“…Since the past decade, three-dimensional hybrid organic–inorganic lead halide perovskites (LHPs) have inspired scientists in the field of optoelectronic devices due to their extraordinary optoelectronic properties. , There is particular attention on the application of LHPs as light absorber materials in the next generation of thin film photovoltaic technology, and so-called perovskite solar cells (PSCs) have emerged as a “rising star” due to their high-power conversion efficiency (PCE) exceeding 25%, low cost, and facile fabrication techniques. – To date, highly efficient PSCs are achieved on the regular n–i–p device architecture, in which the surface morphology and chemistry of the electron transport layer (ETL) can affect the deposition and quality of the perovskite layer. , Among various n-type semiconducting materials, SnO 2 stands out as a promising ETL in n–i–p PSCs due to its low-temperature processable synthesis, high optical transmittance, superior electron mobility, and proper band energy alignment with the perovskites . However, the presence of defects (e.g., oxygen vacancy defects) and dangling bonds on the surface of SnO 2 can enhance the nonradiative recombination at the SnO 2 /perovskite interface, affecting device performance and stability. , In this context, many strategies have been undertaken to passivate the surface defects of SnO 2 ETLs to enhance the device’s photovoltaic performance and stability. – This includes doping of the SnO 2 ETL with various metal ions – and interface modification with ionic salts, , organic molecules, , polymers, self-assembled molecules, – or carbon materials …”