Performance Improvement of PTB7:PC71BM Bulk Heterojunction Solar Cells by Adding Multiple Surfactants

Masaya OHZEKI  Shunjiro FUJII  Hiromichi KATAURA  Yasushiro NISHIOKA  

IEICE TRANSACTIONS on Electronics   Vol.E99-C   No.5   pp.551-554
Publication Date: 2016/05/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E99.C.551
Type of Manuscript: BRIEF PAPER
BHJ solar cells,  PTB7,  PC71BM,  DMSO,  DIO,  

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We fabricated bulk heterojunction organic solar cells based on 1,2-dichlorobenzene solutions of poly[[4,8-bis[(2-ethylhexyl) oxy]benzo[1,2-b:4,5-b'] dithiophene-2,6-diyl] [3-fluoro-2-[(2-ethylhexyl) carbonyl]thieno [3,4-b]-thiophenediyl]] (PTB7): [6,6]-phenyl-C71-butyric-acid-methyl-ester (PTB7:PC71BM) with additional dimethyl sulfoxide (DMSO) and surfactants diiodooctane (DIO). The optimal weight ratios of DMSO and DIO relative to the total weight of PTB7:PC71BM were 13% and 3%, respectively, and the resulting solar cells exhibited an open circuit voltage of 0.72 V, short circuit current density of 15.63 mA/cm2, fill factor of 0.49, and power conversion efficiency of 5.47%. The surfaces of the active layers deposited with added DMSO and DIO were smoother than those of the layers without the added surfactants and consisted of smaller nanograins, which may have resulted in the improved solar cell performance.