RESUMO
Long-term thermal stability is one limiting factor that impedes the commercialization of the perovskite solar cell. Inspired by our prior results from machine learning, we discover that coating a thin layer of 4,4'-dibromotriphenylamine (DBTPA) on top of a CH3NH3PbI3 layer can improve the stability of resultant solar cells. The passivated devices kept 96% of the original power conversion efficiency for 1000 h at 85 °C in a N2 atmosphere without encapsulation. Near-ambient pressure X-ray photoelectron spectroscopy (XPS) was employed to investigate the evolution of the composition and evaluate thermal and moisture stability by in situ studies. A comparison between pristine MAPbI3 films and DBTPA-treated films shows that the DBTPA treatment suppresses the escape of iodide and methylamine up to 150 °C under 5 mbar humidity. Furthermore, we have used attenuated total reflection Fourier transform infrared and XPS to probe the interactions between DBTPA and MAPbI3 surfaces. The results prove that DBTPA coordinates with the perovskite by Lewis acid-base and cation-π interaction. Compared with the 19.9% efficiency of the pristine sample, the champion efficiency of the passivated sample reaches 20.6%. Our results reveal DBTPA as a new post-treating molecule that leads not only to the improvement of the photovoltaic efficiency but also thermal and moisture stability.
RESUMO
In this Letter, we report for the first time, to the best of our knowledge, a micron-sized mid-infrared Fe2+:ZnSe laser based on a single microcrystal. Typical laser emissions centering at 4.24 µm are observed from a selected Fe2+-doped ZnSe microcrystal under 2.94 µm excitation of Er:YAG laser at room temperature. The laser linewidth is â¼10 nm, the pulse width is â¼50 ns, and the lasing threshold is â¼7.4 mJ/pulse. The lasing wavelength is stable as the pump energy increases and is consistent with the strong absorption position of carbon dioxide in the atmosphere.
