Enhancing the Performance of Polymer Solar Cells by Using Donor Polymers Carrying Discretely Distributed Side Chains

Xue Gong; Guangwu Li; Yang Wu; Jicheng Zhang; Shiyu Feng; Yahui Liu; Cuihong Li; Wei Ma; Zhishan Bo

doi:10.1021/acsami.7b04369

Enhancing the Performance of Polymer Solar Cells by Using Donor Polymers Carrying Discretely Distributed Side Chains

ACS Appl Mater Interfaces. 2017 Jul 19;9(28):24020-24026. doi: 10.1021/acsami.7b04369. Epub 2017 Jul 3.

Authors

Xue Gong¹, Guangwu Li¹, Yang Wu², Jicheng Zhang¹, Shiyu Feng¹, Yahui Liu¹, Cuihong Li¹, Wei Ma², Zhishan Bo¹

Affiliations

¹ Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University , Beijing 100875, China.
² State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University , No. 28 Xianning West Road, Xi'an 710049, China.

PMID: 28631466
DOI: 10.1021/acsami.7b04369

Abstract

Conjugated polymers with three components, P1-1 and P1-2, were prepared by one-pot Stille polymerization. The two-component polymer P1-0 is only composed of a 5-fluoro-6-alkyloxybenzothiadiazole (AFBT) acceptor unit and a thiophene donor unit, while the three-component polymers P1-1 and P1-2 contain 10% and 20% 5,6-difluorobenzothiadiazole (DFBT), respectively, as the third component. The incorporation of the third component, 5,6-difluorobenzothiadiazole, makes the side chains discretely distributed in the polymer backbones, which can enhance the π-π stacking of polymers in film, markedly increase the hole mobility of active layers, and improve the power-conversion efficiency (PCE) of devices. Influence of the third component on the morphology of active layer was also studied by X-ray diffraction (XRD), resonant soft X-ray scattering (R-SoXS), and transmission electron microscopy (TEM) experiments. P1-1/PC₇₁BM-based PSCs gave a high PCE up to 7.25%, whereas similarly fabricated devices for P1-0/PC₇₁BM only showed a PCE of 3.46%. The PCE of P1-1/PC₇₁BM-based device was further enhanced to 8.79% after the use of 1,8-diiodooctane (DIO) as the solvent additive. Most importantly, after the incorporation of 10% 5,6-difluorobenzothiadiazole unit, P1-1 exhibited a marked tolerance to the blend film thickness. Devices with a thickness of 265 nm still showed a PCE above 8%, indicating that P1-1 is promising for future applications.

Keywords: film thickness; morphology; power-conversion efficiency; side chains; solar cells; three-component conjugated polymers.