Synthesis and characterization of p-type conductivity dopant 2-(3-(adamantan-1-yl)propyl)-3,5,6-trifluoro-7,7,8,8-tetracyanoquinodimethane

Abstract

We report the synthesis and characterization of 2-(3-(adamantan-1-yl)propyl)-3,5,6-trifluoro-7,7,8,8tetracyanoquinodimethane (F3TCNQ-Ad1), a substituted analog of 2, 3,5,7,8,8tetracyanoquinodimethane (F4TCNQ), designed for p-type conductivity doping. The dopant is designed as a model for substituted alternatives to F4TCNQ that maintain similar electronic properties with the goal of engineering dopants with superior fabrication characteristics over F4TCNQ. We describe the design strategy for F3TCNQ-Ad1 based on molecular modeling predictions that substitution of a single fluorine atom of F4TCNQ has little effect on the electronic properties of the molecule. Photophysical and electrochemical characterization reveal that the adamantyl substituent in F3TCNQ-Ad1 does not significantly alter the electronic properties of the substituted dopant relative to F4TCNQ. Unfortunately, F3TCNQ-Ad1 degrades under standard sublimation conditions, preventing sublimation deposition processing. Instead, hole-only devices were made via solution-processing of the p-doped films with the structure glass/ITO/2.3 Â 10 3 Å PVK:(MTDATA:dopant)/2.0 Â 10 2 Å Au/1.0 Â 10 3 Å Al, where dopant is either F4TCNQ or F3TCNQ-Ad1. We demonstrate that F3TCNQ-Ad1 increased the conductivity of the films by at least 1000 times compared to an undoped device.

Increasing Polymer Solar Cell Fill Factor by Trap‐Filling with F4‐TCNQ at Parts Per Thousand Concentration

“…Specifically, the high‐efficiency polymer, poly[4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b;4,5‐b′]dithiophene‐2,6‐diyl‐alt‐(4‐(2‐ethylhexyl)‐3‐fluorothieno[3,4‐b]thiophene‐)‐2‐carboxylate‐2‐6‐diyl)] (PBDTTT‐EFT) was treated with low concentrations of F4‐TCNQ. Ground state electron transfer is expected to occur from the polymer to F4‐TCNQ ( Figure a) . The ground state electron transfer is supported by the onset of absorption peak in infrared region and this peak is not observed with equal content of 7,7,8,8‐tetracyanoquinodimethane (TCNQ) having −4.5 eV lowest unoccupied molecular orbital (LUMO) level (Figure S1 in the Supporting Information) .…”

Controlling Molecular Doping in Organic Semiconductors

“…Finally, structural modifications of F4TCNQ have been made with the goal of reducing the unwanted diffusion of the dopant. One strategy is to replace a fluorine with a bulkier side group . A similar synthetic strategy is to replace a nitrile with a tailorable ester .…”

Substituted Molecular <i>p</i>-Dopants: A Theoretical Study

“…A molecule very similar to F3-TCNQ 1 was synthesized and studied. The predicted LUMO state of molecule F3-ad1 was destabilized by 0.3 eV compared to F4-TCNQ [14]. F3-adl was successfully used as a molecular pdopant for light emitting devices and thin film transistors [15].…”