Speaker: Michael Graetzel, Professor

Affiliation: Physical Chemistry, Ecole Polytechnique Fédérale de Lausanne

Location: CNSI Auditorium

Molecular Photovoltaics and Perovskite Solar Cells

Molecular photovoltaics have emerged as credible contenders to conventional p-n junction photovoltaics. Mimicking light harvesting and charge carrier generation in natural photosynthesis, dye sensitized solar cells (DSCs) were the first to use three-dimensional nanocrystalline junctions for solar electricity production, reaching currently a power conversion efficiency (PCE) of over 14% in standard air mass 1.5 sunlight. Remarkably their PCE attains 30% in ambient light, matching the performance of the best conventional photovoltaic GaAs. By now, large-scale DSC production and commercial sales have been launched on the multi-megawatt scale for application in building integrated PV and light-weight flexible power sources. Recently, the DSC has engendered perovskite solar cells (PSCs) whose meterioric rise has stunned the scientific community. These employ metal halide perovskite of the general composition ABX3 as light harvesters, where A stands for methylammonium, formamidinium or caesium, B denotes lead or tin and X iodide or bromide. Certified power conversion efficiencies (PCEs) attain now 22.7 %, exceeding the PCE of polycrystalline silicon solar cells. These show intense electro-luminesence and high photovoltages rendering perovskite-based photosystem very attractive for applications in tandem cells and for the generation of fuels from sunlight. Recently impressive progress in attaining long term operational stability of PSCs has been achieved and will be discussed.

About the Speaker

Michael Graetzel, Ph.D., is Professor of Physical Chemistry at the Ecole Polytechnique Fédérale de Lausanne (EPFL), and he directs the EPFL Laboratory of Photonics and Interfaces. He pioneered research on energy and electron transfer reactions in mesoscopic systems and their use to generate electricity and fuels from sunlight. He invented the dye-sensitized solar cells (DSC), which are meanwhile commercially produced at the multi-MW-scale and created a number of new applications in particular as lightweight power supplies for portable electronic devices and in photovoltaic glazings. They engendered the field of perovskite solar cells (PSCs), the most exciting break-through in the recent history of photovoltaics. Graetzel received a number of prestigious awards, of which the most recent ones include the RusNANO Prize, the Zewail Prize in Molecular Science, the Global Energy Prize, the Millennium Technology Grand Prize, the Samson Prime Minister’s Prize for Innovation in Alternative Fuels, the Marcel Benoist Prize, the King Faisal International Science Prize, the Einstein World Award of Science and the Balzan Prize. He is a Fellow of several learned societies and holds eleven honorary doctor’s degrees from European and Asian Universities. According to the ISI-Web of Science, his over 1500 publications have received some 240,000 citations with an h-factor of 221 demonstrating the strong impact of his scientific work.