Search

In this study, titanium dioxide (TiO2) films are prepared using spatial atomic layer deposition (sALD) as an additional compact layer of tin oxide (SnO2) electronic transport layer-based perovskite solar cells. The experimental results show that the deposition of sALD TiO2 films on the fluorine-doped tin oxide substrate improves the haze at mid-long wavelengths, compensating the optical loss caused by the absorption of the TiO2 layer in short-wavelengths. Compared to conventional cells, the insertion of the sALD TiO2 compact layer regardless the thickness shows significantly improved open-circuit voltage, indicating the enhanced hole blocking ability as evidenced by the reduced reverse saturation current. In addition, the change in TiO2 thickness is found to have impacts on short-circuit current, fill factor and hysteresis of the devices. The optimal sALD TiO2 thickness of 10 nm leads to the best cell conversion efficiency of 20.1%, approximately improved by 6% compared to that of the conventional cells. Compared to conventional ALD techniques and other methods, the sALD which does not require vacuum system has the pinhole-free, low-cost, very fast and simple processes, demonstrating the great potential of sALD films for applications in perovskite solar cells.

In this study, spatial atomic layer deposition (sALD) is employed to prepare titanium dioxide (TiO2) thin films by using titanium tetraisopropoxide and water as metal and water precursors, respectively. The post-annealing temperature is varied to investigate its effect on the properties of the TiO2 films. The experimental results show that the sALD TiO2 has a similar deposition rate per cycle to other ALD processes using oxygen plasma or ozone oxidant, implying that the growth is limited by titanium tetraisopropoxide steric hindrance. The structure of the as-deposited sALD TiO2 films is amorphous and changes to polycrystalline anatase at the annealing temperature of 450 °C. All the sALD TiO2 films have a low absorption coefficient at the level of 10−3 cm−1 at wavelengths greater than 500 nm. The annealing temperatures of 550 °C are expected to have a high compactness, evaluated by the refractive index and x-ray photoelectron spectrometer measurements. Finally, the 550 °C-annealed sALD TiO2 film with a thickness of ~8 nm is applied to perovskite solar cells as a compact electron transport layer. The significantly enhanced open-circuit voltage and conversion efficiency demonstrate the great potential of the sALD TiO2 compact layer in perovskite solar cell applications.