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Metal Halide Perovskites (MHP) have attracted significant research interest due to their unique properties and potential applications in photovoltaics, optoelectronics, and catalysis. Due to the huge concerns about lead toxicity in traditional metal halide perovskite, Lead-free perovskites have gained significant attention in recent years as alternative materials that can offer similar or better performance. Sn has been extensively investigated as an alternative to Pb in perovskite materials because they have a similar crystal structure as Pb-based MHP and can exhibit desirable optoelectronic properties, including high absorption coefficients and long carrier lifetimes. However, Sn perovskites also face challenges that must be addressed for widespread implementation. One of the major issues is their lower stability compared to lead perovskites, especially when exposed to moisture or elevated temperatures due to the prone of Sn(II) to oxidize to Sn(IV). Tin perovskites tend to undergo phase transitions and degrade more easily, decreasing device performance over time.
Researchers are actively working on improving the stability and performance of tin perovskites through various synthetic strategies. These include compositional engineering, dimensionality, interface modifications, encapsulation techniques, and device architecture optimization. Among them, low-dimensional perovskite structures, particularly layered structures, often exhibit improved stability compared to their bulk counterparts. The reduced dimensionality can mitigate ion migration and phase instability issues, leading to enhanced device performance and longevity. In low-dimensional materials, the confinement of charge carriers can lead to quantum confinement effects. These effects result in unique electronic properties, such as increased exciton binding energy and efficient charge transport. This can be advantageous for achieving high-efficiency solar cells and other optoelectronic devices.
Our research group has conducted investigations into the synthesis of low-dimensional Sn halide perovskites from micro and nanocrystals using different chemical routes, from traditional wet chemistry to in situ synthesis. We explore the versatility of the hot-injection approach for the dimensionality control of tin (II) halide perovskites microcrystals using 2-thiophene ethylene amine (TEA) as a bulky cation. TEA-Sn molar ratio plays an essential role in the formation and stabilization of 0D Sn-based MHP with excellent photoluminescence quantum yields (PLQY > 70%). Moreover, we report on a novel approach for the in-situ synthesis of 2D and 0D TEA₂SnX₄nanocrystals embedded in a nanocomposite with excellent stability. This technique is low-cost and low-energy demanding, allowing modifications to precursor solutions for compatibility with commercial printing techniques, ultimately contributing to the success of MHP. The in-situ synthesis approach also offers a low-carbon footprint synthetic route, making it more sustainable than traditional wet chemistry. We demonstrated how adjusting crystal growth from macro to nanoscale, using innovative synthetic routes ¹ and surface treatments, can alter optoelectrical response through fundamental changes in surface and bulk structure and composition.

1. Low-demanding in situ crystallization method for tunable and stable perovskite nanoparticle thin films
J. Noguera-Gómez, I. Fernández-Guillen, P. F. Betancur, V. S. Chirvony, P. P. Boix, R. Abargues
Matter. 2022, 5, 3541-3552
https://doi.org/10.1016/j.matt.2022.07.017

Rafael Abargues

Appearances