Liu Maning, Matta Sri Kasi, Said Tarek Al, Liu Jiatu, Matuhina Anastasia, Al-Anesi Basheer, Ali-Löytty Harri, Lahtonen Kimmo, Russo Slavy P, Vivo Paola
Centre for Analysis and Synthesis, Department of Chemistry, Lund University, P.O. Box 124, Lund, 22100, Sweden.
Wallenberg Initiative Materials Science for Sustainability, Department of Chemistry, Lund University, Lund, 22100, Sweden.
Small. 2024 Oct;20(40):e2401051. doi: 10.1002/smll.202401051. Epub 2024 May 29.
Lead-free layered double perovskite nanocrystals (NCs), i.e., CsM(II)M(III)Cl, have recently attracted increasing attention for potential optoelectronic applications due to their low toxicity, direct bandgap nature, and high structural stability. However, the low photoluminescence quantum yield (PLQY, <1%) or even no observed emissions at room temperature have severely blocked the further development of this type of lead-free halide perovskites. Herein, two new layered perovskites, CsCoInCl (CCoI) and CsZnInCl (CZnI), are successfully synthesized at the nanoscale based on previously reported CsCuInCl (CCuI) NCs, by tuning the M(II) site with different transition metal ions for lattice tailoring. Benefiting from the formation of more self-trapped excitons (STEs) in the distorted lattices, CCoI and CZnI NCs exhibit significantly strengthened STE emissions toward white light compared to the case of almost non-emissive CCuI NCs, by achieving PLQYs of 4.3% and 11.4% respectively. The theoretical and experimental results hint that CCoI and CZnI NCs possess much lower lattice deformation energies than that of reference CCuI NCs, which are favorable for the recombination of as-formed STEs in a radiative way. This work proposes an effective strategy of lattice engineering to boost the photoluminescent properties of lead-free layered double perovskites for their future warm white light-emitting applications.
无铅层状双钙钛矿纳米晶体（NCs），即CsM(II)M(III)Cl，由于其低毒性、直接带隙特性和高结构稳定性，最近在潜在的光电子应用中受到越来越多的关注。然而，低光致发光量子产率（PLQY，<1%）甚至在室温下未观察到发射，严重阻碍了这类无铅卤化物钙钛矿的进一步发展。在此，基于先前报道的CsCuInCl（CCuI）NCs，通过用不同的过渡金属离子调整M(II)位点进行晶格剪裁，成功地在纳米尺度上合成了两种新的层状钙钛矿CsCoInCl（CCoI）和CsZnInCl（CZnI）。受益于在扭曲晶格中形成更多的自陷激子（STE），与几乎无发射的CCuI NCs相比，CCoI和CZnI NCs分别实现了4.3%和11.4%的PLQY，朝着白光方向表现出显著增强的STE发射。理论和实验结果表明，CCoI和CZnI NCs的晶格变形能比参考CCuI NCs低得多，这有利于形成的STE以辐射方式复合。这项工作提出了一种有效的晶格工程策略，以提高无铅层状双钙钛矿的光致发光性能，用于其未来的暖白光发射应用。
