Sustainable Energy Materials

Enabling the energy transition
Climate change is the greatest challenge facing society in the coming decades. There is an urgent need to transition from a world fueled by fossil energy to one powered by the sun. A future sustainable society must convert sunlight much more efficiently to electricity, chemicals, heat and light where and when they are needed. A key unifying theme in all these solar energy conversion processes is that they require exquisite control over both light and matter at nanometer length scales and ultrafast (fs-ns) time scales.

Sustainable Energy Materials
The overarching goal of the Sustainable Energy Materials theme is to use fundamental insights in (nano)photonics and (nano)materials to efficiently convert sunlight to electricity, chemicals, fuels, light and heat. We have the ambition to design and predict where energy flows and how it is converted in artificial photosystems to these different types of useful products. The AMOLF research program in Sustainable Energy Materials brings researchers from different disciplines together to approach the limits of conversion efficiency between different types of energy by controlling materials at the nanoscale. This can translate to completely new material properties and device functionalities, ranging from self-optimizing tandem solar cells to programmable and reconfigurable catalysts that enable totally new designs for light-driven chemical reactors.

Our research questions
We explore how manipulating light, charge and heat in space, time and propagation direction can lead to new energy conversion possibilities. We aim to understand the fundamental mechanisms underlying energetic and material transformations to provide higher efficiency, better stability and new functionality in solar cells, light-emitting diodes and chemical (photo, electro) catalysts.

Our key questions divide in two pillars:

Light to electricity (and back). The most mature and efficient solar energy conversion technology – photovoltaics (PV) – has already benefited from the extensive research developments in controlling light and materials over the last decades, but is still limited to commercial efficiencies of 20-25%, far below the 35-40% that is challenging but feasible and necessary to enable widespread use of solar electricity in society. Completely new materials science is required to go beyond the simple, single-junction silicon solar cells dominating the market today. Within PV some of the most exciting ongoing activities include: ultrahigh-efficiency tandem cells and contacts, solar foils made from halide perovskites and ultrathin Si, novel designs for luminescent solar concentrators, electrochemical III-V growth, radiative cooling of solar cells, and singlet fission layers to strongly enhance silicon PV efficiency. Following from reciprocity, a perfect solar cell is also a perfect light-emitting diode (LED) and thus many of the nanophotonic and material advances in PV can also be leveraged for improved LEDs. In the future, we dream about adaptive PV that can self-tune its absorption to optimize performance depending on the incident spectrum or to switch between a transparent window, a power generating shade and a large-area light source.

Light-driven chemistry. Solar energy conversion to chemicals and fuels is still in its infancy with essentially no commercial market yet. However, over the last decade it has become clear that light-driven chemistry offers completely new possibilities compared to standard thermal chemistry. Using light instead of heat can change the activity and selectivity of catalysts, can lead to completely new products not seen thermally and even in the case of photothermal driving allows for much more localized heating and cooling (in both space and time). It is possible now to change the product a catalyst produces by slightly altering the color of the light source or change the free energy landscape of a reaction by tuning its optical environment (even in the dark). Light pulses can alter the shape and defects of catalyst nanoparticles, which are known to be crucial for chemical reactivity. This opens up the prospect of programmable and reconfigurable chemical activity and selectivity. Despite these numerous exciting possibilities, there is still relatively little mechanistic understanding of light-driven chemistry, which provides a barrier to technological exploitation. We aim to use light to provide the necessary energy input for chemical reactions, as a reagent to control the reactions and as a spectroscopic tool to follow the molecular transformations and discover the underlying reaction mechanism. In the future we dream about materials that can learn a desired function by training with an optical stimulus, light pulses that drive molecules through a free energy landscape in a programmable manner and systems that self-assemble into a desired and self-optimized energy conversion structure.