Search

GaN crystals are synthesized by recrystallization technique in Na-Li-Ca alloy melt under different N2 pressure. X-ray powder diffraction results confirm that the structure of crystals is GaN with wurtzite type and there still have raw powders remaining. The total mass of GaN decreases with the nitrogen pressure reduces. No GaN crystals are found in the solution under N2 pressure of 0.4 MPa. The morphologies of the crystal are mainly prism and pyramid. The size of the crystal increases when closer to the liquid surface. Raman spectra indicates that these crystals are stress-free and crystal grown at 3.6 MPa has high structural quality or low impurity concentrations. The results reveal that the solubility and supersaturation of the solution are controlled by N2 pressure. The principle of GaN crystal synthesis by recrystallization is discussed. [ABSTRACT FROM AUTHOR]

So far, it is still a great challenge to prepare high efficiency organic–inorganic perovskite solar cells in ambient air. Specifically, moisture is easily combined with the perovskite material during the spin-coating process, which result in porous perovskite films with poor surface morphology. In this study, we investigated crystalline Ag-doped perovskite films by a one-step spin-coating method in air with 30–40% relative humidity (RH), in which ethyl acetate (EA) was used as antisolvent can absorb moisture in air to reduced nucleation density. More significantly, EA is a feasible and environmentally friendly solvent to replace highly toxic solvent. Moreover, 1.0% Ag-doped device shows a highest power conversion efficiency (PCE) of 14.36%. The improved performance is not only ascribed to the superior CH3NH3PbI3 film with high crystallinity but to the versatile tunability of energy band structure. [ABSTRACT FROM AUTHOR]