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Calendar: ALS Calendar
Title: ALS Special Seminar | John Tumbleston
When: 01/30/2013 9:30 AM - 10:30 AM
Description: ALS Special Seminar

Wed, January 30, 2013
9:30 - 10:30
6-2202 Conf Room

Cheng Wang

Presented by:
John Tumbleston
North Carolina State University

Unraveling Structure-Performance Relationships in Plastic Solar Cells at the ALS

The performance of bulk heterojunction (BHJ) polymer/fullerene solar cells has steadily improved over the last decade with power conversion efficiencies now near 10%. Progress has been made mostly through trial and error optimization of materials chemistry and device processing often without a clear link between BHJ morphology and performance. This talk will overview results from soft X-ray microscopy (BL and scattering (BL along with complimentary hard X-ray scattering (BL 7.3.3) that when taken together are able to unravel structure-performance relationships in BHJ solar cells. The soft X-ray scattering techniques in particular allow for domain size, domain purity, and properties of electron donor/acceptor interfaces to be quantitatively determined. In terms of materials chemistry, we show how the performance-boosting synthetic technique of fluorine substitution on the polymer backbone leads to larger and purer BHJ domains with polymer crystallites oriented more strongly face-on the substrate. Fluorine substitution also allows for control of polymer orientation with respect to donor/accepter interfaces, a new morphological property in BHJ solar cells. Also in terms of device processing, we show that solvent choice can have a significant morphological impact which in some cases can lead to drastic performance changes but in others can leave performance relatively unaffected.
Location: 6-2202-CR(20)