The backbone of the current microelectronics industry is components based on silicon semiconductors. However, the perspectives for further developments are limited due to material constraints like non availability for flexible devices, optical opacity and need for high temperature processing. The emerging class of oxide semiconductors is able to overcome many of those restrictions, especially because some of them can be prepared as thin (transparent) films under comparatively moderate conditions.

On the same line, functional oxides, with combination of properties, such as dynamic control of optical transparency and efficient light management, have been of increasing interest over the last years. Such coatings have opened up completely new applications areas such as smart windows, solar cell façades, user-controlled thermochromics and electrochromics, etc., which can contribute significantly to reduce the global energy footprint of buildings and consequently the realization of green buildings. It should be reminded that buildings are responsible for consuming about 40% of the total produced energy, while windows are responsible for the loss of 10-25% of the thermal energy of buildings. A properly designed smart window can control and modulate solar heat and lighting and it is possible, at the same time, to produce and store solar energy.

In this presentation, we shall focus on the efforts we have made to produce n-type and p-type oxide semiconductors. Emphasis will be given on the recent attempts το develop NiO by combinatorial doping so to control its properties as a single coating or by forming heterostructures in 1-D & 3-D architectures for applications like UV-PVs, tandem solar cells, electrochromics, sensing and photocatalysis.