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Two-dimensional metal halide perovskite nanocrystals are attractive for their blue-shifted absorption relative to their 3D counterparts, narrow emission line widths, high absorption cross sections,...

Fully fluorinated perfluorocarbon ligands are shown to modify the energetics and dielectric environment of quantum dots (QDs), resulting in a large hypsochromic shift in the optical gap. The original oleic acid (OA) ligands on PbS QDs can be completely replaced with thiolate and carboxylate-based perfluorocarbons, e.g., -SCF3 and CF3(CF2)14COOH (pFA), respectively. Ultraviolet photoelectron spectroscopy indicates that the work function varies by >1.3 eV depending on the electronegativity of the surface ligand, while cyclic voltammetry shows that an OA:pFA ratio of ∼2:1 increases the oxidation potential by 0.18 eV in solution. The diminished reduction potential of the conduction band is confirmed by photoinduced electron transfer experiments. The short thiolate ligands, -SCF3 and -SCH3, enhance the electron-donating ability of PbS QDs up to 7-fold because of an increase in the permeability of the ligand shell. This work shows that electron-withdrawing halogens like fluorine and chlorine can control the ban...

A critically important question that must be answered to understand how organic solar cells operate and should be improved is how the orientation of the donor and acceptor molecules at the interface influences exciton diffusion, exciton dissociation by electron transfer, and recombination. It is exceedingly difficult to probe the orientation in bulk heterojunctions because there are many interfaces and they are arranged with varying angles with respect to the substrate. One of the best ways to study the interface is to make bilayer solar cells with just one donor–acceptor interface. Zinc phthalocyanine is particularly interesting to study because its orientation can be adjusted by using a 2 nm-thick copper iodide seed layer before it is deposited. Previous studies have claimed that solar cells in which fullerene acceptor molecules touch the face of zinc phthalocyanine have more current than ones in which the fullerenes touch the edge of zinc phthalocyanine because of suppressed recombination. We have more...

Isoindigo (iI) has proven successful as an electron-accepting building block for the preparation of electroactive materials for organic electronics. Its high yielding and scalable synthesis has enabled the rapid development of a large number of molecular and polymeric iI-based materials with remarkable physical properties. This perspective provides an overview of the fundamental properties of isoindigo and summarizes the progress in the development of new materials for varied electronic applications during the last 3 years, focusing in particular on organic photovoltaics (OPVs) and organic field effect transistors (OFETs). The fundamental electronic properties of isoindigo are discussed in the context of the substitution pattern effect (5,5′ vs 6,6′) on the frontier orbitals energies and optical properties. The development of molecular systems in the 6,6′-iI configuration for OPVs is examined with an emphasis on molecular design for improved electronic properties thanks to fine-tuning of the active layer ...

A family of π-extended platinum(II) porphyrins has been synthesized and incorporated into solution processed polymer light emitting diodes (PLEDs) and vapor deposited multilayer organic light emitting diodes (OLEDs), giving rise to devices with peak emission ranging from 771 to 1005 nm. The longest wavelength emitter, platinum(II)-5,10,15,20-(3,5-di-tert-butylphenyl)tetraanthroporphyrin (Pt-Ar4TAP), shows an emission maximum at 1005 nm, an external quantum efficiency (EQE) of 0.12%, and a maximum radiant emittance (Rmax) of 0.23 mW/cm2 in single layer PLED architectures, which is enhanced to an EQE of 0.20% with an Rmax of 0.57 mW/cm2 upon vapor deposition of an electron transport layer. In an effort to understand substituent effects and enhance the performance of π-extended Pt-porphyrins in PLEDs and OLEDs, a family of Pt-tetrabenzoporphyrins (Pt-TBPs) with varying functionality was investigated. The luminescent lifetimes of the Pt-TBPs in solution and in films were measured, and a strong correlation was...

A family of multi-heterocycle donor–acceptor–donor (DAD) telechelic conjugated oligomers designed for two-photon absorption (2PA) and emission in the near-infrared (near-IR) were prepared, and the relationship between their spectral, structural, and electrochemical properties were investigated. These oligomers, based on electron-rich thiophene, phenylene, and 3,4-ethylenedioxythiophene (EDOT) units as donors along with electron-deficient benzothiadiazole or its derivative units as acceptors, have been characterized through linear absorbance and fluorescence measurements, nonlinear absorbance, cyclic voltammetry, and differential pulse voltammetry to demonstrate the evolution of narrow HOMO–LUMO gaps ranging from 1.05 to 1.95 eV, with the oligomers composed of EDOT and benzo[1,2-c,3,4-c′]bis[1,2,5]thiadiazole (BBT) exhibiting the narrowest gap. The absorption maxima ranges from 517 to 846 nm and the fluorescence maxima ranges from 651 to 1088 nm for the different oligomers. Z-scan and two-photon fluorescen...

An amphiphilic diketopyrrolopyrrole-based oligothiophene (DPPamphi) has been prepared that displays robust self-assembly behavior in the bulk, in solution, and on surfaces. The material has been used as the active component in organic field-effect transistors and molecular bulk-heterojunction solar cells.