Synthesis of phenanthro[1,10,9,8-cdefg]carbazole-based conjugated polymers for organic solar cell applications

Preparation and Characterization of Quinoxaline-Pyrene-Based Conjugated Copolymers for Organic Photovoltaic Devices

In this study, two novel conjugated polymers, poly(4,5,9,10-tetrakis((2-ethylhexyl)oxy]pyrene-alt-2,3-bis(3-(octyloxy)phenyl)-5,8-di(2-thienyl)-6,7-difluoroquinoxaline) (PPyQxff) and poly(4,5,9,10-tetrakis((2-ethylhexyl)oxy)pyren-alt-2,3-bis(3-(octyloxy)phenyl)-5,8-di(2-thienyl)quinoxaline) (PPyQx), consisting of quinoxaline units with and without fluorine substituents, as electron-accepting moieties and pyrene flanked with dithienyl units as electron-donating moieties were prepared via Stille polymerization reactions for use as electron donor materials in bulk heterojunction (BHJ) solar cells. PPyQxff and PPyQx were characterized by X-ray powder diffraction (XRD), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), cyclic voltammetry (CV), UV−VIS absorption, and nuclear magnetic resonance (NMR) spectroscopy. PPyQxff and PPyQx revealed excellent solution processability in common organic solvents. PPyQxff and PPyQx presented decomposition temperatures above 300 °C. The inclusion of F atoms to the quinoxaline moiety made a slight reduction in the highest occupied molecular orbital (HOMO) level, relative to the unfluorinated polymer, but had no impact on the lowest unoccupied molecular orbital (LUMO) level. PPyQxff and PPyQx exhibited similar physical properties with strong and broad absorbance from 400 to 700 nm and an optical band-gap energy of 1.77 eV. The X-ray powder diffraction study indicated that PPyQxff possessed a reduced π–π stacking distance relative to PPyQx.

Synthesis of Phenanthro[1,10,9,8-cdefg]carbazole-Based Conjugated Polymers for Green-Selective Organic Photodiodes

A push-pull-type donor copolymer, named PP-TPD, was synthesized with the Suzuki coupling reaction using 6H-phenanthro[1,10,9,8-cdefg]carbazole (PCZ) as the donor unit and 1,3-bis(5-bromothiophen-2-yl)-5-octyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (TPD) as the acceptor unit. The synthesized PP-TPD was systematically investigated in terms of crystallinity and thermal, electrical, electrochemical, and optical properties. PP-TPD revealed green-selective absorption with a narrow full width at half-maximum of 138 nm. Green-selective organic photodiodes (OPDs) were constructed using PP-TPD as the green-absorbing donor and ZnO as the nonabsorbing acceptor material. The fabricated OPDs exhibited an extremely low dark current of 0.68 nA/cm² at -5 V and a high detectivity above 10¹² Jones at 550 nm. Moreover, they showed a sufficiently high 3-dB frequency and a linear dynamic range, similar to those of ideal-operating OPDs. The origin and physics background of the observed low dark current and high detectivity are discussed in detail.

Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds: Synthetic Routes, Properties, and Applications

Two-dimensionally extended, polycyclic heteroaromatic molecules (heterocyclic nanographenes) are a highly versatile class of organic materials, applicable as functional chromophores and organic semiconductors. In this Review, we discuss the rich chemistry of large heteroaromatics, focusing on their synthesis, electronic properties, and applications in materials science. This Review summarizes the historical development and current state of the art in this rapidly expanding field of research, which has become one of the key exploration areas of modern heterocyclic chemistry.

Perylene, Oligorylenes, and Aza-Analogs

An in-depth discussion of the properties of perylene is presented. Tuning the properties of perylene by introducing nitrogens is also explored. Finally, we do not discuss the synthesis and properties of oligorylenes functionalized with dicarboxyimide bonds.

Effects of alkyl chain length on the optoelectronic properties and performance of pyrrolo-perylene solar cells

While the impact of alkyl side-chain length on the photovoltaic properties of conjugated polymers and their performance in bulk heterojunction (BHJ) solar cells has been studied extensively, analogous studies on pyrrolo-perylene-based polymers have not received adequate attention. To explore these effects, we synthesized two copolymers based on N-annulated pyrrolo-perylene and consisting of cyano group substituents on thiophene vinylene thiophene units with two different alkyl groups of 2-decyltetradecyl and 7-decylnonadecyl, and we studied them with regard to chemical structure and photovoltaic performance. UV-vis spectroscopy and cyclic voltammetry studies showed that variations in alkyl chain length affect crystallization, light absorption, and the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels. These factors have a pronounced impact on the morphology of BHJ thin films and their charge carrier separation and transportation characteristics, which, in turn, influences photovoltaic properties.