The material and microstructure of the carrier-selective layers in the perovskite solar cells are important to determining their efficiency and stability. Planar SnO 2 is the most commonly used inorganic electron transport layer, but there are few reports of its mesoporous structure because of the degradation of hole-blocking property after high temperature sintering. Here, the chemical bath deposition method was optimized to realize low-temperature in-situ deposition of mesoporous SnO 2 layer on FTO substrates. On one hand, the increased interface contact area improves electron injection from the perovskite layer to the SnO 2 , yielding an impressive increase of the power conversion efficiency from 22.09% to 24.11%. And on the other hand, thanks to the increased mechanical strength of the interface, the device with mesoporous SnO 2 retains 90% of its initial power conversion efficiency after 1000 h operation under continuous one-sun illumination.
Electron transport layer (ETL) is very critical to the performance of perovskite solar cells (PSCs), and optimization work on ETL has received extensive attentions especially on tin oxide (SnO 2 ) since it is an excellent ETL material widely applied in high-efficiency PSCs. Thereinto, introducing mesoporous structure and surface modification are two important approaches which are commonly applied. Herein, based on the previous work in low-temperature fabrication process of mesoporous SnO 2 (m-SnO 2 ), we introduced a modification process with rubidium fluoride (RbF) to the m-SnO 2 ETL, and successfully achieved a synergy of the m-SnO 2 and RbF modification: not only the shortcoming of the m-SnO 2 in interfacial traps was overcome, but also the carrier collection efficiency was further improved. The PSCs based on the m-SnO 2 ETL with RbF modification demonstrated outstanding performances: a champion power conversion efficiency (PCE) of 22.72% and a stability performance of maintaining 90% of the initial PCE after 300 h of MPP tracking were obtained without surface passivation of perovskite film. Hence, utilizing the abovementioned synergy is a cost-effective and feasible strategy for fabricating high-efficiency and stable PSCs since the fabrication process of the m-SnO 2 ETL is a kind of low temperature process and RbF is cheap.
A unique hierarchical mesoporous SnO2 microflower was utilized for the fabrication of an immunosensor. The modified nitrogen-doped carbon quantum dots (NCQDs) improved the photoelectrochemical (PEC) activity of the SnO2, and contributed to the in situ assembly of Bi2S3 nanoparticles on the surface of the SnO2 materials. Under the stimulation of visible light and ascorbic acid as an efficient electron donor, the NCQDs and Bi2S3 co-sensitized mesoporous SnO2 microflower (SnO2/NCQDs/Bi2S3) modified ITO electrode exhibited an excellent photoelectric signal arriving at around 150 μA. Moreover, a novel label-free PEC sensor based SnO2/NCQDs/Bi2S3 composite was constructed, which enabled the ultrasensitive detection of N-terminal pro-B-type natriuretic peptide (NT-proBNP). The photocurrents decreased linearly with the logarithm of NT-proBNP concentration in the range of 0.01–50 ng mL−1 with a detection limit of 3.7 pg mL−1 (S/N = 3). Furthermore, the novel PEC immunosensor showed perfect selectivity, good stability and reproducibility, which suggest promising applications in the sensing and clinical diagnosis of cardiac disease.
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