Mechanism for the Extremely Efficient Sensitization of Yb³⁺Luminescence in CsPbCl₃ Nanocrystals

Abstract

Rare earth ion (RE3+)-doped inorganic CsPbX3 (X = Cl or Cl/Br) nanocrystals have been presented as promising materials for applications in solar-energy-conversion technology. An extremely efficient sensitization of Yb3+ luminescence in CsPbCl3 nanoparticles (NCs) was very recently demonstrated where quantum cutting is responsible for the performance of photoluminescence quantum yields over 100% (Nano Letters2018183792). In the present work, based on the cubic phase of inorganic perovskite, we seek to obtain atom-level insight into the basic mechanisms behind these observations in order to boost the further development of RE3+-doped CsPbX3 NCs for optoelectronics. In our calculations of cubic crystal structure, we do not find any energy level formed in the middle of the band gap, which disfavors a mechanism of stepwise energy transfer from the perovskite host to two Yb3+ ions. Our work indicates that the configuration with “right-angle” Yb3+-VPb-Yb3+ couple is most likely to form in Yb3+-doped CsPbCl3. Associated with this “right-angle” couple, the “right-angle” Pb atom with trapped excited states would localize the photogenerated electrons and act as the energy donor in a quantum cutting process, which achieves simultaneous sensitization of two neighboring Yb3+ ions.

Lanthanide doping in metal halide perovskite nanocrystals: spectral shifting, quantum cutting and optoelectronic applications

“…It was suggested that this defect forms a shallow state below the conduction band minimum, facilitating picosecond nonradiative energy transfer from the photoexcited host NC to two Yb 3+ ions simultaneously, yielding quantum cutting 22 . Later, theoretical studies extended the mechanistic insight 36 . They suggested that the two Yb 3+ dopants are excited in a concerted manner through nonradiative energy transfer from the PbCl 6 octahedra closest to the two Yb 3+ dopants (see Fig.…”

“…They suggested that the two Yb 3+ dopants are excited in a concerted manner through nonradiative energy transfer from the PbCl 6 octahedra closest to the two Yb 3+ dopants (see Fig. 3c) 36 .…”

Switching on Near-Infrared Light in Lanthanide-doped CsPbCl3 Perovskite Nanocrystals.pdf

“…[14][15][16][17][18][19][20][21] Nonetheless, the upper limit of the emission wavelength still remains below 1.0 μm, which greatly restricts the particularly interesting applications of these materials in optoelectronic and photonic devices working in the NIR such as telecommunication, light-emitting diodes, and lasers. [22][23][24] Unlike Yb 3+ -doped CsPbCl3, which exhibits an extremely intense Yb 3+ NIR emission at ~1.0 μm through a quantumcutting effect, [17,19,25] other NIR luminescent lanthanide ions (Ln 3+ ), such as Er 3+ , Nd 3+ and Ho 3+ unexpectedly show negligible emission. This anomalous phenomenon is likely related to the relatively high redox potential of the Yb 3+ /Yb 2+ pair which allows for a transient internal redox mechanism within the CsPbCl3 matrix releasing enough energy to excite two Yb 3+ ions.…”

Switching to the brighter lane: pathways to boost the absorption of lanthanide-doped nanoparticles

“…In lead-based systems, doping with Ln 3+ proceeds through the substitution of three Pb 2+ for every two incorporated lanthanides. 96,118 To maintain a charge balance, a Pb 2+ vacancy (VPb) is also introduced. The most energetically favourable configuration of the resulting defect complex (Ln 3+ -VPb-Ln 3+ ) is shown in (Figure 5E).…”

“…In a following study, Li et al modelled this quantum cutting phenomenon and explained it in light of a higher density of states at the CB edge featured by the Pb 2+ sitting close to the Yb 3+ ions; this favours strong localized absorption and prompt transfer of the energy to the two nearby Yb 3+ . 118 Ln 3+ -doped lead-based perovskite SNCs were also used for preparing with-light emitting diodes, wherein blueemitting GaN chips where coated with polymeric dispersions of, e.g., CsPbCl3:Ce 3+ ,Eu 3+121 or…”