D‐A Polymer with a Donor Backbone ‐ Acceptor‐side‐chain Structure for Organic Solar Cells

Wide Bandgap Polymer Donors Based on Succinimide-Substituted Thiophene for Nonfullerene Organic Solar Cells

The advent of nonfullerene acceptors (NFAs) has greatly improved the photovoltaic performance of organic solar cells (OSCs). However, to compete with other solar cell technologies, there is a pressing need for accelerated research and development of improved NFAs as well as their compatible wide bandgap polymer donors. In this study, a novel electron-withdrawing building block, succinimide-substituted thiophene (TS), is utilized for the first time to synthesize three wide bandgap polymer donors: PBDT-TS-C5, PBDT-TSBT-C12, and PBDTF-TSBT-C16. These polymers exhibit complementary bandgaps for efficient sunlight harvesting and suitable frontier energy levels for exciton dissociation when paired with the extensively studied NFA, Y6. Among these donors, PBDTF-TSBT-C16 demonstrates the highest hole mobility and a relatively low highest occupied molecular orbital (HOMO) energy level, attributed to the incorporation of thiophene spacers and electron-withdrawing fluorine substituents. OSC devices based on the blend of PBDTF-TSBT-C16:Y6 achieve the highest power conversion efficiency of 13.21%, with a short circuit current density (Jsc) of 26.83 mA cm-2, an open circuit voltage (Voc) of 0.80 V, and a fill factor of 0.62. Notably, the Voc × Jsc product reaches 21.46 mW cm-2, demonstrating the potential of TS as an electron acceptor building block for the development of high-performance wide bandgap polymer donors in OSCs.

Derivatives of diphenylamine and benzothiadiazole in optoelectronic applications: a review

Light-emitting conjugated organic compounds have found special interest among researchers. Because of their adjustable optoelectronic properties they can be applied in e.g. field-effect transistors, sensors, light-emitting diodes or photovoltaic cells. In order to develop high-performance systems, it is important to understand the relationship between the structure and the photophysical properties of the material used. One of the employed strategies is to decrease the band gap of conjugated compounds, often achieved through a “donor–acceptor” approach. One of the popular groups applied as an electron-accepting unit are benzothiadiazoles, while diphenylamine exhibits good electron-donating ability. The functional groups can affect the energy levels of materials, influencing the color of the light emitted. This work presents a review of research focused on the structure-properties relationship of diphenylamine and benzothiadiazole derivatives with optoelectronic applications.

Wide Bandgap Polymer Donor with Acrylate Side Chains for Non-Fullerene Acceptor-based Organic Solar Cells

Organic semiconductors inherently have a low dielectric constant and hence high exciton binding energy, which is largely responsible for the rather low power conversion efficiency of organic solar cells as well as the requirements to achieve delicate bulk-heterojunction nanophase separation in the active layer. In this study, we use methyl acrylate as a weakly electron-withdrawing side chain for the electron rich thiophene to prepare a new building block, methyl thiophene-3-acrylate (TA), with increased polarity. A wide bandgap polymer PBDT-TA synthesized using TA and a benzodithiophene (BDT) monomer shows increased dielectric constant and reduced exciton binding energy compared to the analogous polymer PBDT-TC, which is made of BDT and methyl thiophene-3-carboxylate (TC). An organic solar cell device based on PBDT-TA:ITIC also achieves a higher power conversion efficiency of 10.47% than that of the PBDT-TC:ITIC based solar cell (9.68%). This work demonstrates the effectiveness of using acrylate side chains to increase the dielectric constant, reduce the exciton binding energy, and enhance the solar cell efficiency of polymer semiconductors. This article is protected by copyright. All rights reserved.

Synthesis of a Low-Cost Thiophene-Indoloquinoxaline Polymer Donor and Its Application to Polymer Solar Cells

A simple wide-bandgap conjugated polymer based on indoloquinoxaline unit (PIQ) has been newly designed and synthesized via cheap and commercially available starting materials. The basic physicochemical properties of the PIQ have been investigated. PIQ possesses a broad and strong absorption band in the wavelength range of 400~660 nm with a bandgap of 1.80 eV and lower-lying highest occupied molecular orbital energy level of −5.58 eV. Polymer solar cells based on PIQ and popular acceptor Y6 blend display a preliminarily optimized power conversion efficiency of 6.4%. The results demonstrate indoloquinoxaline is a promising building unit for designing polymer donor materials for polymer solar cells.