Concurrent Energy- and Electron-Transfer Dynamics in Photoexcited Mn-Doped CsPbBr₃ Perovskite Nanoplatelet Architecture

Abstract

Mn-doped perovskites have already been widely explored in the context of interesting optical, electronic, and magnetic properties. Such fascinating traits showcased by them explain the huge augmentation in the device efficiency, directing their widespread application in the field of solar cells, energyharvesting sectors, and light-emitting diodes. However, the underlying photophysics governing the overall charge carrier dynamics in Mn-doped CsPbBr 3 nanoplatelets (NPLs) has never been discussed and therefore demands an in-depth investigation. Herein, fluorescence up-conversion and femtosecond transient absorption (TA) spectroscopy are employed for gaining a comprehensive understanding of the excited-state dynamics and the fundamental energy/charge-transfer processes for twodimensional CsPbBr 3 nanoplatelets (NPLs) and their Mn-doped counterparts. The up-conversion measurement clearly suggests the possibility of energy-transfer pathways in the Mn-doped CsPbBr 3 NPLs. Interestingly, strong indication of charge transfer (CT) in Mn-doped CsPbBr 3 NPLs was unambiguously established by an ultrafast TA approach. Our investigation clearly suggests that both the probable processes viz. the ultrafast energy and electron transfers noticeable in the Mn 2+ -doped CsPbBr 3 NPLs are utterly competitive and rapid owing to the highly confined nature of the two-dimensional NPLs. This extensive probing of concurrent charge/energy-transfer processes may pave help clarify unresolved anomalies in Mn-doped perovskites, which may prove advantageous for a wide range of practical applicability.

Energy vs Charge Transfer in Manganese-Doped Lead Halide Perovskites

“…The presence of Mn 3+ in perovskite samples was also invoked to rationalize the ferromagnetic coupling in MAPb 1– x Mn x I 3 , proposed to arise from Mn 2+ –I – –Mn 3+ motifs . Very recently, Babu et al revealed the formation of a transient charge-transfer state in Mn:CsPbBr 3 , suggesting that a spin-allowed charge-transfer process (concurrent to energy transfer) related to Mn 3+ formation is likely to occur …”

“… 48 Very recently, Babu et al revealed the formation of a transient charge-transfer state in Mn:CsPbBr 3 , suggesting that a spin-allowed charge-transfer process (concurrent to energy transfer) related to Mn 3+ formation is likely to occur. 49 …”

Defect-Interceded Cascading Energy Transfer and Underlying Charge Transfer in Europium-Doped CsPbCl3 Nanocrystals

“…Moreover, there is an onset of a new negative feature (bleach) in the lower-energy region around 412–430 nm for Eu-CsPbCl 3 . Such a bleach could be attributed to either a formation of an intermediate charge transfer band or the presence of defect states. , …”

Hexamethyldisilazane-assisted Mn2+ doping of perovskite nanocrystals under ambient conditions

“…As reported, the energy-transfer process in the doped system is related with the decrement of the excitonic decay in host emission with the increase in the emission of dopants, leading to a decrease in the PL decay lifetime of the excitonic emission in doped materials in comparison with that of undoped samples. 35,42 In our case, undoped CsPbCl 3 NCs are very difficult to collect in the absence of Mn 2+ ions, and thus we did not compare the lifetime between doped and undoped samples. The PL decay plots of representative Mn 2+ -doped CsPbCl 3 NCs monitored at 400 nm and 600 nm are provided in Fig.…”

“…The unique optical properties of Mn-doped LHP NCs and their promising applications led to worldwide research on various synthetic protocols. 38–44 Wang et al synthesized cube-like Mn 2+ -doped CsPbCl 3 NCs by using a hot-injection procedure. 45 Zheng and coworkers achieved very high Mn 2+ dopant substitution in Mn-doped 2-dimensional CsPbCl 3 nanoplatelets using a postsynthetic solvothermal procedure.…”