Bhardwaj Aditya, Kundu Kaushik, Sasmal Ranjan, Acharyya Paribesh, Pradhan Jayita, Kalita Simanta, Agasti Sarit S, Biswas Kanishka
New Chemistry Unit and School of Advanced Materials Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) Jakkur P.O. Bangalore 560064 India
Chemistry and Physics of Materials Unit, JNCASR Jakkur P.O. Bangalore 560064 India.
Chem Sci. 2023 Jun 20;14(26):7161-7169. doi: 10.1039/d3sc02506c. eCollection 2023 Jul 5.
Lead (Pb)-free layered double perovskites (LDPs) with exciting optical properties and environmental stability have sparked attention in optoelectronics, but their high photoluminescence (PL) quantum yield and understanding of the PL blinking phenomenon at the single particle level are still elusive. Herein, we not only demonstrate a hot-injection route for the synthesis of two-dimensional (2D) ∼2-3 layer thick nanosheets (NSs) of LDP, CsCdBiCl (pristine), and its partially Mn-substituted analogue [, CsCdMnBiCl (Mn-substituted)], but also present a solvent-free mechanochemical synthesis of these samples as bulk powders. Bright and intense orange emission has been perceived for partially Mn-substituted 2D NSs with a relatively high PL quantum yield (PLQY) of ∼21%. The PL and lifetime measurements both at cryogenic (77 K) and room temperatures were employed to understand the de-excitation pathways of charge carriers. With the implementation of super-resolved fluorescence microscopy and time-resolved single particle tracking, we identified the occurrence of metastable non-radiative recombination channels in a single NS. In contrast to the rapid photo-bleaching that resulted in a PL blinking-like nature of the controlled pristine NS, the 2D NS of the Mn-substituted sample displayed negligible photo-bleaching with suppression of PL fluctuation under continuous illumination. The blinking-like nature in pristine NSs appeared due to a dynamic equilibrium flanked by the active and in-active states of metastable non-radiative channels. However, the partial substitution of Mn stabilized the in-active state of the non-radiative channels, which increased the PLQY and suppressed PL fluctuation and photo-bleaching events in Mn-substituted NSs.
具有令人兴奋的光学特性和环境稳定性的无铅层状双钙钛矿（LDPs）在光电子学领域引起了关注，但其高光致发光（PL）量子产率以及在单粒子水平上对PL闪烁现象的理解仍然难以捉摸。在此，我们不仅展示了一种热注入路线，用于合成二维（2D）约2 - 3层厚的LDP纳米片（NSs）、CsCdBiCl（原始的）及其部分Mn取代的类似物[, CsCdMnBiCl（Mn取代的）]，还介绍了这些样品作为块状粉末的无溶剂机械化学合成方法。对于部分Mn取代的2D NSs，观察到明亮且强烈的橙色发射，其PL量子产率（PLQY）相对较高，约为21%。采用低温（77 K）和室温下的PL和寿命测量来理解电荷载流子的去激发途径。通过实施超分辨荧光显微镜和时间分辨单粒子跟踪，我们确定了单个NS中存在亚稳态非辐射复合通道。与导致受控原始NS出现类似PL闪烁性质的快速光漂白不同，Mn取代样品的2D NS在连续光照下光漂白可忽略不计，且PL波动受到抑制。原始NSs中类似闪烁的性质是由于亚稳态非辐射通道的活跃和非活跃状态之间的动态平衡所致。然而，Mn的部分取代稳定了非辐射通道的非活跃状态，这提高了PLQY并抑制了Mn取代NSs中的PL波动和光漂白事件。
