Defect Engineered g‑C₃N₄ for Efficient Visible Light Photocatalytic Hydrogen Production

Defect Engineered g‑C₃N₄ for Efficient Visible Light Photocatalytic Hydrogen Productio

Spatially-Resolved Ultrafast Optical Spectroscopy of Polymer-Grafted Residues on CVD Graphene

A recent report proved that polymer residues become grafted to graphene despite the efforts to clean the surface by thermal annealing [Lin, Y.-C., et al.<i> Nano Lett.</i> <b>2012</b>, <i>12</i>, 414]. Such residues inevitably originate from the photoresist (e.g., poly­(methyl methacrylate) (PMMA)) used for graphene transfer and device processing. Here, through spatially resolved transient absorption spectroscopy and transient photoluminescence spectroscopy, we investigate the effects of such polymer-grafted residues on the carrier dynamics of CVD graphene. The presence of these polymer-grafted residues is validated by both X-ray photoelectron spectroscopy and micro-Raman spectroscopy. Unlike the ultrafast nonradiative recombination at the pristine graphene, these regions exhibit distinct long-lived carrier dynamics that undergo radiative recombination, which is characteristic of the opening of the graphene bandgap. Understanding the influence of such defects on the carrier dynamics and relaxation pathways is key to modifying the optoelectronic properties of graphene-based devices

Iron Pyrite Thin Film Counter Electrodes for Dye-Sensitized Solar Cells: High Efficiency for Iodine and Cobalt Redox Electrolyte Cells

Iron pyrite has been the material of interest in the solar community due to its optical properties and abundance. However, the progress is marred due to the lack of control on the surface and intrinsic chemistry of pyrite. In this report, we show iron pyrite as an efficient counter electrode (CE) material alternative to the conventional Pt and poly(3,4-ethylenedioxythiophene (PEDOT) CEs in dye-sensitized solar cells (DSSCs). Pyrite film CEs prepared by spray pyrolysis are utilized in I₃^–/I^– and Co(III)/Co(II) electrolyte-mediated DSSCs. From cyclic voltammetry and impedance spectroscopy studies, the catalytic activity is found to be comparable with that of Pt and PEDOT in I₃^–/I^– and Co(III)/Co(II) electrolyte, respectively. With the I₃^–/I^– electrolyte, photoconversion efficiency is found to be 8.0% for the pyrite CE and 7.5% for Pt, whereas with Co(III)/Co(II) redox DSSCs, efficiency is found to be the same for both pyrite and PEDOT (6.3%). The excellent performance of the pyrite CE in both the systems makes it a distinctive choice among the various CE materials studied