![]() Bright triplet excitons in caesium lead halide perovskites. c TRFE signal for two circular polarizations of pump: σ + (red) and σ − (blue). Metal halide perovskites (MHPs) with general formula of ABX 3. Bright Triplet Excitons in Caesium Lead Halide. Arrow at delay of − T D = −1.32 ns marks the position of the amplitude relaxation measurement. PDF The recent emergence of metal halide perovskites as triplet sensitizers has generated new possibilities in optoelectronics. Inset shows TRFE for negative time delays in the two-pump protocol. Exponential fit gives decay time of the burst amplitude τ = 0.5 s, corresponding to the changeover time between the distributions, after blocking the second pump. b Relaxation dynamics of the burst amplitude A FE(− T D) measured by switching from two-pump to one-pump protocol. Note, that the stronger hole-nuclear interaction compared to the electron-nuclear one is specific for lead halide perovskite semiconductors 35, due to their “inverted” band structure in comparison to semiconductors like GaAs or CdTe.Ī Schematic representation of the distribution ∣ S z ∣ of spin precession modes within the g-factor spread (green Gaussian) in the two-pump compared to the one-pump protocol. From its value and the strong changes of ω L in presence of polarized nuclei we conclude that the signal is dominated by resident holes with g h = +1.20 (see Supplementary Notes 1 and 2). 2c, see details below) indicate that the g-factor has a positive sign. General theoretical arguments and the experiments on dynamic nuclear polarization (Fig. Abstract: The lowest-energy exciton state in caesium lead halide perovskite nanocrystals is shown to be a bright triplet state, contrary to expectations that lowest-energy excitons should always be dark. Lead halide perovskites have emerged as promising new semiconductor materials for high-efficiency photovoltaics. In the latter case, an offset equal to the electron–hole exchange would be expected. In addition to this, lead-halide perovskite nanocrystals remain bright emitters when the size of the nanocrystal imposes only weak quantum confinement. S4a), which is a strong argument in favor of the presence of resident carriers in the NCs rather than of carriers bound in an exciton 23. ω L has no offset at zero magnetic field (Fig. This allows us to evaluate the g-factor of ∣ g ∣ = 1.20. The spin physics of perovskite nanocrystals with confined electrons or holes is attracting increasing attention, both for fundamental studies and spintronic applications. ![]()
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