Ga-doped ZnO rear transparent contact enables high efficiency silicon heterojunction solar cells

Gallium-doped zinc oxide (GZO) thin films under different oxygen flows were deposited by low-damage reactive plasma deposition (RPD) technology and their crystal structures, optical and electrical properties were investigated. We find all the GZO films have good crystallinity with (002) preferred orientation and the crystallinity of GZO films increases with the oxygen flow. In addition, the mobility of the GZO film reaches 10.6 cm2/V·s and the resistivity were minimized to 6.24 × 10−4 Ω cm at 10 sccm oxygen flow. Moreover, the GZO film has an average transmittance of 85.35% in the wavelength range of 390–780 nm at 60 sccm oxygen flow. Finally, the SHJ solar cells based on GZO films at front side or rear side were prepared respectively and the optimized efficiency of 23.65% was achieved for SHJ solar cells when the GZO film was deposited on the rear electrode of the cells. To our knowledge, this is the highest efficiency for GZO-based SHJ solar cells currently, which apparently demonstrates that the low-cost ZnO based material is promising for the mass production of SHJ solar cells.