Self-aligned Cu electroplating of the front surface contact on silicon solar cells

Abstract

Industrially-manufactured crystalline silicon (Si) solar cell contacts are based on screen printing of metal pastes silver (Ag) on the front and aluminum (Al) on the back surface, respectively. Screen printed contacts are inherently inefficient and requires high processing temperatures. Alternate metal contacts for silicon solar cells based on electroplating have been investigated. Metallization schemes based on electroless nickel (Ni) and copper (Cu) electroplating offers a simple, costeffective, low processing temperature and reduced contact resistivity option for silicon solar cells. An ohmic contact to ndoped emitter is formed with an electroless Ni deposition process using self-aligned approach. This allows Cu electroplating only on the Ni seed layer, which eliminates the need of additional processing for protecting active device regions. This metallization scheme exhibited higher performance with higher fill factors and open-circuit voltages in contrast with screen-printed solar cells.