in Tin Halide Perovskite Solar Cells

“…i) Multifunctional additives or solvents; Since Sn(II)/Sn(IV) oxidation could be influenced by multiple factors, including crystallization, hydrophobicity, ion migration in devices. [16,116,159] If additives or solvents can achieve two or more of these problems simultaneously, it will have a greater improvement on the performance and stability of TPSCs. ii) Understanding the antioxidant mechanism of additives or solvents.…”

“…[12][13][14] Thereinto, Sn, as a congener of Pb, not only has the same valence electron layer structure as Pb, but also has the most similar ionic radius (118 vs 119 pm) with Pb. [15,16] Besides, tin halide perovskites have a higher conduction band minimum (CBM) and valence band maximum (VBM) compared to that of lead analogs. [17,18] More importantly, tin perovskite has a band gap much closer to the ideal bandgap (1.3 eV) according to the Shockley-Quisser (S-Q) limit.…”

Strain Regulation and Photophysical Properties in Halide Perovskite

“…[51] The energy band is a quasicontinuous orbit formed by the orbital splitting and coupling of a large number of atoms, which is primarily influenced by the atomic outermost orbital coupling of the inorganic framework of halide perovskite. [52] A gradual shift in the valence band, caused by strain, has been observed, indicating that strain is an important factor influencing the band structure in halide perovskites. [53] Hao co-workers reported that the band structure of mixed-cation perovskite can be modulated through strain engineering via precursor aging.…”

Phase-Pure 2D/3D Tin-Based Perovskite Films for Solar Cells

“…Halide perovskite solar cells (PSCs), as a strong candidate for the next photovoltaic devices, deliver a certified power conversion efficiency (PCE) of over 26% for FAPbI 3 -based perovskites. − However, much attention has been paid to the toxicity of water-soluble Pb 2+ to the environment and humans . Environmentally friendly tin (Sn)-based perovskites are considered to be the most promising alternatives for advancing the development of the green perovskite photovoltaic industry, but there are still issues of Sn­(II) instability and poor device performance that need to be addressed. , Specifically, compared with Pb-based perovskites, the weaker Sn–I bonding makes the [SnI 6 ] 4– octahedral skeleton more fragile, leading to low formation energy of the Sn vacancy (V Sn ), high Sn-related defect density, and poor structural stability. − Therefore, the structural modulation strategy to stabilize the [SnI 6 ] 4– octahedral framework is considered as one of the key measures to improve the intrinsic and environmental stability of Sn-based perovskite films. , …”