UV-Ozone Oxide for Surface Clean, Passivation, and Tunneling Contact Applications of Silicon Solar Cells

We demonstrate the versatile use of UV-ozone oxide (UVo) in surface cleaning, surface passivation, diffused junction passivation, and current tunneling applications of crystalline silicon (c-Si) solar cells. A UV-ozone generated oxide is used as a surface clean for random textured c-Si samples and the effectiveness of surface clean is determined by capping with a thin layer of aluminum oxide (AlO _x ). Our developed UVo clean has resulted in a cleaning efficiency almost comparable to that of the benchmarked RCA clean, yielding a saturation current density of 12 fA/cm ² . When planar and textured c-Si samples are capped by a stack of UVo and AlO _x , a UV-ozone growth time of no more than 3 min is found to provide an optimum surface passivation. When tested on phosphorus and boron diffused junctions (with sheet resistance, R _sh of 110–120 $\Omega\!/\!{\scriptstyle\square} $ ), the UVo and AlO _x stack resulted in a J ₀ of 11 fA/cm ² or lower. The high-resolution transmission electron microscope imaging revealed that UVo structure is stable upon annealing for passivation activation. Last, when applied as a tunneling contact, the UVo realizes a contact resistivity ( ρ_c ) of ∼1 mΩ-cm ² and ∼20 mΩ-cm ² for boron and phosphorus doped metal-insulator-semiconductor contact structures, respectively, with moderately doped diffusions.