Novel hole selective CrOx contact for dopant-free back contact silicon solar cells

The dopant-free back contact solar cells are demonstrated based on hole selective contact material, chromium trioxide (CrOx, x < 3) with a low melting point for high stability and high performance. In this contribution, CrOx is first applied in silicon based solar cell as the emitter. Integrating 5 nm CrOx and 2 nm LiFx into solar cell as the emitter and the back surface filed, resulted in a device efficiency of 13.6%. For further improvement, the back contact solar cell reaching an efficiency of 15.8% was fabricated, by implementing the multilayer films of CrOx (5 nm)/Au (4 nm)/ CrOx (5 nm) as the emitter. The formation of Cr(OH)3 in ambient condition, resulted in a lower work function (4.8 eV) of the CrOx film. Furthermore, the multilayer back contact solar cell demonstrated a high stability due to CrOx covered with 500 nm Ag, when stored in ambient air longer than 170 days.