SnO₂ Quantum Dot-Modified Mesoporous TiO₂ Electron Transport Layer for Efficient and Stable Perovskite Solar Cells

As a revolutionary photovoltaic technology, the perovskite solar cell has received enormous attention, owing to excellent electronic and optical properties of perovskite materials. The mesoporous TiO2 (m-TiO2) framework is extensively used as an electron transport layer (ETL) to construct high-performance perovskite solar cells (PSCs), showing efficient electron extraction capability, owing to the enlarged perovskite/ETL interface. However, the TiO2 ETL usually involves high-density oxygen vacancies, low electron mobility, and relatively high photocatalytic activity toward perovskite materials. To address such issues, herein, we demonstrate the successful construction of SnO2 quantum dot (QD)-modified m-TiO2 as an effective ETL for PSCs. It is revealed that the SnO2 QD-modified m-TiO2 ETL affords more favorable electron extraction and transport characteristics and suppressed charge recombination, resulting from the interfacial passivation and the enhanced conductivity of ETLs. Furthermore, the ultrathin SnO2 QD layer incorporated at the m-TiO2/perovskite interface effectively lowers the photocatalytic activity of TiO2 toward perovskite materials, thereby improving the long-term device stability. Eventually, the MAPbI3- and FAPbI3-based PSCs utilizing the SnO2 QD-modified m-TiO2 ETLs obtained appreciable power conversion efficiencies of 19.09 and 20.09%, respectively, higher than those of counterpart devices based on the conventional m-TiO2 and SnO2 ETLs.