Cu metal nanoparticles in transparent electrodes for light harvesting in solar cells

We report on copper nanoparticles produced by laser ablation, in acetone and methanol, from a Cu target using a 1064 nm nanosecond pulsed laser. The morphology, size, structure and chemical composition of the nanoparticles are investigated as a function of the solvent employed. Different analyses confirm the metallic nature of the nanoparticles, without amorphous carbon or copper oxides shells. Then, the nanoparticles are embedded between two transparent electrodes, aluminium-doped zinc oxide (AZO) and zirconium-doped indium oxide (IZrO) as top and bottom layers, respectively. The Glass/IZrObott/Cu nanoparticles/AZOtop structures are synthesized and optimized as plasmonic and conductive structure for photovoltaic applications. Optical properties show a strong dependence on the thermal annealing at 200 °C and type of copper nanoparticles embedded in transparent electrodes. The transparent electrode with the lowest Egap limits the Egap to the whole structure. The best structure shows a mean value of transmittance in the visible-NIR range of ∼79% with an Egap of 3.43 eV and, moreover, it shows diffused transmittance between 2.5 and 6% in VIS-NIR range and a sheet resistance of 79 Ω/sq. The performances of the best structure are tested measuring the internal quantum efficiency of a tandem solar cell, getting values as high as 89%.