Abstract
Electron transfer and subsequent charge separation across donor-acceptor heterojunctions remain the most important areas of study in the field of third-generation photovoltaics. In this context, it is particularly important to unravel the dynamics of individual ultrafast processes (such as photoinduced electron transfer, carrier trapping and association, and energy transfer and relaxation), which prevail in materials and at their interfaces. In the frame of the National Center of Competence in Research “Molecular Ultrafast Science and Technology,” a research instrument of the Swiss National Science Foundation, several groups active in the field of ultrafast science in Switzerland have applied a number of complementary experimental techniques and computational simulation tools to scrutinize these critical photophysical phenomena. Structural, electronic, and transport properties of the materials and the detailed mechanisms of photoinduced charge separation in dye-sensitized solar cells, conjugated polymer- and small molecule-based organic photovoltaics, and high-efficiency lead halide perovskite solar energy converters have been scrutinized. Results yielded more than thirty research articles, an overview of which is provided here.
Highlights
AND SCOPEVC Author(s) 2017.061503-2 Teuscher et al.Struct
The detailed understanding of ultrafast carrier dynamics brought by experimental measurements and calculations is important on a fundamental point of view, but it provides the essential feedback to the design and selection of materials, morphology, heterostructures, and interfaces that enable improved photovoltaic performance
The present review summarizes the results of this common endeavor, during which established femtosecond laser techniques, such as transient absorption (TAS), time-resolved terahertz (TRTS), and time-resolved photoemission spectroscopies were used, while additional experimental tools, such as time-resolved electroabsorption (TREAS) and picosecond X-ray absorption spectroscopies, for instance, needed to be developed
Summary
Other side, prevents the charge recombination and allows the build-up of a significant photovoltage across the device. These types of solar cells do not depend on a built-in electric field at a p-n junction, but rather rely on prompt electron transfer (ET) at interfaces between materials, which energy levels are closely aligned. They are, commonly referred to as donoracceptor heterojunction (DAH) photovoltaic systems. Generation, thermalisation, trapping, interfacial transfer, and recombination of photoexcited charge carriers, as well as the dynamics of excitonic species, often occur on femtosecond to picosecond timescales. The present review summarizes the results of this common endeavor, during which established femtosecond laser techniques, such as transient absorption (TAS), time-resolved terahertz (TRTS), and time-resolved photoemission spectroscopies were used, while additional experimental tools, such as time-resolved electroabsorption (TREAS) and picosecond X-ray absorption spectroscopies, for instance, needed to be developed
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