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In this study, pentabasic CuIn x Ga y Al 1-x-y Se 2 (CIGAS) powder was prepared by heating in ethylene diamine at 290 °C for 20 h, using a solvent thermal reaction technique. The microstructures and electrical properties of the CIGAS targets doped with different aluminum content were investigated by XRD, SEM, XPS and Hall Effect techniques. The results indicate that Al doping had an important effect on the electrical properties and microstructure of the CIGAS targets, especially at the (112) crystal orientation. It was found that the peak of (112) clearly shifted to higher 2θ values with the increase of aluminum incorporation, while the peak intensity weakened gradually, thus indicating that the crystallinity of the CIGAS targets decreased. The SEM results revealed that the sizes of the CIGAS grains could be adjusted by varying the stoichiometric ratio of In, Ga and Al, and that the Al incorporation could enhance the density of the CIGAS targets. The XRD and XPS analysis showed that some In and Ga atoms in the crystal lattice of chalcopyrite structure could be replaced with Al atoms in the CIGAS materials. Finally, the electrical properties of the targets were analyzed based on the Hall Effect measurements. The results showed that the conductivity, mobility and carrier concentration of the targets changed significantly along with the increase of the Al incorporation content, and that the mobility reducing may have been a result of Al incorporation, which prevents the grain from growing, followed by high-density target forming. [ABSTRACT FROM AUTHOR]

The fabrication process for perovskite films is critical for their microstructure and photo-electrical properties. In this study, a pre-preparation step for perovskite crystal particles with a conventional two step spin-coating method was introduced for improving the quality of the prepared perovskite films. By adding CH 3 NH 3 I into the PbI 2 precursor solution and performing anti-solvent extraction during the preparation process, a small amount of perovskite crystal particles was produced in the PbI 2 layers. We demonstrated that the pre-preparation of perovskite crystal particles enhanced the grain size and coverage of the perovskite films due to modification of the surface morphology and crystallisation of the PbI 2 layers. Furthermore, after optimisation, the crystal size in the perovskite films reached almost 3 μm, which tremendously enhanced the generation and transportation of photo-generated carriers in photo-voltaic devices. Under illumination, the fill factor (FF) and short circuit current density (J sc) of the corresponding devices increased, and the photoelectric conversion efficiency (PCE) was enhanced from 11.7% to 17.5%. Further, the stability of the devices in dark humid air was improved. Our results demonstrate that pre-preparing the perovskite crystal particles is useful for the fabrication of high-quality perovskite films. This approach can also be applied to devices based on perovskite films with other compositions. • Sequential deposition method has been improved for the preparation of perovskite films. • The high quality perovskite films were prepared by the pre-crystallisation. • The crystal size in the perovskite films reached almost 3 μm. • The PCE of perovskite solar cells have been greatly improved. [ABSTRACT FROM AUTHOR]