Two-dimensional (2D) perovskites with n-alkylammonium cations often undergo a solid–solid phase transition upon changes in pressure or temperature, during which the organic cations undergo an order-to-disorder chain-melting transition. Here, we show that blending halides and organic cations of varying lengths decreases the phase transition temperature of Cu- and Mn-based 2D perovskites. The magnitude of this decrease depends on the relative lengths of the two n-alkylammonium cations. For instance, blending n-decylammonium (DA) with n-undecylammonium (UDA) results in a 5 °C decrease in the phase transition temperature compared to pure DA₂CuBr₄. In contrast, blending DA with n-dodecylammonium (DDA) causes a 25 °C decrease. Furthermore, we found that blending Cu²⁺ and Mn²⁺ has a minimal effect on the phase transition temperature due to similar lattice spacing between the inorganic layers in DA₂CuCl₄ and DA₂MnCl₄. Our study suggests new design principles for tuning structural phase transitions in 2D perovskites through alloying halides, organic cations, and metal cations.

中文翻译：

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二维钙钛矿有机层中的链熔温度降低


具有 n-烷基铵阳离子的二维 （2D） 钙钛矿通常在压力或温度变化时发生固-固相转变，在此期间有机阳离子经历有序到无序的链熔化转变。在这里，我们表明，混合不同长度的卤化物和有机阳离子会降低铜基和锰基 2D 钙钛矿的相变温度。这种减少的幅度取决于两种 n-烷基铵阳离子的相对长度。例如，与纯 DA₂CuBr₄ 相比，将正十一铵 （DA） 与正十一铵 （UDA） 混合会导致相变温度降低 5 °C。相比之下，将 DA 与 n-十二铵 （DDA） 混合会导致 25 °C 的降温。此外，我们发现混合 Cu²⁺ 和 Mn²⁺ 对相变温度的影响很小，因为 DA₂CuCl₄ 和 DA₂MnCl₄ 中无机层之间的晶格间距相似。我们的研究提出了新的设计原则，通过合金卤化物、有机阳离子和金属阳离子来调节 2D 钙钛矿中的结构相变。