Inclusion of GaAs Heterojunction Window Layers on the Emitters of Microtextured Si Solar Cells

We investigated the inclusion of GaAs heterojunction window layers on Si solar cell emitters. The n-type GaAs thin film was deposited on microtextured pn junction Si solar cells for 3 and 30 sec using an electron beam evaporator to form the window layers. The solar cells were fabricated with standard cell processes, including microtexturing the surface, n-type emitter diffusion, GaAs thin film deposition, SiN _x anti-reflection coating and metallization with Ag and Al pastes by screen printing, and finally co-firing and edge isolation processes. The fabricated cells showed a reduced photoreflectance at the spectral range of 400∼800 nm, indicating the optical window effect of GaAs. Furthermore, the optical window can improve the cell conversion efficiency. For the GaAs thin film deposited for 3 sec, cell conversion efficiency improved to 16.92% when compared to a reference cell of 16.74%.