Self-Trapped Excitons Mediated Energy Transfer to Sm³⁺ in Cs₂AgIn_(1–x)Sm_xCl₆:Bi Double Perovskite Nanocrystals

Abstract

Lanthanide ions (Ln3+) are well-known dopants for controlling the optoelectronic properties of double perovskites (DPs). However, the excitation energy of Ln3+-doped Cs2AgInCl6 being too high (∼250–290 nm) limits its direct excitation by commercial UV light-emitting diodes (≥365 nm). To overcome this challenge, we employed Bi3+ as a sensitizer to induce the emission of Sm3+ at much lower excitation energy in Sm3+–Bi3+ codoped Cs2AgInCl6 DP nanocrystals (NCs). Spectral analysis shows that a trace amount of Bi3+ (∼1%) doping provides dual emission of self-trapped excitons (STEs) and characteristic emissions of Sm3+ assigned to 4G5/2 to 6H J (J = 5/2, 7/2, 9/2, and 11/2) transitions with 368 nm excitation energy. Transient absorption spectroscopic results revealed the existence of nonradiative energy transfer from STE states. Subsequently, we propose a mechanism to explain the formation of energy-transfer channels from STEs to excited states of Sm3+. Our study demonstrates that Bi3+ can efficiently sensitize Sm3+ to modify the optical properties of lead-free DP NCs to expand their luminescence application.

Elucidating the Mn2+ Dopant Sites in Two-Dimensional Na–In Halide Perovskite

“…Through the controllable doping of certain homo or heterovalent cations, new emission features can be added to these materials. The choices for the optically active dopant, for the wide band gap host semiconductors, have been mainly transition metals, such as Mn 2+ . , Extensive research has been conducted on the incorporation and effects of Mn 2+ , including the chemical and structural changes, spatial distribution of dopant, and energy transfer phenomenon of host to dopant resulting in a signature orange-red emission. − The sensitization mechanism of dopant from host is not yet clear; it could be from band edge to dopant ion or from the defect mediated energy transfer. − …”

Lanthanide Doping into All-Inorganic Heterometallic Halide Layered Double Perovskite Nanocrystals for Multimodal Visible and Near-Infrared Emission

“…These include the ability to adjust multimodal photoluminescence (PL) profiles across both visible and near-infrared (NIR) spectral ranges due to the presence of rich energy levels, − enhanced light conversion efficiency with potential quantum cutting effects, , and induction of a robust magnetic moment with both orbital and spin contributions originating from unpaired f-electrons. , Nevertheless, Ln 3+ ions typically display a low absorption extinction coefficient due to their parity-forbidden f – f transitions. − In addition, the facile coupling between lattice vibrations and NIR transitions of neighboring Ln dopants can lead to reduced PL quantum yield (QY) through self-quenching. − To date, successful doping of Ln 3+ into lead-free perovskite NC systems has been very limited. Reported examples include the incorporation of Ln 3+ ions (such as Yb 3+ , Er 3+ , and Tb 3+ ) within Cs 2 M­(I)­M­(III)­Cl 6 (M­(I): Na + , Ag + ; M­(III): Bi 3+ , In 3+ ) double perovskite NCs, resulting in enhanced optical properties in the NIR range. , Co-doping Ln 3+ (e.g., Tb 3+ , Er 3+ , Sm 3+ , Nd 3+ ) with main group trivalent metal cations (e.g., Bi 3+ , Sb 3+ ) in Cs 2 AgInCl 6 double perovskite NCs has also been demonstrated. − Compared to double perovskites, LDPs possess a unique 2D layered “sandwiched” crystal structure that remains largely unexplored with regard to the Ln 3+ doping positions and energy transfer mechanisms . Despite few trials of doping Ln 3+ ions into bulk-scale LDPs, − the incorporation of Ln 3+ dopants in nanoscale LDP materials, enabling multimodal visible/NIR emissions, has yet to be presented.…”

Extending the absorption of Cs2AgBiCl6 double perovskite to the near infra-red region by copper doping

“…[20][21][22][23][24][25][26][27][28] Lead-free double perovskite semiconductors have attracted attention due to their high thermal and structural stability under ambient conditions, and highly tunable band gap. 25,26,[29][30][31][32][33] The general formula for halide double perovskites is A 2 M I M III X 6 , where A and M I are monovalent cations, M III is a trivalent cation and X is a halide anion. The silver-and bismuth-based Cs 2 Ag-BiCl 6 is a well-known lead-free halide double perovskite, which is highly resistive against thermal and other environmental factors and hence presents great stability.…”