This review initially describes the recent progress in SnO ₂ nanostructures, preparation methods and passivation options. Then, the challenges and limitations of SnO ₂ ETL-based PSCs were discussed and recommendations for further research were made.

A rapid and simple process to prepare CH₃NH₃PbI₃ perovskite solar cells in ambient air by adding 2-pyridylthiourea in the precursor solution was reported. The newly developed PSC exhibited an enhanced PCE of 18.2% along with enhanced stability under heat and humidity.

The stability of perovskite solar cells is still one issue that needs to be solved, though remarkable success has been achieved since its first report in 2009. In this work, two thiadiazole derivatives (1,3,4-thiadiazolidine-2-thione, TDZT and 1,3,4-thiadiazolidine-2,5-dithione, TDZDT) were added into a perovskite precursor to modulate CH₃NH₃PbI₃ perovskite crystal growth. Thiadiazole derivatives can allow the size of the CH₃NH₃PbI₃ crystals to exceed 800 nm and can reduce the grain boundaries. The defect density, calculated using the space charge limited current (SCLC) method for perovskite, was 7 times lower when a certain amount of TDZDT was added. As a result, we obtained a power conversion efficiency (PCE) of 19.04% accompanied by excellent stability under humidity and heat. The unsealed devices retained 91.2% of their initial PCE after 1200 h in 65 ± 5% relative humidity at room temperature under dark conditions, and over 90% of their initial PCE after 840 h of aging in 30% relative humidity and ambient air at 60–75 °C under dark conditions. The result showed that these thiadiazole derivatives can effectively suppress the defects, thus improving the efficiency and stability of the perovskite solar cells.

Passivation and hydrophobic effects can significantly enhance the stability and optoelectronic properties of MAPbI₃ films.