Low-temperature solution-processing high quality Nb-doped SnO2 nanocrystals-based electron transport layers for efficient planar perovskite solar cells

Low-temperature solution-processing method is a kind of low-energy-consuming and simple methodology for preparing cost-effective planar perovskite solar cells (PSCs). To achieve high-effciency planar PSCs, the quality of electron-transporting layers (ETLs) play a key role. The solvothermal-synthesized organic ligands capped semiconductor nanocrystals (NCs) not only have high crystallinity but also show excellent film-formation. Nevertheless, the biggest problem is that these organic ligands will form insulating barriers around the NCs, which will seriously hinder electronic coupling and limit performance of the corresponding devices. Therefore, the stripping treatment for organic ligands, which is not only complex but also has destructive influence on the quality of films, is traditionally used for achieving good performance. Here, we select high crystalline oleic acid-capped SnO2 NCs to prepare ETLs with low-temperature solution-processed methodology without complex ligand stripping step. We use Nb[Formula: see text] doping route to further enhance photovoltaic performance of the planar PSCs. The champion PSC based on Nb-doped SnO2 NCs ETL achieves a power conversion efficiency of 20.07%.