Achieving an Efficiency Exceeding 10% for Fullerene‐based Polymer Solar Cells Employing a Thick Active Layer via Tuning Molecular Weight. (11th December 2017)

• Record Type: Journal Article
• Authors: Li, Zelin; Yang, Dalei; Zhao, Xiaoli; Zhang, Tong; Zhang, Jidong; Yang, Xiaoniu
• Is Part Of: Advanced functional materials. Volume 28:Number 6(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-12-11
• Subjects: crystallinity -- mobility -- molecular weight -- polymer solar cells -- thick films; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201705257
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: Recently, the influence of molecular weight ( M n ) on the performance of polymer solar cells (PSCs) is widely investigated. However, the dependence of optimal thickness of active layer for PSCs on M n is not reported yet, which is vital to the solution printing technology. In this work, the effect of M n on the efficiency and especially optimal thickness of the active layer for PBTIBDTT‐S‐based PSCs is systematically studied. The device efficiency improves significantly as the M n increases from 12 to 38 kDa, and a remarkable efficiency of 10.1% is achieved, which is among the top efficiencies of wide‐bandgap polymer:fullerene PSCs. Furthermore, the optimal thickness of the active layer is also greatly increased from 62 to 210 nm with increased M n . Therefore, a device employing a thick (>200 nm) active layer with power conversion efficiency exceeding 10% is achieved by manipulating M n . This exciting result is attributed to both the improved crystallinity, thus hole mobility, and preferable polymer orientation, thus morphology of active layer. These findings, for the first time, highlight the significant impact of M n on the optimal thickness of active layer for PSCs and provide a facile way to further improve the performance of PSCs employing a thick active layer. Abstract : As the molecular weight ( M n ) of PBTIBDTT‐S increases from 12 to 38 kDa, the efficiency and optimal thickness of the active layer are simultaneously improved from 6.99% to 10.11% and from 62 to 210 nm, respectively. This result demonstrates the importance of M n in achieving highly efficient devices under a thick active layer.