Morphology-performance relationships in polymer/fullerene blends probed by complementary characterisation techniques - effects of nanowire formation and subsequent thermal annealing
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SCOPUS
- Title
- Morphology-performance relationships in polymer/fullerene blends probed by complementary characterisation techniques - effects of nanowire formation and subsequent thermal annealing
- Authors
- Kim, JS; Wood, S; Shoaee, S; Spencer, SJ; Castro, FA; Tsoi, WC; Murphy, CE; Sim, M; Cho, K; Durrant, JR; Kim, JS
- Date Issued
- 2015-08
- Publisher
- ROYAL SOC CHEMISTRY
- Abstract
- We report detailed analysis of the thin film morphology (molecular packing, molecular conformational order, and vertical phase separation) - performance (charge transport, photocurrent generation, and photovoltaic performance) relationships under nanowire formation and subsequent thermal annealing in polymer: fullerene blends. Nanowires of poly(3-hexylthiophene) (P3HT) are formed by controlled precipitation from solution and blended with [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) to form bulk heterojunction thin films. The formation of nanowires and further thermal annealing result in increased molecular order of the P3HT, where the short-range conformational order is maximised by annealing at 100 degrees C and decreases when annealed at higher temperatures, but the quality of long-range molecular packing and lamellar packing distance increase with annealing temperature up to 150 degrees C. The long-range order correlates strongly with an increase in hole mobility, but the reduction in short-range conformational order indicates a slight reduction in planarity of the conjugated backbone in this aggregated polymer morphology. Photoconductive atomic force microscopy reveals enhanced connectivity of the hole transporting nanowire network as a result of thermal annealing. Additionally, we find that the nanowire morphology results in a favourable vertical phase separation, with PCBM enrichment at the electron-extracting surface in the conventional architecture, which is contrary to the non-nanowire case. This effect is further encouraged by thermal annealing, resulting in an enhancement of open-circuit voltage, and represents a morphological advantage over conventional P3HT: PCBM devices. Our study identifies an important interplay between long-range and short-range molecular order in charge generation, transport, extraction, and hence solar cell device performance.
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/37842
- DOI
- 10.1039/C5TC01720C
- ISSN
- 2050-7526
- Article Type
- Article
- Citation
- JOURNAL OF MATERIALS CHEMISTRY C, vol. 3, no. 35, page. 9224 - 9232, 2015-08
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