title: Impact of the Crystalline Packing Structures on Charge Transport and Recombination via Alkyl Chain Tunability of DPP-Based Small Molecules in Bulk Heterojunction Solar Cells.
abstract: A series of small compound materials based on benzodithiophene (BDT) and diketopyrrolopyrrole (DPP) with three different alkyl side chains were synthesized and used for organic photovoltaics. These small compounds had different alkyl branches (i.e., 2-ethylhexyl (EH), 2-butyloctyl (BO), and 2-hexyldecyl (HD)) attached to DPP units. Thin films made of these compounds were characterized and their solar cell parameters were measured in order to systematically analyze influences of the different side chains of compounds on the film microstructure, molecular packing, and hence, charge-transport and recombination properties. The relatively shorter side chains in the small molecules enabled more ordered packing structures with higher crystallinities, which resulted in higher carrier mobilities and less recombination factors; the small molecule with the EH branches exhibited the best semiconducting properties with a power conversion efficiency of up to 5.54% in solar cell devices. Our study suggested that tuning the alkyl chain length of semiconducting molecules is a powerful strategy for achieving high performance of organic photovoltaics.
authors.affiliation: Advanced Materials Division, Korea Research Institute of Chemical Technology (KRICT) , Daejeon 305-600, Republic of Korea.|Chemical Convergence Materials Major, University of Science and Technology (UST) , Daejeon 305-350, Republic of Korea.
authors.forename: Chang Eun
authors.initials: CE
authors.lastname: Song
authors.affiliation: POSTECH Organic Electronics Laboratory, Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH) , Pohang 790-784, Republic of Korea.
authors.forename: Yu Jin
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: Advanced Materials Division, Korea Research Institute of Chemical Technology (KRICT) , Daejeon 305-600, Republic of Korea.|Chemical Convergence Materials Major, University of Science and Technology (UST) , Daejeon 305-350, Republic of Korea.
authors.forename: Sanjaykumar R
authors.initials: SR
authors.lastname: Suranagi
authors.affiliation: Advanced Materials Division, Korea Research Institute of Chemical Technology (KRICT) , Daejeon 305-600, Republic of Korea.|Chemical Convergence Materials Major, University of Science and Technology (UST) , Daejeon 305-350, Republic of Korea.
authors.forename: Gururaj P
authors.initials: GP
authors.lastname: Kini
authors.affiliation: Advanced Materials Division, Korea Research Institute of Chemical Technology (KRICT) , Daejeon 305-600, Republic of Korea.|Department of Physics, Sungkyunkwan University , 2066 Seobu-ro, Jangan-gu, Suwon-si, Gyeong Gi-do, Republic of Korea.
authors.forename: Sangheon
authors.initials: S
authors.lastname: Park
authors.affiliation: Advanced Materials Division, Korea Research Institute of Chemical Technology (KRICT) , Daejeon 305-600, Republic of Korea.|Chemical Convergence Materials Major, University of Science and Technology (UST) , Daejeon 305-350, Republic of Korea.
authors.forename: Sang Kyu
authors.initials: SK
authors.lastname: Lee
authors.affiliation: Advanced Materials Division, Korea Research Institute of Chemical Technology (KRICT) , Daejeon 305-600, Republic of Korea.|Chemical Convergence Materials Major, University of Science and Technology (UST) , Daejeon 305-350, Republic of Korea.
authors.forename: Won Suk
authors.initials: WS
authors.lastname: Shin
authors.affiliation: Advanced Materials Division, Korea Research Institute of Chemical Technology (KRICT) , Daejeon 305-600, Republic of Korea.|Chemical Convergence Materials Major, University of Science and Technology (UST) , Daejeon 305-350, Republic of Korea.
authors.forename: Sang-Jin
authors.initials: SJ
authors.lastname: Moon
authors.affiliation: Department of Chemistry, The Catholic University of Korea , Bucheon, Gyeong Gi-do 420-743, Republic of Korea.
authors.forename: In-Nam
authors.initials: IN
authors.lastname: Kang
authors.affiliation: POSTECH Organic Electronics Laboratory, Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH) , Pohang 790-784, Republic of Korea.
authors.forename: Chan Eon
authors.initials: CE
authors.lastname: Park
authors.affiliation: Advanced Materials Division, Korea Research Institute of Chemical Technology (KRICT) , Daejeon 305-600, Republic of Korea.|Chemical Convergence Materials Major, University of Science and Technology (UST) , Daejeon 305-350, Republic of Korea.
authors.forename: Jong-Cheol
authors.initials: JC
authors.lastname: Lee
keywords: alkyl chain length; benzodithiophene; bulk heterojunction solar cell; diketopyrrolopyrrole; small molecule solar cell