title: Selective Morphology Control of Bulk Heterojunction in Polymer Solar Cells Using Binary Processing Additives.
abstract: We report the effect of binary additives on the fabrication of polymer solar cells (PSCs) based on a bulk heterojunction (BHJ) system. The combination of 1,8-diiodooctane (DIO), a high-boiling and selective solvent, for fullerene derivatives and poly(dimethylsiloxane) (PDMS) precursor, a nonvolatile insulating additive, affords complementary functions on the effective modulation of BHJ morphology. It was found that DIO and PDMS precursor each play different roles in the control of BHJ morphology, and thus, the power conversion efficiency (PCE) can be further enhanced to 7.6% by improving the fill factor (FF) from 6.8% compared to that achieved using a conventional device employing only a DIO additive. In the BHJ of the active layer, DIO suppressed the large phase separation of PBDTTT-CF and PC71BM while allowing the formation of continuous polymer networks in the donor polymer through phase separation of the PDMS precursor and BHJ components. The appropriate amount of PDMS precursor does not disturb charge transport in the BHJ despite having insulating properties. In addition, the dependence of photovoltaic parameters on different light intensities reveals that the charge recombination in the device with DIO and PDMS precursor decreases compared to that achieved using the device with only DIO.
authors.affiliation: School of Materials Science and Engineering, Research Institute for Solar and Sustainable Energies, Gwangju Institute of Science and Technology (GIST) , 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712, Republic of Korea.
authors.forename: Yen-Sook
authors.initials: YS
authors.lastname: Jung
authors.affiliation: Carbon Convergence Materials Research Center, Institute of Advanced Composite Materials, Korea Institute of Science and Technology (KIST) , Wanju-gun, Jeollabuk-do 55324, Korea.
authors.forename: Jun-Seok
authors.initials: JS
authors.lastname: Yeo
authors.affiliation: Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology (GIST) , 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712, Republic of Korea.
authors.forename: Nam-Koo
authors.initials: NK
authors.lastname: Kim
authors.affiliation: School of Materials Science and Engineering, Research Institute for Solar and Sustainable Energies, Gwangju Institute of Science and Technology (GIST) , 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712, Republic of Korea.
authors.forename: Sehyun
authors.initials: S
authors.lastname: Lee
authors.affiliation: School of Materials Science and Engineering, Research Institute for Solar and Sustainable Energies, Gwangju Institute of Science and Technology (GIST) , 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712, Republic of Korea.
authors.forename: Dong-Yu
authors.initials: DY
authors.lastname: Kim
keywords: DIO; PDMS resin; binary additives; bulk heterojunction; polymer solar cells