DOI: 10.5061/dryad.6wwpzgn2x
title: Hot carrier extraction from 2D semiconductor photoelectrodes

description: Hot carrier-based energy conversion systems could double the efficiency of
 conventional solar energy technology or drive photochemical reactions that
 would not be possible using fully thermalized, “cool” carriers, but
 current strategies require expensive multi-junction architectures. Using
 an unprecedented combination of photoelectrochemical and in situ transient
 absorption spectroscopy measurements, we demonstrate ultrafast (&lt;50
 fs) hot exciton and free carrier extraction under applied bias in a
 proof-of-concept photoelectrochemical solar cell made from earth-abundant
 and potentially inexpensive monolayer (ML) MoS2. Our approach facilitates
 ultrathin 7 Å charge transport distances over 1 cm2 areas by
 intimately coupling ML-MoS2 to an electron-selective solid contact and a
 hole-selective electrolyte contact. Our theoretical investigations of the
 spatial distribution of exciton states suggest greater electronic coupling
 between hot exciton states located on peripheral S atoms and neighboring
 contacts likely facilitates ultrafast charge transfer. Our work delineates
 future 2D semiconductor design strategies for practical implementation in
 ultrathin photovoltaic and solar fuels applications.
description: Transient absorption data were collected with at 390 nm pump
 pulse (50 fs) and broadband white light probe pulse. The delay time
 between the pump and probe was scanned from -1.2 ps to 201 ps. Spectra
 were imported into Matlab and plotted in contour plots as a function of
 delay time and wavelength. The spectra are given here in Matlab workspace
 format (.mat). To fit each exciton peak, the spectrum at each time delay
 was segmented into the A-exciton region (630 nm – 685 nm), B-exciton
 region (580 nm – 630 nm), and C-exciton region (413 nm – 460 nm). Each
 region was fit with a convolution of a gaussian and line to fit the
 exciton peak and background signal, respectively. The amplitudes of the
 gaussian fits were plotted as a function of delay time for each exciton.
 These plots were fit as described in detail in the Supplementary
 Information. All raw spectral data and processed data are saved in a
 Matlab workspace and uploaded here. Potential-dependent
 absorbance measurements were taken by recording transmission microscope
 images of the sample while scanning the monochromatic light source from
 375 nm to 700 nm. The image files were analyzed using Matlab script to
 select and track pixel trajectories, then sync these trajectories with
 each wavelength scanned with the monochromatic light source via the data
 acquisition card (DAQ). The absorbance was calculated using the intensity
 of chosen sample pixels and intensity of chosen background pixels at each
 wavelength. All data extracted from the images and the DAQ card are saved
 in a Matlab workspace and uploaded here.
description: The data files are Matlab Data workspace files (.mat). Scripts
 used to process the transient absorption data and the potential-dependent
 absorbance are Matlab files (.m). Codes used to do BSE-GW calculations are
 python scripts (.py).