A naphthodithiophene-based nonfullerene acceptor for high-performance polymer solar cells with a small energy loss

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2020-05, Vol.8 (19), p.6513-652
• Main Authors: Dong, Xingliang, Guo, Qing, Liu, Qi, Zhu, Lei, Guo, Xia, Liu, Feng, Zhang, Maojie
• Format: Article
• Language: English
• Subjects: Circuits; Energy conversion efficiency; Energy dissipation; Energy gap; Energy levels; Heat treatment; Molecular orbitals; Open circuit voltage; Photovoltaic cells; Polymers; Short circuit currents; Solar cells
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d0tc00270d

Introducing intramolecular noncovalent interactions is an effective method for enlarging the conjugated area of the donor core in nonfullerene acceptors (NFAs) to improve the photovoltaic performance. In this study, a novel NFA (NTO-4F) based on a para -substituted naphtho[1,2- b :5,6- b ′]dithiophene core with alkoxy side chains was designed and synthesized, which has a featured oxygen atom at the side chains to facilitate an intramolecular noncovalent S-O interaction with thiophene at the core. NTO-4F exhibits strong absorption in the 600 to 800 nm region with a narrow optical band gap of 1.55 eV, suitable energy levels with a high-lying lowest unoccupied molecular orbital (LUMO) of −3.88 eV, and appropriate crystallinity. As a result, when NTO-4F is blended with the wide bandgap polymer, PM6, as the active layer, the optimized polymer solar cells (PSCs) achieve a power conversion efficiency (PCE) of 11.5% with simultaneously high open-circuit voltage ( V oc ) of 0.99 V and short-circuit current density ( J sc ) of 19.1 mA cm −2 , attributing to the low energy loss of 0.56 eV. Furthermore, PM6:NTO-4F-based devices exhibit excellent tolerance to thermal annealing (TA) treatment with over 10% PCEs for all devices under TA treatment from 140 to 200 °C and over 80% of the initial PCE after thermal treatment at 180 °C for 45 min. A new non-fullerene acceptor named NTO-4F is developed. The optimal PSC based on PM6:NTO-4F achieves a PCE of 11.5% with simultaneously high open-circuit voltage of 0.99 V and short-circuit current density of 19.1 mA cm −2 .