# 07- Porous polymer films with tailored light scattering properties

**Source**: https://www.cs.tum.de/spp1839/projects/2nd-period-2018-2021/07.html
**Parent**: https://www.cs.tum.de/spp1839/projects.html

In the "PROPOLIS" project, we aim at developing
porous polymer films with tailorable light scattering properties. The
porous network is inspired by the scales of brilliant white beetles and
is fabricated using a highly scalable foaming process with supercritical
CO2. Structural disorder is tuned by controlling the pores nucleation
and growth, resulting in adjustable diameter distributions (from
micrometer to nanometer scale), density and distribution of the pores
within the films.

Understanding the
relationship between the optical properties of the developed films
(light scattering and transport mean free path, scattering anisotropy,
relative fraction of forward/backscattered etc.) and the porous network
morphology is a pivotal aspect of our project. This is achieved by
combining spectroscopic measurements and dedicated numerical methods
either based on ray-tracing (Monte Carlo) simulations as well as on the
T-matrix method to account for coherent multiple scattering effects.

The developed porous
polymer layers offer a cost-effective and flexible solution for
different energy-related applications. This is demonstrated by
optimizing the light scattering properties of such films in order to
improve the light conversion efficiency of quantum dots-based light
emitting diodes, the cooling power of passive radiative cooling systems
and light harvesting in thin film solar cells.

## Contributors

Prof. Uli Lemmer

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PD. Hendrik Hoelscher

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Dr. Guillaume Gomard

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Dominik Theobald

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## References

- Pattelli, L., Egel, A., Lemmer, U., & Wiersma, D. S. (2018). Role of packing density and spatial correlations in strongly scattering 3D systems. *Optica*, *5*(9), 1037-1045

## Upcoming events for 2018

Our work will be
presented at the MRS Fall Meeting 2018 (Symposium: EP07: Tailored
Disorder—Novel Materials for Advanced Optics and Photonics) by Donie
Yidenekachew:

1) Oral presentation:
Towards Inkjet Printing of Phase-Separated Nanostructures for Light
Extraction in Organic Light Emitting Diodes

2) Visual presentation:
Tuning Light Scattering by Phase-Separated Nanostructures for Front- and
Rear-Side Light Trapping in Photovoltaics

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