Investigation of metal contacts for silicon solar cells using laser processed 8 μm thick Al foils

The laser processing of thick aluminum foil (8 μm) has the potential of providing low resistance metal contacts and reducing the fabrication cost for silicon solar cells. A high-power nanosecond pulsed laser with wavelength of 1064 nm was used in combination with a soda-lime glass substrate to make electrical contacts between aluminum foil and silicon where the glass substrates allowed flattening of the foil for laser processing. The initial demonstration was performed by passing a laser beam through glass and irradiating an aluminum foil to contact p-type silicon through a passivation layer of SiOx. Cross-section morphologies of resultant line contacts were investigated. A specific contact resistivity as low as 1.8 mΩ-cm2 was achieved based on measurements by the Transmission Line Method (TLM). A non-vacuum laser assisted rear metallization process based on cost-effective aluminum foil is feasible for silicon solar cell fabrication.