Phenothiazine‐Based Donor–Acceptor Polymers as Multifunctional Materials for Charge Storage and Solar Energy Conversion

• Published in: Macromolecular rapid communications. 2024-01, Vol.45 (1), p.e2200699-n/a
• Main Authors: Wessling, Robin, Delgado Andrés, Rodrigo, Morhenn, Isabel, Acker, Pascal, Maftuhin, Wafa, Walter, Michael, Würfel, Uli, Esser, Birgit
• Format: Article
• Language: English
• Subjects: Batteries; Block copolymers; Charge materials; Copolymers; Design; Donor materials; donor–acceptor polymers; Electrode materials; Energy charge; Energy conversion; Energy conversion efficiency; Energy demand; Energy storage; Heterojunctions; level alignment; Lithium; Multifunctional materials; organic batteries; organic solar cells; Phenothiazine; Photovoltaic cells; Photovoltaics; Polymers; redox polymers; rotation potentials; Solar cells; Solar energy; Solar energy conversion
• ISSN: 1022-1336; 1521-3927
• DOI: 10.1002/marc.202200699

The increasing energy demand for diverse applications requires new types of devices and materials. Multifunctional materials that can fulfill different roles are of high interest as they can allow fabricating devices that can both convert and store energy. Herein, organic donor–acceptor redox polymers that can function as charge storage materials in batteries and as donor materials in bulk heterojunction (BHJ) photovoltaic devices are investigated. Based on its reversible redox chemistry, phenothiazine is used as the main building block in the conjugated copolymer design and combined with diketopyrrolopyrrol and benzothiadiazole as electron‐poor comonomers to shift the optical absorption into the visible region. The resulting polymers show excellent cycling stability as positive electrode materials in lithium–organic batteries at discharge potentials of 3.6–3.7 V versus Li/Li+ as well as good performances in BHJ solar cells with up to 1.9% power conversion efficiency. This study shows that the design of such multifunctional materials is possible, however, that it also faces challenges, as essential properties for good device function can lead to diametrically opposite requirements in materials design. Phenothiazine‐based polymers are designed such that they can both reversibly store charge in batteries and harvest light for bulk heterojunction solar cells. This multifunctionality is enabled through the presence of phenothiazine units as excellent redox centers combined with a donor–acceptor conjugated copolymer design to shift the absorption into the visible range.