Radiofrequency Schottky Diodes Based on p-Doped Copper(I) Thiocyanate (CuSCN).

Schottky diodes based on inexpensive materials that can be processed using simple manufacturing methods are of particular importance for the next generation of flexible electronics. Although a number of high-frequency n-type diodes and rectifiers have been demonstrated, the progress with p-type diodes is lagging behind, mainly due to the intrinsically low conductivities of existing p-type semiconducting materials that are compatible with low-temperature, flexible, substrate-friendly processes. Herein, we report on CuSCN Schottky diodes, where the semiconductor is processed from solution, featuring coplanar Al-Au nanogap electrodes (<15 nm), patterned via adhesion lithography.

14 GHz Schottky Diodes Using a p-Doped Organic Polymer.

The low carrier mobility of organic semiconductors and the high parasitic resistance and capacitance often encountered in conventional organic Schottky diodes hinder their deployment in emerging radio frequency (RF) electronics. Here, these limitations are overcome by combining self-aligned asymmetric nanogap electrodes (≈25 nm) produced by adhesion lithography, with a high mobility organic semiconductor, and RF Schottky diodes able to operate in the 5G frequency spectrum are demonstrated. C IDT-BT is used, as the high hole mobility polymer, and the impact of p-doping on the diode performance is studied.

Doped Organic Hole Extraction Layers in Efficient PbS and AgBiS Quantum Dot Solar Cells.

The efficiency of PbS quantum dot (QD) solar cells has significantly increased in recent years, strengthening their potential for industrial applications. The vast majority of state-of-the-art devices utilize 1,2-ethanedithiol (EDT)-coated PbS QD hole extraction layers, which lead to high initial performance, but result in poor device stability. While excellent performance has also been demonstrated with organic extraction layers, these devices include a molybdenum trioxide (MoO) layer, which is also known to decrease device stability.

Effect of the Organic Semiconductor Side Groups on the Structural and Electronic Properties of Their Interface with Dopants.

Two derivatives of [1]benzothieno[3,2-b][1]benzothiophene (BTBT), namely, 2,7-dioctyl-BTBT (C8-BTBT) and 2,7-diphenyl-BTBT (DPh-BTBT), belonging to one of the best performing organic semiconductor (OSC) families, have been employed to investigate the influence of the substitutional side groups on the properties of the interface created when they are in contact with dopant molecules. As a molecular p-dopant, the fluorinated fullerene CF is used because of its adequate electronic levels and its bulky molecular structure. Despite the dissimilarity introduced by the OSC film termination, dopant thin films grown on top adopt the same (111)-oriented FCC crystalline structure in the two cases.

Surface specificity and mechanistic pathway of de-fluorination of CF on coinage metals.

We provide experimental and theoretical understanding on fundamental processes taking place at room temperature when a fluorinated fullerene dopant gets close to a metal surface. By employing scanning tunneling microscopy and photoelectron spectroscopies, we demonstrate that the on-surface integrity of CF depends on the interaction with the particular metal it approaches. Whereas on Au(111) the molecule preserves its chemical structure, on more reactive surfaces such as Cu(111) and Ni(111), molecules interacting with the bare metal surface lose the halogen atoms and transform to C.

Double Beneficial Role of Fluorinated Fullerene Dopants on Organic Thin-Film Transistors: Structural Stability and Improved Performance.

The present work assesses improved carrier injection in organic field-effect transistors by contact doping and provides fundamental insight into the multiple impacts that the dopant/semiconductor interface details have on the long-term and thermal stability of devices. We investigate donor [1]benzothieno[3,2-]-[1]benzothiophene (BTBT) derivatives with one and two octyl side chains attached to the core, therefore constituting asymmetric (BTBT-C8) and symmetric (C8-BTBT-C8) molecules, respectively. Our results reveal that films formed out of the asymmetric BTBT-C8 expose the same alkyl-terminated surface as the C8-BTBT-C8 films do.

Impact of Nanomorphology on Surface Doping of Organic Semiconductors: The Pentacene-CF Interface.

Establishing the rather complex correlation between the structure and the charge transfer in organic-organic heterostructures is of utmost importance for organic electronics and requires spatially resolved structural, chemical, and electronic details. Insight into this issue is provided here by combining atomic force microscopy, Kelvin probe force microscopy, photoemission electron microscopy, and low-energy electron microscopy for investigating a case study. We select the interface formed by pentacene (PEN), benchmark among the donor organic semiconductors, and a p-type dopant from the family of fluorinated fullerenes.

Small Molecule/Polymer Blend Organic Transistors with Hole Mobility Exceeding 13 cm(2) V(-1) s(-1).

A ternary organic semiconducting blend composed of a small-molecule, a conjugated polymer, and a molecular p-dopant is developed and used in solution-processed organic transistors with hole mobility exceeding 13 cm(2) V(-1) s(-1) (see the Figure). It is shown that key to this development is the incorporation of the p-dopant and the formation of a vertically phase-separated film microstructure.

Combining ligand-induced quantum-confined stark effect with type II heterojunction bilayer structure in CdTe and CdSe nanocrystal-based solar cells.

We show that it is possible to combine several charge generation strategies in a single device structure, the performance of which benefits from all methods used. Exploiting the inherent type II heterojunction between layered structures of CdSe and CdTe colloidal quantum dots, we systematically study different ways of combining such nanocrystals of different size and surface chemistry and with different linking agents in a bilayer solar cell configuration. We demonstrate the beneficial use of two distinctly different sizes of NCs not only to improve the solar spectrum matching but also to reduce exciton binding energy, allowing their efficient dissociation at the interface.