Effect of asymmetric solubility of diketopyrrolopyrrole-based polymers and PC71BMs in a binary solvent system on the performance of bulk heterojunction solar cells

Seon Kyoung Son, Hyo Sang Lee, Jae Seung Ha, Kyung Hwan Kim, Hae Jung Son, Min Jae Ko, Honggon Kim, Doh Kwon Lee, Jin Young Kim, Wonmok Lee, Sungnam Park, Dong Hoon Choi, Bongsoo Kim

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


In this study, we demonstrated the effective morphological control of polymer:fullerene blends using three separate solvent systems: chloroform (CF), CF:1,8-diiodooctane (DIO), and CF:o-dichlorobenzene (ODCB). The polymer:fullerene blends are composed of two diketopyrrolopyrrole (DPP)-based polymers of P(DPP-alt-QT) and P(DPP-alt-DTBSe) and a fullerene derivative of [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), i.e., P(DPP-alt-QT):PC71BM or P(DPP-alt-DTBSe):PC71BM. The CF:ODCB binary solvent exhibited the best photovoltaic performance among the three solvent systems for both polymer-based devices, although the CF:DIO also exhibited an improved performance compared to the CF system. By examining film morphology of the blend films, we found that the CF:ODCB enabled the most optimal nanoscale phase separation and the morphological features were strongly affected by the solubility of each material in the high boiling-point (BP) solvent. Specifically, the polymers have limited but slightly higher solubility in ODCB than in DIO, while the PC71BM molecules have a high solubility in both DIO and ODCB. Therefore, this work highlights that the optimally asymmetric solubility of each photoactive component in the high BP solvent is a critical factor to form the nanoscale, bicontinuous domains in the blend films and thereby to determine the performance of photovoltaic devices.

Original languageEnglish
Pages (from-to)232-240
Number of pages9
JournalSolar Energy Materials and Solar Cells
Publication statusPublished - 2014 May


  • Binary solvent system
  • Hole mobility
  • Morphology
  • Organic photovoltaics
  • Polymer solar cell
  • Power conversion efficiency

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films


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