Low-temperature processed tantalum/niobium co-doped TiO2 electron transport layer for high-performance planar perovskite solar cells

A low-temperature preparation process is significantly important for scalable and flexible devices. However, the serious interface defects between the normally used titanium dioxide (TiO2) electron transport layer (ETL) obtained via a low-temperature method and perovskite suppress the further improvement of perovskite solar cells (PSCs). Here, we develop a facile low-temperature chemical bath method to prepare a TiO2 ETL with tantalum (Ta) and niobium (Nb) co-doping. Systematic investigations indicate that Ta/Nb co-doping could increase the conduction band level of TiO2 and could decrease the trap-state density, boosting electron injection efficiency and reducing the charge recombination between the perovskite/ETL interface. A superior power conversion efficiency of 19.44% can be achieved by a planar PSC with a Ta/Nb co-doped TiO2 ETL, which is much higher than that of pristine TiO2 (17.60%). Our achievements in this work provide new insights on low-temperature fabrication of low-cost and highly efficient PSCs.

Automated summary

The development of a low-temperature chemical bath method for co-doping tantalum and niobium in the TiO2 ETL has shown improved conduction band level, reduced trap-state density, enhanced electron injection efficiency, and decreased charge recombination at the perovskite/ETL interface. This results in a superior power conversion efficiency of 19.44% in planar PSCs, providing new insights for low-cost and highly efficient PSCs fabrication.