Spinodal Decomposition During Anion Exchange in Colloidal Mn2+-Doped CsPbX3 (X = Cl, Br) Perovskite Nanocrystals,Chemistry of Materials

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Spinodal Decomposition During Anion Exchange in Colloidal Mn2+-Doped CsPbX3 (X = Cl, Br) Perovskite Nanocrystals
Chemistry of Materials ( IF 7.2 ) Pub Date : 2019-09-06 , DOI: 10.1021/acs.chemmater.9b02646
Michael C. De Siena ₁ , David E. Sommer ₂ , Sidney E. Creutz ₁ , Scott T. Dunham ₃ , Daniel R. Gamelin ₁

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Manganese(II)-doped cesium–lead–chloride (Mn²⁺:CsPbCl₃) perovskite nanocrystals have recently been developed as promising luminescent materials and attractive candidates for white-light generation. One approach to tuning the luminescence of these materials has involved anion exchange to incorporate Br^–, but the effects of anion exchange on Mn²⁺ speciation in doped metal-halide perovskites is not well understood at a microscopic level. Here, we use a combination of X-band electron paramagnetic resonance (EPR) and photoluminescence spectroscopies to monitor the Mn²⁺ dopants in Mn²⁺:CsPbCl₃ nanocrystals during Cl^– → Br^– anion exchange. Analytical measurements show that the nanocrystals retain their Mn²⁺ over the course of Cl^– → Br^– anion exchange and they continue to show strong Mn²⁺d–d luminescence but, surprisingly, the Mn²⁺ EPR intensities all but vanish. Further results suggest that Mn²⁺ ions migrate during anion exchange to form clusters that are still luminescent but show no EPR signal due to antiferromagnetic superexchange coupling. Monte Carlo simulation and analysis of the Mn²⁺:CsPb(Cl_1–xBr_x)₃ lattice at various halide compositions (x) bolsters this interpretation by indicating a propensity for Mn²⁺–Cl^– units to cluster as the Br^– content increases, increasing the probability of the nearest-neighbor Mn²⁺–Mn²⁺ interactions. The driving force for this clustering is retention of the stronger Mn–Cl bonds compared to Mn–Br bonds. In addition, modeling predicts spinodal decomposition to form Mn²⁺-enriched domains even at the end point compositions of x = 0 and 1, with Mn²⁺ ordering in next-nearest-neighbor positions driven by Coulomb interactions and lattice-strain minimization. These results have important implications for both fundamental studies and applications of doped and alloyed metal-halide perovskites.

中文翻译：

掺杂Mn2 +的CsPbX3（X = Cl，Br）钙钛矿纳米晶体中阴离子交换过程中的旋节分解。

锰（II）掺杂的铯-铅-氯化物（Mn ²⁺：CsPbCl ₃）钙钛矿纳米晶体最近已被开发为有前途的发光材料和诱人的白光产生材料。调谐这些材料的发光的一种方法已经涉及阴离子交换掺入溴^-，但在锰的阴离子交换的影响²⁺在掺杂金属卤化物的钙钛矿形态没有很好地在微观水平上理解。在这里，我们结合X波段电子顺磁共振（EPR）和光致发光光谱法，在Cl ^– →Br ^–期间监测Mn ²⁺：CsPbCl ₃纳米晶体中的Mn ²⁺掺杂剂。阴离子交换。分析测量结果表明，纳米晶体在Cl ^– →Br ^–阴离子交换过程中保留了Mn ²⁺，并且它们继续显示强Mn ²⁺d–d发光，但令人惊讶的是，Mn ²⁺ EPR强度几乎消失了。进一步的结果表明，Mn ²⁺离子在阴离子交换过程中迁移形成簇，这些簇仍然发光，但由于反铁磁超交换耦合而没有显示EPR信号。蒙特卡洛模拟和锰的分析²⁺：CSPB（CL _1-_X溴_X）₃晶格在各种卤化物组合物（X）通过指示的Mn的倾向支持了这种解释²⁺ -Cl ^-单位簇作为溴^-含量的增加，增加了最近邻Mn的概率²⁺ -Mn ²⁺相互作用。与Mn-Br键相比，该簇的驱动力是保留了较强的Mn-Cl键。此外，建模预测旋节分解而形成的Mn ²⁺即使在结束点的组合物富集的结构域X = 0和1，与锰²⁺在库仑相互作用和晶格应变最小化的驱动下，在最近的邻居位置中排列。这些结果对掺杂和合金化金属卤化物钙钛矿的基础研究和应用都具有重要意义。

更新日期：2019-09-06

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