EAGER - Nanostructured Plasmonic Contacts for Enhanced Efficiency in Organic Photovoltaic Cells

0946723

Holmes

Summary

The development of low-cost renewable and sustainable energy sources is the foremost challenge facing humanity. While solar energy conversion is currently too costly to compete with fossil fuel sources, organic photovoltaic cells (OPVs) will redefine this energy balance. OPVs can be processed using high-throughput methods, and have demonstrated efficiencies >6%. The proposed research outlines a new approach to overcome the exciton diffusion bottleneck that limits OPV absorption efficiency.

Intellectual Merit: Thin film OPVs based on graded donor-acceptor heterojunctions (GHJs) will be incorporated into plasmonic nanocavity arrays to increase the absorption and power conversion efficiencies of these devices. The use of a plasmonic nanocavity permits subwavelength confinement and resonant enhancement of the optical field. The combination of a GHJ OPV with a plasmonic nanocavity array has the potential to be transformative by enabling a high level of tunability and control over the film microstructure and internal optical field distribution to realize high efficiency. A new architecture combining optical field enhancement from a plasmonic nanocavity array is introduced to overcome the exciton bottleneck and maximize absorption in OPVs. This enhancement is attractive since it is long range, enhancing absorption throughout the organic active layers. The use of a nanocavity permits the spectral response of the enhancement to be tuned to overlap with active material absorption. The OPVs proposed in this work will utilize GHJs to realize exciton dissociation. The novel use of a GHJ is attractive since it balances the need for efficient exciton diffusion (large interface area) with efficient charge collection (graded pathways for transport). The growth of GHJs is tunable, enabling a range of compositions through which to correlate morphology, exciton/charge transport, and performance.

Broader Impact: Graduate students associated with this project will acquire an interdisciplinary spectrum of knowledge ranging from nanofabrication and plasmonics, to molecular photophysics and OPV performance. Students will also be educated in renewable energy, understanding the position of OPVs in the broader energy landscape. Discussions of photovoltaics and plasmonics are already being integrated into various undergraduate and graduate courses taught by the PIs. Undergraduate research opportunities will be enhanced through continuing relationships with the University of Minnesota UROP program and the National Science Foundation REU program. These activities are complemented by plans to disseminate results from the proposed work to industry via on-campus workshops and an industrial affiliates program.