Fig. 2: Anisotropic relaxation and structure dynamics evolution of MAPbBr3.
a Schematic illustration of the polarization-resolved transient transmission measurement performed on the differently oriented MAPbBr3 crystal wafers. b The pump fluence-dependent transient transmittance changes |ΔT/T0| of the (001) wafer. The results are fitted by the biexponential decay function. The fitting equation is: |ΔT/T0 | t = A1e(-t/τ1)+A2e(-t/τ2) + A0. A1 and A2 correspond to the respective phonon-mediated relaxation channels; A0 represents the thermal diffusion. c The transient transmission peak value (ΔT/T0 | t=1.5) as a function of pump fluence. d The decay lifetimes as a function of pump fluence. e Schematic of the photoexcited carrier relaxation dynamics: (Stage I) electron–LO–phonon scattering (Fröhlich interaction); (Stage II) optical phonon decay to acoustic phonons; (Stage III) acoustic phonons decay and propagation. f–h The pseudocolor polarization-resolved transient transmission plots of the (100), (110) and (111) wafers, respectively. i–k The probe polarization on the peak value (ΔT/T0 | t=1.5) of differently oriented wafers. l–q The probe polarization on the decay lifetimes of differently oriented wafers. r Schematic of the structural vibrations accompanying the anisotropic carrier relaxation in MAPbBr3.
