High‐Efficiency Organic Photovoltaics using Eutectic Acceptor Fibrils to Achieve Current Amplification

• Published in: Advanced materials (Weinheim) Vol. 33; no. 18; pp. e2007177 - n/a
• Main Authors: Zhang, Ming, Zhu, Lei, Hao, Tianyu, Zhou, Guanqing, Qiu, Chaoqun, Zhao, Zhe, Hartmann, Nicolai, Xiao, Biao, Zou, Yecheng, Feng, Wei, Zhu, Haiming, Zhang, Maojie, Zhang, Yongming, Li, Yongfang, Russell, Thomas P., Liu, Feng
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.05.2021
• Subjects: Amplification; Carrier transport; Charge transfer; Crystal defects; Crystal structure; Crystallinity; Energy conversion efficiency; Energy levels; eutectic mixtures; Eutectics; Heterojunctions; Materials science; Morphology; nonfullerene acceptors; organic photovoltaics; Photovoltaic cells; Physical properties; Solar cells; Thin films; nonfullerene acceptors; eutectic mixtures; organic photovoltaics
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202007177

The intrinsic electronic properties of donor (D) and acceptor (A) materials in coupling with morphological features dictate the output in organic solar cells (OSCs). New physical properties of intimate eutectic mixing are used in nonfullerene‐acceptor‐based D–A1–A2 ternary blends to fine‐tune the bulk heterojunction thin film morphology as well as their electronic properties. With enhanced thin film crystallinity and improved carrier transport, a significant JSC amplification is achieved due to the formation of eutectic fibrillar lamellae and reduced defects state density. Material wise, aligned cascading energy levels with much larger driving force, and suppressed recombination channels confirm efficient charge transfer and transport, enabling an improved power conversion efficiency (PCE) of 17.84%. These results reveal the importance of utilizing specific material interactions to control the crystalline habit in blended films to form a well‐suited morphology in guiding superior performances, which is of high demand in the next episode of OSC fabrication toward 20% PCE. Ternary organic solar cells are fabricated, achieving a significant JSC boost by virtue of an optimized crystalline feature with the formation of a eutectic mixture with better acceptor crystalline fibrils. The optimal morphology suppresses energetic disorder and recombination and increases charge transfer and transport, yielding a high efficiency of 17.84% with significant current boost.