Michael Grätzel created the field of molecular photovoltaics, being the first to conceive and realize mesoscopic photo-systems based on molecular light harvesters that by now can rival and even exceed the performance of conventional solar cells. He is credited with moving the photovoltaic field beyond the principle of light absorption via diodes to the molecular level. His revolutionary cell design presented a new paradigm since it features a three-dimensional mesoscopic junction , in contrast to the planar p-n architecture used in conventional solar cells. The prototype of this new photovoltaic family is the dye-sensitized solar cell (DSC), also referred to as “Grätzel cell”, which employs dye molecules, pigments or quantum dots as light harvesters These are surface-bound on a support formed by an array of colloidal nanocrystals of wide band gap semiconductor, such as TiO2 or SnO2 as key electron capturing substrate, permitting the realization of very high efficiency photovoltaic thin layer solar cells DSCs are meanwhile industrially fabricated for electricity production, glazing and battery replacements in electronic devices. Furthermore, he played a pivotal role in the recent development of perovskite solar cells (PSCs) that directly emerged from the DSC. Their meteoric rise to reach a solar to electric power conversion efficiency of over 25 % in 2019 has attracted wide research interest with over 10’000 papers being published on the subject over the last 7 years. Graetzel is also a leader in the field of fuel generation by sunlight, which is a key technology to provide future renewable energy sources that can be stored. His group uses tandems of two photosystems to split water into hydrogen and oxygen and reduce carbon dioxide by visible light. Graetzel’s 1645 publications have received some 284’000 citations and his h-index is 243 (Web of Science, September 2019). A recent ranking issued by Stanford University places Graetzel in the first position on a list of 100,000 top scientists across all fields.
The main focus of research at LPI is on photosystems that generate electric power or fuels from sunlight. The inverse process of producing light from electricity in organic light emitting diodes (OLEDS) and the storage of electricity in batteries is also being investigated. The majority of devices examined at LPI employs mesoscopic structures with nanometer-sized features as a key substrate element. In fact, it was the Grätzel group at LPI that pioneered the use of such mesoscopic architectures for the solar production of electricity and fuels. The choice of mesoscopic oxides is supported by our extensive studies of photoinduced electron- and energy-transfer processes of nanocrystalline systems of various kinds. The advantages of using mesoscopic photosystems as solar light harvesters are manifold. Advances in our understanding on how to control/manipulate interfacial charge transfer enables to design efficient photochemical systems that effect overall conversion of solar energy to electric power, as in solar cells or solar fuels, such as H2 from photoelectrochemical water splitting and reduction of CO2 to CO or even C2 products including C2H4 and C2H5OH. Currently, LPI pursues active research in the following three key areas: (1) dye-sensitized solar cells, (2) hybrid perovskites, and (3) solar fuels.