Fig. 2
Characterizations of ligand attachment and transient absorption photophysics. a Fourier transform infrared (FT-IR) spectra of PbS QDs passivated by (i) MAPbI3 (ii) TG, and (iii) two types of ligands (mixed-QD sample). b 1H NMR spectra of quantum dot ligands in solution (red) and bound to PbS quantum dot surface (black). (i) Oleic acid and lead oleate-capped QDs in C6D6 benzene. (ii) TG and TG-capped QDs in d6-DMSO. (iii) MAI + PbI2 solution sample and MAI + PbI2-capped QDs in d7-DMF. For (ii) and (iii), signals between 0 and 2 ppm are from residual oleate bound to the QDs after the ligand exchange. Peaks from trace nondeuterated solvents are marked by asterisks. c Schematic representation of spectral diffusion. Dashed lines indicate the position of time traces for panels d–f relative to the peak maximum of the exciton bleach. d–f TA spectral time traces of bleaching signals for d TG-capped QDs, e MAPbI3-capped QDs, and f mixed-QD films. We track spectral diffusion by the point of crossover between the decay of high-energy wavelengths and the rise of lower energy wavelengths, encircled in black
