We demonstrate that the passivation quality of TiO2 electron-selective contacts can be improved by Ta doping. By using atomic layer deposition, 3.5-nm-thick, undoped TiO2 films and Ta-doped TiO2 (TiO2:Ta) films with Ta concentrations of 1.5, 2.8, and 5.5 at.% were formed on n-type crystalline silicon substrates with chemical SiO2 layers. After annealing at 130 °C, the effective minority-carrier lifetime (τeff) of the TiO2:Ta-passivated samples were significantly higher than that of the undoped-TiO2-passivated samples, and the highest τeff was obtained at a relatively low Ta-doping concentration of 1.5 at.%. These indicate that moderate Ta doping improves the passivation quality of TiO2 thin films.
- Carrier-selective contact
- Crystalline silicon solar cell
- Titanium oxide