Collaborators: Prof. Barry Bruce, Department of Biology, University of Tennessee Knoxville; Prof. Shuguang Zhang, Biomedical Engineering, MIT.

Abstract:

Millions of years of evolutionary adaptation have optimized the molecular circuitry within nanoscale biosystems such as photosynthetic complexes. At present, comparable molecular circuits cannot be fabricated by any artificial technique. In a typical photosynthetic complex such as that found in spinach or a purple bacterium, absorbed photons are harvested within 100 ps of the absorption of a photon with an overall quantum yield of 98%.1 Photovoltages of up to 1.1 V are generated across the complex and the power conversion efficiency is expected to match or exceed the best Si photovoltaic devices, which in practice possess power conversion efficiencies of < 26%.

In prior work, this team (Bruce, Baldo and Zhang) has developed a unique technology for exploiting nanosystems at the bioscale. We have integrated photosynthetic protein complexes with amorphous organic semiconductors and used this technology to fabricate perhaps the first solid-state solar cell incorporating photosynthetic complexes. Here we propose to fully exploit solid-state integration of photosynthetic structures by developing for photovoltaic devices and as a new tool for the study of charge and energy transfer in biological protein-molecular complexes.

See our latest results.

Broader Impact Criteria

• Cheap renewable energy. Conventional inorganic solar cells remain costly and energy intensive to manufacture. Arguably this has limited the impact of photovoltaic devices to much less than 1% of the world-wide supply of energy. It is desirable to develop flexible and lightweight solar cells that perform competitively with inorganic semiconductor cells, but are inexpensive and may be processed like a polymer. Significant enhancements in renewable energy generation may result from harnessing the molecular circuitry within photosynthetic protein complexes.
• Stabilization techniques for transmembrane protein complexes may aid in the study and understanding of these vital biological structures. It is estimated that membrane proteins comprise 20-30% of all cellular proteins, yet few are understood and only a handful of high-resolution structures have been obtained.2 New techniques for stabilizing membrane complexes may allow their organization into regular arrays, opening new avenues to their biochemical study, crystallization and integration into nanodevices.2
• A multi-tiered education strategy targeting graduate students, undergraduate students and middle school students is included in this program. The focus is the training of graduate students, directly in the laboratory environment and through a variety of graduate-level courses. In addition, practical experience is offered, with special emphasis on minority students, to undergraduates, and middle school students and their teachers, via an educational outreach program that introduces middle school students to photosynthetic protein complexes.

See a summary of our outreach efforts.