Recent advances in the use of organic-inorganic hybrid perovskites for optoelectronics have been rapid, with reported power conversion efficiencies of up to 22 per cent for perovskite solar cells. Improvements in stability have also enabled testing over a timescale of thousands of hours. However, large-scale deployment of such cells will also require the ability to produce large-area, uniformly high-quality perovskite films. A key challenge is to overcome the substantial reduction in power conversion efficiency when a small device is scaled up: a reduction from over 20 per cent to about 10 per cent is found when a common aperture area of about 0.1 square centimetres is increased to more than 25 square centimetres. Here we report a new deposition route for methyl ammonium lead halide perovskite films that does not rely on use of a common solvent or vacuum: rather, it relies on the rapid conversion of amine complex precursors to perovskite films, followed by a pressure application step. The deposited perovskite films were free of pin-holes and highly uniform. Importantly, the new deposition approach can be performed in air at low temperatures, facilitating fabrication of large-area perovskite devices. We reached a certified power conversion efficiency of 12.1 per cent with an aperture area of 36.1 square centimetres for a mesoporous TiO-based perovskite solar module architecture.
Dental caries and periodontal diseases have a close relationship with microbes such as Streptococcus mutans, Porphyromonas gingivalis and Fusobacterium nucleatum. Graphene oxide (GO), as the derivative of graphene, plays an important role in many areas including biology and medicine. In particular, it has been known as a promising antimicrobial nanomaterial. In this study, we focused on the antimicrobial property of GO against dental pathogens. With the utilization of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduced test, colony forming units (CFU) counting, growth curve observation, live/dead fluorescent staining, and confocal laser scanning microscopy (CLSM), we found GO nanosheets were highly effective in inhibiting the growth of dental pathogens. Transmission electron microscopy (TEM) images revealed that the cell wall and membrane of bacteria lost their integrity and the intracellular contents leaked out after they were treated by GO. Therefore, GO nanosheets would be an effective antibacterial material against dental pathogens and the potential applications in dental care and therapy are promising.
Operational stability is crucial for the success in large-scale application of metal halide perovskites devices. The diffusion of volatile iodide component of perovskites can induce irreversible device degradation. Here, low-dimensional diffusion barriers were introduced to increase the operational stability of highefficiency large-area PSC modules. A negligible decay was observed after 1,000 h under severe test condition for a 15% high-efficiency solar module.
Perovskite solar cells are a promising low-cost and highly efficient photovoltaic technology. However, there's still a big challenge in forming large area and uniform perovskite films with a high material utilization ratio. Here we provide a novel continuous processing method, soft-cover deposition, to control the formation of perovskite films in ambient air. High quality films were successfully deposited with less structural defects and high material utilization ratios. Excellent photovoltaic performance was also achieved in a 1 cm 2 unit solar cell, highly reproducible over a large area. The present deposition technology paves the way for future application of high cost-performance perovskite solar cells and the formation of solution processed thin-films.
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