Donor polymer based on alkylthiophene side chains for efficient non-fullerene organic solar cells: insights into fluorination and side chain effects on polymer aggregation and blend morphology. Issue 46 (14th November 2018)

• Record Type: Journal Article
• Authors: Liu, Jing; Ma, Lik-Kuen; Li, Zhengke; Hu, Huawei; Sheong, Fu Kit; Zhang, Guangye; Ade, Harald; Yan, He
• Is Part Of: Journal of materials chemistry. Volume 6:Issue 46(2018)
• Page Start: 23270
• Page End: 23277
• Publication Date: 2018-11-14
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c8ta08769e
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : The synergistic effects of overfluorination and alkylthiophene side chain strategies led to 10.60% efficiency for non-fullerene organic solar cells. Abstract : Reducing the voltage loss is considered a promising route to improve the performance of organic solar cells (OSCs). In this work, two donor polymers PT4FB and PTT4FB based on a tetra-fluorinated benzene building block are synthesized and applied to non-fullerene OSC devices, which achieve high open-circuit voltage ( V OC ). When PT4FB is combined with IDIC, the blend exhibits large fiber-like domains (size ∼39 nm) due to the excessive aggregation of PT4FB, which results in a relatively low short-circuit current ( J SC ) of 14.06 mA cm −2 and a moderate power conversion efficiency (PCE) of 9.81%. To weaken the aggregation of PT4FB, we replace the alkyl chains on the polymer backbone with alkylthiophene side chains to afford a novel donor polymer PTT4FB with reduced packing and crystallinity. As a result, the PTT4FB:IDIC-based blend shows significantly smaller domain sizes (24 nm) than the PT4FB-based device, contributing to a remarkably increased J SC and an overall higher PCE of 10.60%. The synergistic effects of abundant fluorination and alkylthiophene side chains can be utilized as a general method to tune the morphological and energetic properties when designing novel donor polymers to achieve both high V OC and favorable morphology for efficient non-fullerene OSCs.