title: Effect of fabrication parameters on three-dimensional nanostructures of bulk heterojunctions imaged by high-resolution scanning ToF-SIMS.
abstract: Solution processable fullerene and copolymer bulk heterojunctions are widely used as the active layers of solar cells. In this work, scanning time-of-flight secondary ion mass spectrometry (ToF-SIMS) is used to examine the distribution of [6,6]phenyl-C61-butyric acid methyl ester (PCBM) and regio-regular poly(3-hexylthiophene) (rrP3HT) that forms the bulk heterojunction. The planar phase separation of P3HT:PCBM is observed by ToF-SIMS imaging. The depth profile of the fragment distribution that reflects the molecular distribution is achieved by low energy Cs(+) ion sputtering. The depth profile clearly shows a vertical phase separation of P3HT:PCBM before annealing, and hence, the inverted device architecture is beneficial. After annealing, the phase segregation is suppressed, and the device efficiency is dramatically enhanced with a normal device structure. The 3D image is obtained by stacking the 2D ToF-SIMS images acquired at different sputtering times, and 50 nm features are clearly differentiated. The whole imaging process requires less than 2 h, making it both rapid and versatile.
authors.affiliation: Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Bang-Ying
authors.initials: BY
authors.lastname: Yu
authors.forename: Wei-Chun
authors.initials: WC
authors.lastname: Lin
authors.forename: Wei-Ben
authors.initials: WB
authors.lastname: Wang
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Iida
authors.forename: Sun-Zen
authors.initials: SZ
authors.lastname: Chen
authors.forename: Chia-Yi
authors.initials: CY
authors.lastname: Liu
authors.forename: Che-Hung
authors.initials: CH
authors.lastname: Kuo
authors.forename: Szu-Hsian
authors.initials: SH
authors.lastname: Lee
authors.forename: Wei-Lun
authors.initials: WL
authors.lastname: Kao
authors.forename: Guo-Ji
authors.initials: GJ
authors.lastname: Yen
authors.forename: Yun-Wen
authors.initials: YW
authors.lastname: You
authors.forename: Chi-Ping
authors.initials: CP
authors.lastname: Liu
authors.forename: Jwo-Huei
authors.initials: JH
authors.lastname: Jou
authors.forename: Jing-Jong
authors.initials: JJ
authors.lastname: Shyue