Ozone-Mediated Controllable Hydrolysis for a High-Quality Amorphous NbO Electron Transport Layer in Efficient...

Amorphous NbO electron transport layer (ETL) shows great potential for boosting the power conversion efficiency (PCE) of perovskite solar cells (PSCs) at low temperatures (<100 °C). To date, it is still a challenge to simultaneously control the hydrolysis of the NbO precursor solution and reduce the impurities of NbO ETLs during low-temperature solution processing under ambient conditions. Herein, for the first time, we report ozone (O₃) as a strong ligand to stabilize Nb salt solutions under ambient conditions. The above procedure not only enables the formation of a highly repeatable amorphous NbO film by suppressing the hydrolysis of the solution but also reduces the OH content in the film, which decreases the defect intensity and improves the conductivity of the NbO ETL. Thus, the formation of highly repeatable NbO ETL-based PSCs are obtained; moreover, these PSCs have high PCE values of 19.54 and 16.42% on rigid and flexible substrates, respectively, much higher than the devices based on ETLs from a solution without an O₃ treatment.