SnO2:TiO2 hybrid nanocrystals as electron transport layer for high-efficiency and stable planar perovskite solar cells

Titanium oxide (TiO2) and tin oxide (SnO2) are the most commonly used electron transport materials for high-efficiency n-i-p perovskite solar cells (PSCs); however, several limiting properties of TiO2 and SnO2 adversely affect device performance. This study describes a facile method to synthesize SnO2:TiO2 hybrid nanocrystals (NCs) to construct electron transport layers (ETLs) with the advantageous properties of both SnO2 and TiO2 for n-i-p PSCs. The optimized SnO2:TiO2 ETL exhibited better surface morphology, well-matched band alignment, higher direct current conductivity, and enhanced electron extraction and transport compared to pristine TiO2 and SnO2 ETLs. Moreover, perovskite films deposited on SnO2:TiO2 ETLs exhibited a higher crystallinity and lower trap-state density than those on TiO2 or SnO2 ETLs. Therefore, SnO2:TiO2-based devices showed high performance (with a power conversion efficiency of 23.19%) and stability (with more than 83% retention of the initial efficiency after 800 h of continuous illumination). This study provides a new method for developing low-cost and efficient ETLs for n-i-p PSCs and confirms that constructing SnO2:TiO2 hybrid ETL is an effective method to fabricate high-efficiency and stable planar perovskite solar cells.