Dynamic glazing systems, i.e. windows capable of controlling incoming solar radiation, can significantly reduce energy consumption for lighting and air conditioning in buildings. However, the widespread use of smart window technologies in buildings is still limited by high costs, high energy consumption, long payback periods, slow device response times or lack of operational control. This project focuses on a new device concept, that we call the “photovoltaic spatial light modulator” (or PSLM), a novel dynamic glazing system that has strong potential to bypass some of the bottlenecks that currently limit the integration of smart windows into buildings. PSLM devices are hybrid optically-addressable liquid crystal light modulators that include an organic photovoltaic multilayer as the photosensitive element and offer many potential advantages over other smart window systems. They can operate without an external power supply, their response time is several orders of magnitude smaller than that of most other chromogenic devices, they can be easily controlled by the user, their color in the clear state depends on the organic semiconductor band-gap and can be adjusted by chemical engineering, and the photosensitive organic layers can be solution processed and are therefore compatible with large area devices. The architecture of the PSLM device combines, in an unprecedented way, a twisted nematic liquid crystal layer with an organic donor/acceptor bulk heterojunction to produce a new optically functional system. The optical response of the device results from the photoelectric field generated spontaneously by the bulk heterojunction that modifies the liquid crystal director and alters the device transparency. This very particular device design raises a number of scientific and technical challenges that will be addressed in this project, with the goal to improve the performances and broaden the scope of PSLM devices. We aim to better understand and control the interface between the liquid crystal and organic layers, improve the transparency of the device in the clear state, develop more advanced device structures, and explore ways to make the PSLM sensitive to infrared light while remaining highly transparent in the visible range.
To reach these goals, we will synthesize new electron-donor and electron-acceptor polymers with a near UV photon absorption edge as well as new electron-transporting layers, use uniaxially oriented organic layers that are aligned by an improved mechanical rubbing process, perform in-depth physical studies of the liquid crystal / alignment layer interfaces, investigate the charge carrier dynamics in PSLMs and develop advanced device architectures capable of improving the sensitivity and transparency of devices in the near infrared and visible, respectively.
The project consortium includes teams from N. Leclerc of the Institute of Chemistry and Processes for Energy, Environment and Health (ICPEES) for the polymer synthesis, M. Brinkmann of the Institute Charles Sadron (ICS) for the uniaxial orientation of semiconducting and conducting organic materials, D. Ivanov of the Institute for Material Science of Mulhouse (IS2M) for interface studies, M. Kaczmarek of the University of Southampton for liquid crystal device characterizations and T. Heiser (project coordinator) of the ICUBE laboratory for the device physics. The implementation of the project benefits from the complementary skills of the project partners in polymer chemistry, microstructural analysis of organic materials, thin film processing, charge carrier dynamics in semiconductors, organic solar cells and liquid crystal devices.
Monsieur Thomas Heiser (Laboratoire des sciences de l'Ingénieur, de l'Informatique et de l'Imagerie (UMR 7357))
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
IS2M Institut de Sciences des Matériaux de Mulhouse (IS2M) - UMR 7361
University of Southampton / Department of Physics and Astronomy
ICPEES Institut de Chimie et Procédés pour l'Energie, l'Environnement et la Santé
I.C.S Institut Charles Sadron (UPR 22)
ICube _ UNISTRA Laboratoire des sciences de l'Ingénieur, de l'Informatique et de l'Imagerie (UMR 7357)
Help of the ANR 444,696 euros
Beginning and duration of the scientific project: December 2019 - 42 Months