Titanium-doped SnO2 nanoparticles as the electron transport layer: A pathway to higher open circuit voltage and stability in perovskite solar cells

Tin oxide (SnO₂) is widely used as an electron transport layer (ETL) in planar perovskite solar cells (PSCs) due to its advantageous optical, electrical, and chemical properties. These include high transmittance, minimal UV photocatalytic activity, suitable energy levels, high electron mobility, and excellent chemical stability. Additionally, SnO₂ can be deposited at low temperatures, facilitating the fabrication of flexible PSCs. However, the open circuit voltage (V_OC) in PSCs can decrease due to high defect density and the deeper conduction band (CB) energy level of SnO₂. In this study, titanium (Ti) doping of nanoparticle (NP) SnO₂ ETL is employed to passivate defects and improve charge carrier dynamics in PSCs. The planar PSC utilizing Ti-doped NP-SnO₂ ETL shows a significant increase in V_OC and power conversion efficiency (PCE), achieving values of 1.10 V and 19.75 %, respectively, compared to the undoped variant, which has a V_OC of 1.02 V and a PCE of 17.50 %. Furthermore, the unencapsulated Ti-doped NP-SnO₂ ETL-based PSC retains over 92 % of its initial PCE after approximately 1440 h of storage at room temperature (25–30 °C) with a relative humidity of 20–50 %.