Plasmonic effect to boost solar cell efficiency
Photovoltaic (PV), or solar, cells are poised for massive market penetration if efficiency can be increased at reduced costs. Excitation of plasmons in thin-film SCs seems to be a promising way to achieve this. Plasmons are coherent and collective electromagnetic waves formed by oscillations of nearly free electrons at the interface between two materials, typically a metal and a dielectric. Inducing this plasmonic effect around metallic NPs embedded in dielectrics enables enhanced light capture at specific wavelengths, increasing absorption efficiency. Partners on the 'Plasmons generating nanocomposite materials (PGNM) for 3rd generation thin film solar cells' (SOLAMON) project developed tailored NP building blocks for embedding in commercial low-cost silicon substrates to generate a plasmon effect. Embedding was done with a new patented room-temperature deposition process for large NPs. Three classes of thin-film SCs were considered: one suitable for the building-integrated PV (BIPV) market and the other two for smaller-scale consumer products. SOLAMON researchers deposited both small and larger silver (Ag) NPs, demonstrating good process control and reproducibility as well as the ability to induce a plasmonic effect. Promising preliminary experiments were also carried out with large core-shell metallic NPs, the production of which has led to two patent applications. Integrated simulation software was used to determine and compare the optical properties of the three SC types with and without PGNMs. PGNM layers were successfully incorporated into all three, with preliminary tests pointing the way to further optimisations. In particular, the use of large core-shell metallic NPs is likely to overcome certain technical difficulties seen during the simulation and testing phases. Generation I SCs are in use and Generation II, thin-film SCs are even more competitive in terms of price, but lacking in desired conversion efficiency. SOLAMON technology is pointing the way to a unique opportunity to increase efficiency using embedded NPs capable of inducing plasmon resonance for Generation III thin-film SCs. Reaching goals with continued research will have significant impact on the global energy market.