Tantalum (Ta)-doped titanium oxide (TiO₂) thin films are grown by plasma enhanced atomic layer deposition (PEALD), and used as both an electron transport layer and hole blocking compact layer of perovskite solar cells. The metal precursors of tantalum ethoxide and titanium isopropoxide are simultaneously injected into the deposition chamber. The Ta content is controlled by the temperature of the metal precursors. The experimental results show that the Ta incorporation introduces oxygen vacancies defects, accompanied by the reduced crystallinity and optical band gap. The PEALD Ta-doped films show a resistivity three orders of magnitude lower than undoped TiO₂, even at a low Ta content (0.8–0.95 at.%). The ultraviolet photoelectron spectroscopy spectra reveal that Ta incorporation leads to a down shift of valance band and conduction positions, and this is helpful for the applications involving band alignment engineering. Finally, the perovskite solar cell with Ta-doped TiO₂ electron transport layer demonstrates significantly improved fill factor and conversion efficiency as compared to that with the undoped TiO₂ layer.

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.

Plasma-enhanced atomic layer deposition is used to fabricate compact tantalum (Ta)-doped titanium oxide (TiO ₂ ) thin films as electron transport layers (ETLs) and hole blocking layers for perovskite solar cells (PSCs). The effects of Ta-doped TiO ₂ with different annealing temperatures on film structure and electronic properties are researched. The experimental results exhibit that the substitutional Ta-doping into TiO ₂ (Ta content of ~1.5%) increases the stability of crystal structure and passivates the material defects, thereby improving the film quality. The annealed Ta-doped TiO ₂ films have a resistivity of approximately 6.5 $\boldsymbol {\Omega } \cdot $ cm which is three orders of magnitude lower than 3.4 $\times 10^{{3}}\,\, \boldsymbol {\Omega } \cdot $ cm of intrinsic TiO ₂ . Finally, the annealing process eliminates the defects, and therefore, improves electron transport for PSCs, leading to a clearly enhanced fill factor (FF) of 0.77 and conversion efficiency of 19.62% when compared to that of undoped TiO ₂ ETL devices.

Perovskite solar cells (PSCs) based on metal halides have garnered significant attention due to their exceptional power conversion efficiency (PCE) and compatibility with low-temperature fabrication processes. However, the development of stable and inexpensive carbon electrodes remains hindered by issues such as insufficient conductivity at the carbon electrode/perovskite interface and weak coupling strength. In this study, we employed a functionalized carbazole–cellulose composite (C–Cz) as an alternative binder to construct highly stable carbon electrodes for PSCs. The incorporation of C–Cz enhances electron interactions through its conjugated carbazole moieties, while the cellulose backbone facilitates uniform dispersion of carbon particles and forms continuous transport pathways. These synergistic effects significantly optimize interfacial energy alignment and defect passivation. Ultimately, p-i-n PSCs fabricated with C–Cz carbon paste electrodes achieved a champion PCE of 16.79%, substantially outperforming the control device using a conventional PMMA binder (10.56%). Notably, the exceptional hydrophobicity and defect passivation capabilities of the C–Cz electrode substantially enhance device durability—maintaining over 95% of initial efficiency after 400 h of continuous maximum power point tracking irradiation. This study reveals an effective adhesive engineering strategy for robust, scalable carbon electrodes, paving new pathways for practical applications in stable perovskite photovoltaics.