標題: Competition between Fullerene Aggregation and Poly(3-hexylthiophene) Crystallization upon Annealing of Bulk Heterojunction Solar Cells
作者: Wu, Wei-Ru
Jeng, U-Ser
Su, Chun-Jen
Wei, Kung-Hwa
Su, Ming-Shin
Chiu, Mao-Yuan
Chen, Chun-Yu
Su, Wen-Bin
Su, Chiu-Hun
Su, An-Chung
材料科學與工程學系
Department of Materials Science and Engineering
關鍵字: GISAXS;GIWAXS;structural kinetics;bulk heterojunction solar cells;charge mobility
公開日期: 1-Aug-2011
摘要: Concomitant development of [6,6]-phen-C(61)-butyric acid methyl ester (PCBM) aggregation and poly(3-hexylthiophene) (P3HT) crystallization in bulk heterojunction (BHJ) thin-film (ca. 85 nm) solar cells has been revealed using simultaneous grazing incidence small-/wide-angle X-ray scattering (GISAXS/GIWAXS). With enhanced time and spatial resolutions (5 s/frame; minimum q approximate to 0.004 angstrom(-1)), synchrotron GISAXS has captured In detail the fast growth in size of PCBM aggregates from 7 to 18 nm within 100 s of annealing at 150 degrees C. Simultaneously observed is the enhanced crystallization of P3HT Into lamellae oriented mainly perpendicular but also parallel to the substrate. An Avrami analysis of the observed structural evolution indicates that the faster PCBM aggregation follows a diffusion-controlled growth process (confined by P3HT segmental motion), whereas-the slower development of crystalline P3HT nanograins is characterized by constant nucleation rate (determined by the degree. of supercooling and POW demixing). These two competing kinetics result in local phase separation with space filling PCBM and P3HT nanodomains less than 20 nm in size when annealing temperature is kept below 180 degrees C. Accompanying the morphological development is the synchronized Increase In electron and hole mobilities of the BHJ thin-film solar cells, revealing the sensitivity of the carrier transport of the device on the structural features of PCBM and P3HT nanodomains. Optimized structural parameters, including the aggregate size and mean spacing of the PCBM aggregates, are quantitatively correlated to the device performance; a comprehensive network structure of the optimized BHJ thin film is presented.
URI: http://dx.doi.org/10.1021/nn2010816
http://hdl.handle.net/11536/20704
ISSN: 1936-0851
DOI: 10.1021/nn2010816
期刊: ACS NANO
Volume: 5
Issue: 8
起始頁: 6233
結束頁: 6243
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