Inorganic Thin Film Chalcogenides for Indoor PV Applications

The emerging of indoor photovoltaic (IPV) concepts, drive the necessity to search for absorber materials that fulfil the desired requisites for this specific application, including sustainability, low toxicity, durability, cost, and of course excellent performance under indoor illumination conditions. This last target focused the attention in materials with bandgaps higher than 1.6 eV, that historically has been largely overlooked in the literature. In this context, thin film chalcogenides from simple elemental selenium, up to complex quaternary and pentenary compounds, are potentially excellent candidates for IPV, especially regarding their sustainability and stability. In this presentation, an overview and classification of the most interesting thin film chalcogenide compounds for IPV applications will be presented. The different families of chalcogenides will be reviewed, emphasizing the cationic and anionic compositions that led to the right bandgaps for IPV. The latest results for the different families of materials, including elemental Se, (Sb,Bi)2(S,Se)3, and kesterite ((Ag,Cu)2(Zn,Cd)(Sn,Ge)(S,Se)4) will be thoroughly reviewed, with special focus on the fundamental properties that make these materials ideal for PV, as well as the devices architectures under development. A comparative analysis of all these materials will be performed, including very recent results obtained at the UPC Group, with a discussion on the most relevant conditions to measure and report optoelectronic parameters for this application. Finally, a perspective about the future research directions on all these materials, and the identified strengths and weaknesses will be presented.