The Novel Additive 1-Naphthalenethiol Opens a New Processing Route to Efficiency-Enhanced Polymer Solar Cells

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• 作者：Hong-Jyun Jhuo ; Sih-Hao Liao ; Yi-Lun Li ; Po-Nan Yeh ; Show-An Chen ; Wei-Ru Wu ; Chun-Jen Su ; Jey-Jau Lee ; Norifumi L. Yamada and U-Ser Jeng
• 刊名：Advanced Functional Materials
• 出版年：2016
• 出版时间：May 10, 2016
• 年：2016
• 卷：26
• 期：18
• 页码：3094-3104
• 全文大小：7654K
• ISSN：1616-3028

文摘

Polymer solar cells (PSCs) based on fullerene derivatives often require additives to optimize active layer morphology. Here, the novel additive 1-naphthalenethiol (SH-na) is proposed for processing the PSC active layer of PTB7:PC₇₁BM. Spin-casting with SH-na as additive achieves a power conversion efficiency (PCE) of 7.3%, compared to 6.7% for preparations containing the conventional 1,8-diiodooctane additive. Dipping of the active layer into a methanol solution of critical SH-na concentration increases the PCE further to 8.75%. This is mainly due to an improved open-circuit voltage (from 0.72 to 0.79 V) together with a high achieved fill factor of 0.70. The improved PCE is correlated to the morphology optimization according to measurements of grazing incidence small/wide-angle X-ray scattering, neutron reflectivity, atomic force microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The integrated results suggest that the halogen-free additive SH-na can form hydrogen bonds with both PTB7 and PC₇₁BM, resulting in substantially improved PTB7 crystallization and multi-length-scale PC₇₁BM dispersion for appropriate aggregation and networks. The subsequent dipping treatment with SH-na further modifies the active layer morphology for a more PC₇₁BM-enriched surface and better PC₇₁BM networks in the bulk film for an optimized electron-to-hole mobility ratio of 2.04, hence resulting in improved device performance.