Understanding and controlling morphology evolution via DIO plasticization in PffBT4T-2OD/PC₇₁BM devices

• Type: Article in International Scientific Journal
• Date: 2017

Authors

Zhang, YW (Author) Other; Parnell, AJ (Author) Other; Pontecchiani, F (Author) Other; Cooper, JFK (Author) Other; Thompson, RL (Author) Other; Jones, RAL (Author) Other; King, SM (Author) Other; Lidzey, DG (Author) Other; Bernardo, G (Author) FEUP

Journal

Title: Scientific Reports

Vol. 7

ISSN: 2045-2322

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 53 Citations

Other information

Authenticus ID: P-011-YFM

DOI: 10.1038/srep44269

Abstract (EN): <jats:title>Abstract</jats:title><jats:p>We demonstrate that the inclusion of a small amount of the co-solvent 1,8-diiodooctane in the preparation of a bulk-heterojunction photovoltaic device increases its power conversion efficiency by 20%, through a mechanism of transient plasticisation. We follow the removal of 1,8-diiodooctane directly after spin-coating using ellipsometry and ion beam analysis, while using small angle neutron scattering to characterise the morphological nanostructure evolution of the film. In PffBT4T-2OD/PC<jats:sub>71</jats:sub>BM devices, the power conversion efficiency increases from 7.2% to above 8.7% as a result of the coarsening of the phase domains. This coarsening process is assisted by thermal annealing and the slow evaporation of 1,8-diiodooctane, which we suggest, acts as a plasticiser to promote molecular mobility. Our results show that 1,8-diiodooctane can be completely removed from the film by a thermal annealing process at temperatures ¿100¿°C and that there is an interplay between the evaporation rate of 1,8-diiodooctane and the rate of domain coarsening in the plasticized film which helps elucidate the mechanism by which additives improve device efficiency.</jats:p>

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 12