Fig. 1

Schematic diagram of solid echo pulse sequence[16]

Fig. 2

(a) DSC curves and (b) powder XRD patterns of MA1-xDMAxPbBr3 (x=0 and 0.4)

Fig. 3

Variable-temperature solid-state 2H NMR spectra of (a) MA0.6(d3)DMA0.4PbBr3 and (b) MA0.6DMA0.4(d6)PbBr3

Fig. 4

Motion models of MA and the corresponding simulated 2H spectra in MAPbBr3 with different phase structures[22]. (a) MA in static state and the simulated spectrum; (b) The methyl group of MA under intrinsic rotation along C-N bond and the simulated spectrum. Simulation condition: the angle between C-D bond and C-N axis θ = 70?, and the rotation rate reaches fast limit; (c) MA undergoes intrinsic methyl rotation and meanwhile rotates around Rc axis. Simulation condition: the inclined angle between C-N bond and Rc axis is θ = 54.7?, and the rotation rates (Ω) along the Rc axis are 30 kHz and 60 kHz, respectively; (d) MA undergoes isotropic tumbling and the motion rate reaches fast limit

Fig. 5

(a) The motion model of DMA cation and (b) the simulated 2H NMR spectrum of CD3 in DMA under static state

Fig. 6

(a) The motion model of DMA cation and (b) the simulated 2H NMR spectrum of CD3 in DMA when methyl groups undergo the intrinsic rotation along C-N bond. Simulation condition: the angle between C-D bond and C-N axis θ = 70?, and the rotation rate reaches fast limit

Fig. 7

(a) The double rotation model of DMA cation: the methyl groups undergo the intrinsic rotation along C-N bond and meanwhile DMA rotates along Rc axis, which is the in-plane bisector of the C-N-C angle; (b) The simulated 2H NMR spectrum of CD3 in DMA using the model in (a). Simulation condition: the angle between Rc and C-N axis θ = 54.7?, and the rotation rate reaches fast limit; (c) The simulated 2H NMR spectra of CD3 in DMA using the model in (a). Simulation condition: the angle between Rc and C-N axis θ = 54.7?, and the rotation rates (Ω) range from 40 kHz to 1 600 kHz

Fig. 8

(a) The Gaussian distribution of the inclined angle, θ, in the double rotation model of DMA cation. The standard deviation is σ，θ0 is the initial value of θ; (b) The simulated 2H NMR spectra of CD3 in DMA using the model in (a). Spectral simulation conditions: θ0 = 54.7?, the rotation rate along the rotation axis Rc is 100 kHz; The 2σ values change from 0? to 20?

Fig. 9

(a) Static solid state 2H NMR spectra of MA0.6(d3)DMA0.4PbBr3. The experimental temperatures range from 150 K to 300 K; (b) The simulated 2H NMR spectra of MA. Spectral simulation conditions: MA undergoes the double rotation. The angle between Rc and C-N axis is θ = 54.7?, and the rotation rates (Ω) range from 32 kHz to fast limit

Fig. 10

(a) Static solid state 2H NMR spectra of MA0.6DMA0.4(d6)PbBr3. The experimental temperatures range from 150 K to 300 K; (b) The simulated 2H NMR spectra of DMA. Spectral simulation conditions: DMA undergoes the double rotation. The angle between Rc and C-N axis is θ = 54.7?, and the rotation rates (Ω) range from 100 kHz to fast limit

Fig. 11

Linear fitting for the plot of lnΩ against 1000/T. The rates, Ω, of MA and DMA cations are related to the rotation along Rc axis, which are obtained from the simulation. The temperatures range from 150 K to 190 K