Charge transfer dynamics in organic‐inorganic hybrid heterostructures ‐ insights by vibrational sum‐frequency generation spectroscopy

Organic‐inorganic heterostructures play a pivotal role in modern electronic and optoelectronic applications including photodetectors, field effect transistors, as well as in solar‐energy conversion such as photoelectrodes of dye‐sensitized solar cells, photoelectrochemical cells, and in organic photovoltaics. To a large extent, the performance of such devices is controlled by charge transfer dynamics at and across (inner) interfaces, e.g., between a wide band gap semiconductor and molecular sensitizers and/or catalysts. Hence, a detailed understanding of the structure‐dynamics‐function relationship of such functional interfaces is necessary to rationalize possible performance limitations of these materials and devices on a molecular level. Vibrational sum‐frequency generation (VSFG) spectroscopy, as an interface‐sensitive spectroscopic technique, allows to obtain chemically specific information from interfaces and combine such chemical insights with ultrafast time resolution, when integrated as a spectroscopic probe into a pump‐probe scheme. Thus, this perspective discusses the advantages and potential of VSFG spectroscopy for investigating interfacial charge transfer dynamics and structural changes at inner interfaces. A critical perspective of the unique spectroscopic view of otherwise inaccessible interfaces is presented, which we hope opens new opportunities for an improved understanding of function‐determining processes in complex materials, and brings together communities who are devoted to designing materials and devices with spectroscopists.