Low-cost plasma immersion ion implantation doping for Interdigitated back passivated contact (IBPC) solar cells

Abstract

We present progress to develop low-cost interdigitated back contact solar cells with pc-Si/SiO2/c-Si passivated contacts formed by plasma immersion ion implantation (PIII). PIII is a lower-cost implantation technique than traditional beam line implantation due to its simpler design, lower operating costs, and ability to run high doses (1E14–1E18 cm−2) at low ion energies (20eV–10keV). These benefits make PIII ideal for high throughput production of patterned passivated contacts, where high-dose, low-energy implantations are made into thin (20–200nm) a-Si layers instead of into the wafer itself. For this work symmetric passivated contact test structures (~100nm thick) grown on n-Cz wafers with pH3 PIII doping gave implied open circuit voltage (iVoc) values of 730mV with Jo values of 2fA/cm2. Samples doped with B2H6 gave iVoc values of 690mV and Jo values of 24fA/cm2, outperforming BF3 doping, which gave iVoc values in the 660–680mV range. Samples were further characterized by SIMS, photoluminescence, TEM, EELS, and post-metallization TLM to reveal micro- and macro-scopic structural, chemical and electrical information.