Aluminum local back surface field solar cells with inkjet-opened rear dielectric films

The rear surface of industrial p-type Cz wafers with a homogeneous n⁺ diffused emitter on the front was coated with a dielectric stack consisting of AlO_x (40 nm) and a SiN_x capping layer (100 nm), all deposited by plasma-enhanced chemical vapor deposition. Subsequently, the dielectric stack was locally opened using either laser ablation or inkjet printing. Three printing conditions with various pitch distances and number of inkjet printed layers were used and their impact on the solar cell efficiency investigated. A champion solar cell efficiency of 18.0% was achieved for a 125-mm pseudo-square, screen-printed Al-LBSF cell with inkjet-opened rear dielectric layer, while reference Al-LBSF cells with laser-opened rear dielectric layer achieved 17.6% champion cell efficiency.