Material Challenges for Terawatt Level Deployment of Photovoltaics

In this work several photovoltaic technologies, ranging from silicon to thin films, multi-junction and solar concentrator systems are analyzed. The estimates of the energy production limits are established for each technology, based on available global material reserves. It is shown that many existing technologies, albeit playing an important in the present sub-GW energy production levels, are affected by severe material shortages, preventing their scale-up to the terawatt range. This is the case for thin film solar cells technologies based on CdTe and CIGS where the showstopper is the scarcity of tellurium and indium respectively. Despite the abundance of silicon, crystalline Si solar cells will hardly surpass the few terawatt range as further scale-up will be impeded by the global reserves of silver, commonly used as electrode material. For amorphous silicon and dye sensitized thin film technologies, avoiding the use of ITO transparent conductive oxides (ZnO for a-Si and SnO₂ for dye sensitized cells) should favor access to terawatt levels. For existing III-V concentrator cells, operating under moderate concentration (<200X), one to two terawatt year level can be afforded by simply substituting Ge substrates by more abundant GaAs wafer. The development of reliable epitaxial solar cell lift-off techniques should enable the attainment of multi-Terawatt levels