(6iz) Photoelectrochemical solar energy conversion system : New materials and concepts

Growing energy demand and the anthropogenic climate change, resulting from the use of fossil fuels, drives research both in academia and industries towards identifying a cheap and clean energy source. Solar energy, with its enormous power resource accounting to about 120,000TW far exceeds the global energy demand (13-15TW) and an efficient conversion of solar photon energy to electricity/fuels can potentially alleviate the energy problem. In addition to the efficient conversion, their cost factor plays an important role in determining their deployment on a TW scale. Third generation molecular photovoltaics including dye-sensitized photoelectrochemical devices because of simple device fabrication techniques and the use of low cost device materials, offer a significant potential for the construction of cheap solar cells /solar fuel systems.

            During my PhD, I worked on understanding the photogenerated electron loss mechanisms and finding ways to rectify the losses, in such a photoelectrochemical system. The parasitic electron recombination at the semiconductor-electrolyte interface reduces the efficiency of the solar conversion. I extensively investigated the carrier losses at this interface and developed quantum tunneling layers to block the unwanted reaction, for high efficiency dye-sensitized solar cells. One of the key research outcome is, we redefined a key theory of electron recombination. In the photoelectrochemical solar cell community, there existed a common (mis)conception that 'any insulating oxide that is sufficiently thin to allow electron tunneling, should block the electron recombination at the semiconductor-electrolyte interface'. However, we discovered that only certain insulating oxides can block the charge-carrier recombination while other oxides don't. By a systematic and thorough investigation, we developed a set of criteria to select an efficient  tunneling layer for high efficiency solar cells. This work, in addition to the semiconductor-electrolyte interface, has been extended to the dye/perovskite semiconductor-solid state hole conducting devices and the criteria we developed, is also found to be valid for the latter systems. With the research background in the photoelectrochemistry, I moved to UC Berkeley for a postdoctoral research  to develop photoconducting metal-organic frameworks (MOFs) that can act as an absorber and charge-transporter in solar cells/solar fuels systems. The possibility of combining wide range of metal cations and linkers make MOFs an interesting candidate for tuning the optical and electronic properties. Currently I am investigating the charge transport and photophysical properties of porphyrin and thiol based MOFs for their potential application in solar energy conversion.

            In future, I want to be a part of the greatest scientific community that explores the interdisciplinary aspects of science in solving the energy crisis. As an independent faculty member, I am interested in investigating new materials and device concepts for an effective solar fuel generation using photoelectrochemical systems, that uses three abundant resources on earth, namely, water, carbon dioxide and sunlight. Two key chemical reactions that I specifically would like to explore are carbon dioxide reduction to hydrocarbons and water splitting to hydrogen fuel. Considering the pitfalls/limitations in the existing technologies for the solar fuel generation, I developed new device concepts and material synthesis pathways by blending novel concepts in ferroelectrics, semiconductor electrochemistry, photochemistry, catalysis, coordination chemistry and material science, that will bring in new dimension to energy sciences.  In the AIChE poster, I will present my new ideas that can potentially revolutionize the field of solar fuels.