Charusheela Ramanan

Northwestern University
2190 Campus Drive
Evanston, IL 60208-3113

E-mail:
c-ramanan[at]northwestern.edu

Phone: (847) 491-4420

Office: Ryan Hall 2022

Education

Joint Student with Marks Group

2006-Present
Northwestern University, Dept. of Chemistry
PhD Candidate (expected 2011)

2001-2005
University of California, Berkeley
B.S. Chemistry

Research Description

My research focuses on the study of perylene 3,4:9.10-bis(dicarboximide) derivatives as acceptors in organic photovoltaic devices. While these chromophores have been of interest for device application for years, their performance in solar cells has been very limited. The tendency of the perylene core to aggregate through π-π interactions has traditionally been considered a potential advantage due to the increased charge mobility through this stacking channel. However, it has also been proposed that this tendency to aggregate results in device performance losses due to the formation of undesirable morphologies as well as the disruption of necessary photophysical processes within the active layer.

Figure 1: PDI small molecule acceptors with disrupted core aggregation

To further understand and address this issue, I am developing functionalized PDI derivatives with variable stacking motifs and studying photoinduced charge separation in film with donor materials, as well as full device performance.

The first scheme involves tuning the aggregation of PDI small molecules by surrounding the core with large substituents. The second scheme focuses on larger macromolecular systems that utilize PDI aggregation to create an intermolecular network for omnidirectional charge transport

Scheme 1 – PDI small molecule acceptors with disrupted core

Scheme 2 – Macromolecular systems for omnidirectional charge transport

Publications

Bullock, J. E.; Vagnini, M. T.; Ramanan, C.; Co, D. T.; Wilson, T. M.; Dicke, J. W.; Marks, T. J.; Wasielewski, M. R. "Photophysics and Redox Properties of Rylene Imide and Diimide Dyes Alkylated Ortho to the Imide Groups" J Phys Chem B, 2010, 114, 1794.

Hains, A. W.; Ramanan, C.; Irwin, M. D.; Liu, J.; Wasielewski, M. R.; Marks, T. J. "Designed Bithiophene-Based Interfacial Layer for High-Efficiency Bulk-Heterojunction Organic Photovoltaic Cells. Importance of Interfacial Energy Level Matching" Acs Appl Mater Inter, 2010, 2, 175.