Effect of fabrication parameters on three-dimensional nanostructures of bulk heterojunctions imaged by high-resolution scanning ToF-SIMS.
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.
Yu
Bang-Ying
BY
Research Center for Applied Sciences, Academia Sinica, Taipei 115, Taiwan.
Lin
Wei-Chun
WC
Wang
Wei-Ben
WB
Iida
Shin-Ichi
S
Chen
Sun-Zen
SZ
Liu
Chia-Yi
CY
Kuo
Che-Hung
CH
Lee
Szu-Hsian
SH
Kao
Wei-Lun
WL
Yen
Guo-Ji
GJ
You
Yun-Wen
YW
Liu
Chi-Ping
CP
Jou
Jwo-Huei
JH
Shyue
Jing-Jong
JJ