Inverse opals are nano-structures with three dimensional periodicity, which
confers them a control on the light passing through them. The light can be forbidden
to exist within the structure, giving a physical e ect known as optical band-gap,
which is the analogue of the electronic band-gap observed in semiconductors materials.
For these reasons, these structures are part of a larger class of materials,
called photonic crystals. In addition of the light control, inverse-opal structures
o er a large surface area in an organised way, which makes them advantageous
in specialised devices. Due to the complex fabrication process needed to produce
high-quality inverse opal, only a limited amount of work has been done on their
integration in optoelectronic devices. To complete this gap, this thesis aims to produce
inverse opals made from new materials, for use in optoelectronic devices, such
as solar cells and light emitting diodes.
This thesis is divided in 5 results chapters, as described hereafter. Chapter
3 details the fabrication procedures developed to obtain reproducible inverse opals on
a large scale. The structures are made by using an opal template made of polystyrene
nanoparticles, which shows excellent optical properties, which is then in ltrated with
precursors. In chapter 4, a new concept for solar cell architecture is proposed, with
the use of a
uorine tin oxide inverse opal as a three dimensional electrode, to
optimise the charge collection, and lead halide perovskite as an absorbing layer.
The in ltration of lead halide perovskite inside the inverse opal is very challenging
due to the complex crystallisation of this material. A partial in ltration can be
obtained with an optimised deposition method, and working solar cells have been
made with this architecture.
Work to prepare large-scale crack-free inverse opal made of
uorine tin
oxide is described chapter 5. Due to the high reactivity of the precursors used to
make this material, a di erent approach of in ltration is made, with the synthesis
and use of nano-crystals of this material. The structures made in this section show
a great decrease in the amount of cracks, as well as very good periodicity. In chapter
6, a novel architecture for a light-emitting diode is proposed, which makes use of
the optical properties of the inverse opal to sharpen the emission spectrum. A
method to homogeneously coat the inverse opal by sol-gel has been optimised, and a
standard OLED has been made, to con rm the choice of materials. The structures
are simulated with a nite-di erence-time-domain (FDTD) code, in order to study
their optical properties. To nish, the work in chapter 7 reports the creation of very
large scale structures of 15x15cm2, which show good optical effects.