Vis ir 765

The macroscopic fluorescence lifetime imaging (MFLI) setup used in this work was identical to that described previously⁹ . Briefly, a pulsed laser emitting sub 100 ps pulses at 765 nm with an 80 MHz repetition rate (VIS-IR-765, Picoquant, USA), was coupled to a single-mode fiber and recollimated, expanded and homogenized with an engineered diffuser (ED1-S20-MD, Thorlabs) to form a homogeneous square illumination pattern on the sample plane. Excitation intensity was adjusted by inserting a neutral density filter before the diffuser. Fluorescence light emitted by the sample was collected with a NIR macroscopic lens attached to the SS3 detector, after rejection of the laser wavelength by a bandpass filter (FF01-893/209-25, Semrock, NY). The excitation and emission paths were enclosed in a black box preventing NIR light to escape and ambient room light to be detected by the instrument.
Instrument response functions (IRFs) were acquired with the same setup without the emission filter (and a stronger neutral density filter) using a sheet of white filter paper to scatter the laser light.

A frequency-doubled 382 nm picosecond pulsed laser (VisIR-765, PicoQuant), a photon counting avalanche photodiode (PDM series, Micro Photonics Devices), and spectrograph (shamrock 303i, Andor) were used for transient PL measurements. A variable-angle spectroscopic ellipsometer (J.A. Woollam M-2000FI) was used to measure the optical constants and thickness of QD thin films. The incident angle was varied from 55° to 75° in steps of 5°. The collected data were analyzed using Complete EASE software (J.A. Woollam Co. Inc.). A stylus profilometer was used to measure the thickness of the films. Femtosecond pump-probe absorption spectroscopy was performed with a femtosecond pulsed laser and transient absorption spectrometer (Helios, Ultrafast Systems). Ti:Sapphire regenerative amplifier (Spitfire, Spectra-Physics) and optical parametric amplifier (TOPAS, Spectra-Physics) were used as a laser light source. The pump beam was 400 nm in wavelength and had a fluence of 100 μJ cm⁻². Repetition rates of the probe and pump beam were 1000 Hz and 500 Hz, respectively.