Proceedings Article | 13 November 2007
Nikolai Lebedev, Anthony Spano, Scott Trammell, Igor Griva, Stanislav Tsoi, Joel Schnur
KEYWORDS: Electrodes, Proteins, Photovoltaics, Gold, Self-assembled monolayers, Carbon, Solar energy, Quantum efficiency, Solid state electronics, Semiconductors
Construction of efficient devices for light energy conversion, including photo-electronic and photovoltaic (PV) devices,
is a big challenge for the current science and technology that will have important economic consequences. Most of the
modern photovoltaic devices are based on silicon. An innovative approach to the construction of photovoltaic devices is
the utilization of biological systems and principles designed for similar purposes by Nature. Biological electronic
devices, proteins, have extremely high efficiency, precise spatial organization, and are inexpensive in fabrication. They
can be fused with inorganic and organic materials such as conductors, semiconductors, conductive polymers, or quantum
dots. The photosynthetic reaction center protein (RC) is one of the most advanced photo-electronic devices developed by
Nature. It has nearly 100% quantum yield of primary charge separation, an extremely fast operation time (about 10-9 s, or
operation frequency of ~109 Hz), and a very efficient stabilization of separated charges (ratio of charge separation rate to
that of charge recombination is about 104). The charge separation and stabilization takes place in a complex of 7 nm size
and leads to the formation of a local electric field of about 106 V/cm. A coupling of photosynthetic RC to inorganic
electrodes is attractive for the identification of the mechanisms of inter-protein electron transfer (ET) and for the possible
applications in the construction of protein-based innovative photoelectronic and photovoltaic devices. In this
presentation we describe a new type of hybrid bio-inorganic photoelectronic devices based on photosynthetic proteins
and inorganic materials. Using genetically engineered bacterial RCs and specifically synthesized organic linkers, we
were able to construct self-assembled and aligned protein complexes with various metals and semiconductors, including
gold, indium tin oxide (ITO), nanoporous TiO2, highly ordered pyrolytic graphite (HOPG) and carbon nanotube (CNT)
arrays. Our results show that photosynthetic protein-inorganic complexes can operate as highly efficient photo- and
chemo-sensors, optical switches, photorectifieres, or photovoltaic devices.
