Several emerging photovoltaic (PV) applications are currently requiring the development and implementation of transparent conductive materials (TCMs) beyond their traditional use as front electrodes in solar cells, and not only letting the light reaching the junction. Next generation PV devices with higher functionalities as transparent/semitransparent devices for glass-based building integration elements and windows require the integration of TCMs at several levels of the device architecture, with functions as charge transport or even light absorber layers. This is also required for advanced device architectures aiming towards improving the device efficiency as bifacial cells and tandem/multijunction concepts. The TCMs family includes thus electrodes, selective contacts, and even absorber layers presenting a certain degree of transparency (defined by a wide bandgap).

The transparent conductive oxides (TCOs) are the most common TCMs encountered in literature, thanks to their high electrical conductivity and light transmittance, and are often used as high-performance n-type conductors in a plethora of transparent devices (LEDs, gas sensors, solar cell, etc). Less is found regarding p-type conductors, even if recently Cu-based materials (oxides and chalcogenides) have gained interest in the field, especially thinking in their integration as interlayer electrodes in tandem devices. Another example of TCMs for PV relies in the selective contacts, generally based on metallic oxides/chalcogenides, exploiting kinetics at the interfaces with the absorber, establishing different conductivities for electrons and holes in different regions of the device, thus creating effective separation and selective transport. Finally, wide bandgap absorbers, also respond to the criteria of (semi-) transparent conductive material, thus completing the TCMs family.

After making a brief review of the most common uses of TCMs for PV applications, summarizing their main potential and challenges, a special focus will be put on their integration with existing thin film technologies, in particular with kesterite. The main results of the optimization of the replacement of the Mo back contact (commonly used in the kesterite technology) by TCOs will be presented. In particular the required functionalization (involving TCMs as interlayers improving the valence band alignment) of the TCOs for several anionic compositions of the kesterite absorbers (i.e. bandgaps) will be presented, such as the first results of integration in a tandem structure.