Fig. 4

Infrared pump photoluminescence (PL)-probe measurements of CH₃NH₃PbI₃. a Spectrally and temporally resolved PL counts measured with a streak camera (scalebar is in log₁₀ scale) without using the infrared pump. b Decay kinetics of the PL intensity acquired under various negative Δt values. c Decay kinetics of the PL intensity acquired under various positive Δt values, with (dashed lines) and without (solid lines) using the infrared pump. d Static, temperature-dependent, wavelength-integrated PL intensity of the CH₃NH₃PbI₃ film. e Time-integrated PL spectra acquired at 10 K and at 50 K, with Δt = 2000 ps. Relative change of the time-integrated PL spectra with various positive delay times measured at 10 K in (f), and measured at 50 K in (g, h). An on-resonance (3120 cm⁻¹) infrared pump was used in (e, f, g); an off-resonance (2200 cm⁻¹) infrared pump was used in (h). Fluence of the infrared pump was fixed at 3.8 mJ cm⁻² in these measurements. Legend in (h) also applies to (f, g)