2, Huazhong University of Science and Technology, Wuhan, , China
The highly diverse and adaptable architectures of the PSCs is also one of the key steps that leading PSCs to the forefront of the emerging PV technologies. Among various device configurations, the “n-i-p” planar structure without secondary mesoporous layers has attracted lots of attention due to its simple device fabrication process; where n-type metal oxides have been widely applied as the first layer on top of the FTO or ITO. TiO2 is the most commonly used electron transport material in the PSCs due to its mature development in the field of DSSCs, however, several studies have pointed out that TiO2 may not be the best candidate to carry PSCs toward commercialization due to its unfavorable properties, including UV instability, high-temperature sintering process, large energy level offset, etc. On the contrary, SnO2 emerged as an ideal n-type layer for PSCs recently, with advantages of higher electron mobility, low-temperature process, and UV-stabled properties. However, SnO2 behaves quite differently while prepared by different methods.
In this work we devised a facile strategy to combine the strength of two different SnO2. Interestingly, we found the bilayer displays better energy level alignment with perovskite, faster charge extraction, and lower trap-density. As a result, the photovoltaic devices based on this electron transport layers demonstrate a superior power conversion efficiency up to 20.5% with VOC close to 1.2 V and negligible J-V hysteresis in the device.