Implementaion of nanoclusters in intermediate reflective layers

Abstract

The photon management plays a crucial role in thin film single junction or tandem silicon solar cells. Light trapping by means of metal nanoparticles (NPs) opens up a wide range of ways to improve solar cell efficiency due to plasmonic- enhanced light scattering at the metal-dielectric interface. In particular, combination of plasmonic light scattering at the interface between the intermediate reflective layer (IRL) and microcrystalline Si in micromorph tandem solar cells can lead to an efficient light trapping of the low energy photons in the microcrystalline silicon. We used a remote Expanding Thermal Plasma (ETP) in combination with magnetron sputtering to deliver metallic NPss with controlled size and density (size range 30–150 nm, below the percolation threshold). The ETP was also used to deposit thin ZnO of about 130 nm, to serve as IRL. In this work copper and silver NPs are implemented in the IRL with the purpose of enhancing forward scattering towards μc-Si:H and backward scattering towards α-Si:H in micromorpho solar cells. The NPs were implemented in two configurations, i.e.-between the substrate and IRL and on top of the IRL deposited on glass substrate. Surface morphology and metallic nanoparticle size are characterized by means of AFM, SEM, TEM, and correlated with surface plasmon effects. Characteristic haze up to 35% was measured in the range of 400–2500 nm showing high scattering efficiency of the wavelength above 600 nm. The scattering efficiency shifts to the higher wavelength range along with an increase in peak amplitude as the particle size increases.