Speaker
Description
The requirements of electron transport layer (ETL) for high efficiency Perovskite solar cells (PSCs) are, for example, appropriate band energy alignment, high electron mobility, high optical transmittance, high stability, and easy processing. The metal-oxide ETLs that have been proposed for PSCs are, such as, TiO2, SnO2, etc. TiO2 is usually used for ETL as a compact layer and a mesoporous layer. Both layers give relatively higher efficiency PSCs. However, TiO2 layer has some limitations for PSCs such as it needs high-temperature process and yields low electron mobility. The effect of TiO2 layer negatively affects the device stability under ultraviolet (UV) illumination. Recently, SnO2 has attracted more attention as ETL for PSCs because it has diverse advantages, e.g., wide bandgap energy (3.5 – 4.0 eV), excellent optical and chemical stability, high transparency, high electron mobility (~240 cm2/V.s), and easy preparation. The SnO2 ETL was fabricated by RF magnetron sputtering technique to ensure the chemical composition and uniform layer thickness when compared to the use of chemical solution via spin-coating method. The RF power was varied from 60 – 150 W. The Ar sputtering gas pressure was varied from 1x10-3 – 6x10-3 mbar while keeping O2 partial pressure at 1x10-4 mbar. The thickness of SnO2 layer decreases as the Ar gas pressure increases resulting in the increase of sheet resistance. The surface morphology and optical transmission of the SnO2 ETL were investigated. It was found that the optimum thickness of SnO2 layer was approximately 35 – 40 nm. The best device shows Jsc = 27.4 mA/cm2, Voc = 1.03 V, fill factor = 0.63, and efficiency = 17.7%.