This tutorial is on experimental methods relevant for the investigation of materials with applications in chromogenic devices. The focus in this context will be on methods probing the composition structure and excitations of materials using scattering methods and spectroscopic techniques.

8:30 AM – 9:00 AM Introduction

9:00 AM – 10:30 AM
Part I: Max Wolff
The Compositional of Chromogenic Materials

The performance and optical response of chromogenic materials depends critically on their composition and often on the presence of light elements. Specific examples in this context are transition metal hydrides or oxy-hydrides like Y or Gd. Ion beam methods offer a unique tool in this context to determine the exact composition of materials and in particular thin films in detail and non-destructively. In this lecture the principles of ion beam analysis, namely Rutherford backscattering, elastic recoil detection and nuclear reaction analysis will be outlined. The applicability of the methods will be exemplified on the example of yttrium oxy-hydrides, where by the combination of the different methods a full coherent compositional analysis was performed.

10:30 AM -11:00 AM BREAK

11:00 AM – 12:00 PM
Part II: Max Wolff
Structural Investigation of Chromogenic Materials

The band structure of materials is dictated by the structural arrangements of the atoms in the unit cell and defines the optical properties. As a result detailed structural analysis of chromogenic materials is a key to allow tailoring of the performance. Electrons, x-rays and neutron diffraction can provide this information. In this lecture a brief introduction into diffraction methods will be given. The methods will be exemplified on specific examples analyzing the connection between phase transitions, lattice expansion and optical properties.

12:00 PM – 1:30 PM BREAK

1:30 PM – 2:30 PM
Part III: Max Wolff
Systems and Engineering Aspects including Safety and Reliability

Chromogenic materials are optical active and as a result often used as coatings or in the form of thin films deposited on a substrate. In this lecture scattering methods particularly adapted for thin film and surface studies will be introduced. These methods foot on the investigation of scattering angles close to the critical angle of total external reflection using x-rays or neutrons. Examples on the in-situvstudy of optical and thin film studies will be presented.

2:30 PM – 3:00 PM BREAK

3:00 PM – 4:00 PM
Part IV: José Montero
Spectrally Selective Coatings

Spectrally selective coatings and chromogenic films are used in windows to control the solar energy that comes into the building and to provide extra thermal insulation. In this lecture, the basics of spectral selectivity will be discussed. This include: the solar spectrum and the eye sensitivity, optical band gap and spectral selectivity, coexistence of transparency and conductivity, degenerate wide-bandgap thin films, Burstein-Moss effect, Urbach tail and disorder, refractive index, Drude absorption and plasma frequency, light scattering and effective-medium approximations. In addition, the usual methods for the characterization and modelling of the optical properties of spectrally selective coatings will be discussed, with a special focus on ellipsometry, spectrophotometry and the importance of the concepts of luminous transmittance and solar transmittance. Furthermore, the new optical features that arise in nano- and micro-particulate materials and their promising application in smart fenestration will be presented.

4:00 PM – 5:00 PM Closing Remarks and Open Discussion

Instructors

• Max Wolff, Uppsala University
  
• José Montero, Institute for Energy Technique (IFE)