This paper describes an increase in the yield of collisionally gated photoinduced electron transfer (electron transfer events per collision) from oleate-capped PbS quantum dots (QDs) to benzoquinone (BQ) with increasing temperature (from 0 to 50 °C), due to increased permeability of the oleate adlayer of the QDs to BQ. The same changes in intermolecular structure of the adlayer that increase its permeability to BQ also increase its permeability to the solvent, toluene, resulting in a decrease in viscous drag and an apparent increase in the diffusion coefficient of the QDs, as measured by diffusion-ordered spectroscopy (DOSY) NMR. Comparison of NMR and transient absorption spectra of QDs capped with flexible oleate with those capped with rigid methylthiolate provides evidence that the temperature dependence of the permeability of the oleate ligand shell is due to formation of transient gaps in the adlayer through conformational fluctuations of the ligands.

The dynamics of electronic transitions in solid-state materials are closely linked to microscopic morphology, but it is challenging to simultaneously characterize their spectral and temporal response with high spatial resolution. We present a time-resolved nonlinear microscopy system using white-light supercontinuum pulses as a broadband light source. This system is capable of correlating nanometer scale sample morphology determined from atomic force topography measurements with broadband transient absorption hyperspectral images and ultrafast 2D white-light spectra, all with a spatial resolution of ≤1 μm. The experimental apparatus is described with a focus on the dispersion management strategies necessary to minimize the duration of optical pulses when implementing an AOM based pulse-shaping system covering a broad-spectral range in the VIS/NIR. Experiments on TIPS–pentacene organic semiconductor microcrystals are used to demonstrate the unique capabilities of this technique.

Defects in molecular crystals, created by nonequilibrium crystal packing, can have significant influence over the energetics and dynamics of singlet fission. Though normally thought of as detrimental to the performance of organic semiconductors, in principle, defects could have crystal packings with better energetics and couplings for singlet fission than equilibrium crystal packing structures. Using two-dimensional electronic microscopy and X-ray diffraction, we monitor the population of nonequilibrium slip-stacked geometries in microcrystals of TIPS-pentacene before and after thermal annealing. We find that the presence of these slip-stacked structures enhances the singlet fission yield, as measured by triplet excited state absorption. The slip-stacked geometry matches no known polymorph of TIPS-pentacene, according to X-ray diffraction but indicates that slip-stacked molecules are present as tiny crystalline domains within the larger microcrystal. The data presented here provide evidence that slip-stacked geometries, present as defects in larger TIPS-pentacene microcrystals, enhance singlet fission yields.

We report on a new broadband, ultrafast twodimensional white-light (2DWL) spectrometer that utilizes a supercontinuum pump and a supercontinuum probe generated with a ytterbium fiber oscillator and an all-normal dispersion photonic crystal fiber (ANDi PCF). We demonstrate compression of the supercontinuum to sub-20 fs and the ability to collect high quality 2D spectra on films of single-walled carbon nanotubes. Two spectrometer designs are investigated. Supercontinuum from ANDi PCF provides a means to generate broadband pulse sequences for multidimensional spectroscopy without the need for an optical parametric amplifier.

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