Abstract :
The functional requirements of the component films of a solar thin-film photovoltaic/thermal panel were considered. Particular
emphasis was placed on the new functions, that each layer is required to perform, in addition to their pre-existing functions. The
cut-off wavelength of the window layer, required for solar selectivity, can be achieved with charge carrier concentrations typical of photovoltaic
devices, and thus does not compromise electrical efficiency. The upper (semiconductor) absorber layer has a sufficiently high
thermal conductivity that there is negligible temperature difference across the film, and thus negligible loss in thermal performance.
The lower (cermet) absorber layer can be fabricated with a high ceramic content, to maintain high solar selectivity, without significant
increase in electrical resistance. A thin layer of molybdenum-based cermet at the top of this layer can provide an Ohmic contact to the
upper absorber layer. A layer of aluminium nitride between the metal substrate and the back metal contact can provide electrical isolation
to avoid short-circuiting of series-connected cells, while maintaining a thermal path to the metal substrate and heat extraction
systems. Potential problems of differential contraction of heated films and substrates were identified, with a recommendation that fabrication
processes, which avoid heating, are preferable.
2009 Elsevier Ltd. All rights reserved
Keywords :
Thin film , Photovoltaic , Thermal , Selective , Absorber