IMPACT OF METALLIZATION TECHNIQUES ON SURFACE PASSIVATION OF HIGH EFFICIENCY CRYSTALLINE SILICON SOLAR CELLS

摘要

Most of the high-efficiency c-Si solar cells are based on dielectric films that electrically passivate c-Si surface and must keep their passivation properties after metal deposition on top of them. This work studies the impact of three different aluminum Physical Vapor Deposition (PVD) methods (thermal, e-beam, sputtering) on the c-Si surface passivation provided by SiO_2 and Al_2O_3 films. Effective surface recombination velocity is measured before and after metal deposition. Results show that e-beam and sputtering techniques degrade surface passivation while thermal evaporation has no impact. Surface passivation can be recovered and even improved by means of an annealing with the aluminum film on top of the dielectric leading to the so-called alnealing. Additionally, after this alnealing Capacitance-Voltage measurements and lifetime spectroscopy analysis suggest a strong dependence of fixed charge density for SiO_2 films on the metal deposition technique that helps in c-Si surface passivation.