Thermally stable bulk heterojunction prepared by sequential deposition of nanostructured polymer and fullerene

Heewon Hwang, Hoyeon Lee, Shafidah Shafian, Wooseop Lee, Jeesoo Seok, Ka Yeon Ryu, Du Yeol Ryu, Kyungkon Kim

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23 Scopus citations


A morphologically-stable polymer/fullerene heterojunction has been prepared by minimizing the intermixing between polymer and fullerene via sequential deposition (SqD) of a polymer and a fullerene solution. A low crystalline conjugated polymer of PCPDTBT (poly[2,6-(4,4- bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b0]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]) has been utilized for the polymer layer and PC71BM (phenyl-C71-butyric-acid-methyl ester) for the fullerene layer, respectively. Firstly, a nanostructured PCPDTBT bottom layer was developed by utilizing various additives to increase the surface area of the polymer film. The PC71BM solution was prepared by dissolving it in the 1,2-dichloroethane (DCE), exhibiting a lower vapor pressure and slower diffusion into the polymer layer. The deposition of the PC71BM solution on the nanostructured PCPDTBT layer forms an inter-digitated bulk heterojunction (ID-BHJ) with minimized intermixing. The organic photovoltaic (OPV) device utilizing the ID-BHJ photoactive layer exhibits a highly reproducible solar cell performance. In spite of restricted intermixing between the PC71BM and the PCPDTBT, the efficiency of ID-BHJ OPVs (3.36%) is comparable to that of OPVs (3.87%) prepared by the conventional method (deposition of a blended solution of polymer:fullerene). The thermal stability of the ID-BHJ is superior to the bulk heterojunction (BHJ) prepared by the conventional method. The ID-BHJ OPV maintains 70% of its initial efficiency after thermal stress application for twelve days at 80 °C, whereas the conventional BHJ OPV maintains only 40% of its initial efficiency.

Original languageEnglish
Article number456
Issue number9
StatePublished - 17 Sep 2017

Bibliographical note

Funding Information:
Acknowledgments: This research was supported by NRF under the program numbers NRF-2015M1A2A2057506 and NRF-2016M1A2A2940914 and by the New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), who granted financial resources from the Ministry of Trade, Industry & Energy, Republic of Korea. (No. 20123010010140 and 20163030013900). The authors thank Mr. Sungmin Park and Mr. Yeongsik Kim for assistance with the GIWAXS characterization. The X-ray experiments at PLS-II (Beamline 9A U-SAXS), Korea, were supported in part by MSIP and POSTECH.

Publisher Copyright:
© 2017 by the authors.


  • Bulk heterojunction
  • Organic solar cell
  • Sequential deposition
  • Stability


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