title: Efficient organic photovoltaics utilizing nanoscale heterojunctions in sequentially deposited polymer/fullerene bilayer.
abstract: A highly efficient sequentially deposited bilayer (SD-bilayer) of polymer/fullerene organic photovoltaic (OPV) device is developed via the solution process. Herein, we resolve two essential problems regarding the construction of an efficient SD-bilayer OPV. First, the solution process fabrication of the SD-bilayer is resolved by incorporating an ordering agent (OA) to the polymer solution, which improves the ordering of the polymer chain and prevents the bottom-layer from dissolving into the top-layer solution. Second, a non-planar heterojunction with a large surface area is formed by the incorporation of a heterojunction agent (HA) to the top-layer solution. Poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT) is used for the bottom-layer and phenyl-C71-butyric-acid-methyl ester (PC70BM) is used for the top-layer. The SD-bilayer OPV produced utilizing both an OA and HA exhibits a power conversion efficiency (PCE) of 7.12% with a high internal quantum efficiency (IQE). We believe our bilayer system affords a new way of forming OPVs distinct from bulk heterojunction (BHJ) systems and offers a chance to reconsider the polymers that have thus far shown unsatisfactory performance in BHJ systems.
authors: Department of Chemistry and Nano Science, Global Top 5 Research Program, Ewha Womans University, Seoul 120-750, Republic of Korea.
authors: Jeesoo
authors: J
authors: Seok
authors: Pohang Accelerator Laboratory, Pohang, Kyungbuk 790-784, Republic of Korea.
authors: Tae Joo
authors: TJ
authors: Shin
authors: Department of Chemical and Biomolecular Engineering, Yonsei University, Seoul 120-749, Republic of Korea.
authors: Sungmin
authors: S
authors: Park
authors: Graduate School of Energy, Environment, Water, and Sustainability (EEWS), Graphene Research Center, KAIST, Daejeon 305-701, Republic of Korea.
authors: Changsoon
authors: C
authors: Cho
authors: Graduate School of Energy, Environment, Water, and Sustainability (EEWS), Graphene Research Center, KAIST, Daejeon 305-701, Republic of Korea.
authors: Jung-Yong
authors: JY
authors: Lee
authors: Department of Chemical and Biomolecular Engineering, Yonsei University, Seoul 120-749, Republic of Korea.
authors: Du
authors: D
authors: Yeol Ryu
authors: Department of Chemistry and Nano Science, Global Top 5 Research Program, Ewha Womans University, Seoul 120-750, Republic of Korea.
authors: Myung Hwa
authors: MH
authors: Kim
authors: Department of Chemistry and Nano Science, Global Top 5 Research Program, Ewha Womans University, Seoul 120-750, Republic of Korea.
authors: Kyungkon
authors: K
authors: Kim