The effects of RbF postdeposition treatment (RbF-PDT) on Cu­(In,Ga)­Se2, CuInSe2, and CuGaSe2 thin films and solar cell devices are comparatively studied. Similar to the effect of the KF postdeposition treatment (KF-PDT), Cu­(In,Ga)­Se2 and CuInSe2 film surfaces show significant pore formation resulting in a rough surface morphology with RbF-PDT, whereas this is not the case for In-free CuGaSe2. The device properties of the In-containing and In-free Cu­(In,Ga)­Se2 solar cells also show contrasting results, namely, Cu­(In,Ga)­Se2 or CuInSe2 devices show an increase in the open circuit voltage (V oc) and fill factor (FF) values and almost constant or a slight decrease in the short-circuit current density (J sc) values with RbF-PDT, whereas CuGaSe2 devices show no significant improvements in the V oc and FF values but a substantial increase in the J sc values. These results suggest that the alkali effects on the Cu­(In,Ga)­Se2 film and device properties strongly depend on the group III elemental composition in the Cu­(In,Ga)­Se2 films as well as alkali-metal species.

Scanning transmission electron microscopy-energy dispersive X-ray spectroscopy measurements performed on Cu(In,Ga)Se2 (CIGS) thin-film devices grown with RbF postdeposition treatment (RbF-PDT) revealed the formation of a RbInSe2 compound at the p-CIGS/n-CdS heterointerface. However, this type of Rb-compound formation was not observed with elemental In-free ternary CuGaSe2 (CGS) devices. The film surface of CIGS grown with RbF-PDT was found to be Ga-depleted; thus, the practical interface structure turned out to be CIGS/(CuInSe2, RbInSe2)/CdS. In contrast to the significant improvements observed in In-containing CIGS photovoltaic device performance with RbF-PDT, no significant improvements have been observed in In-free CGS devices thus far. These results suggest that the presence of elemental In plays a key role in obtaining beneficial alkali Rb effects for enhancing device performance as well as surface modification with RbF-PDT.

No abstract

No abstract

We report a scandium oxyhydride BaScOH prepared by solid state reaction under high pressure. Rietveld refinements against powder synchrotron X-ray and neutron diffraction data revealed that BaScOH adopts the ideal cubic perovskite structure (Pm3̅m), where oxide (O) and hydride (H) anions are disordered. H nuclear magnetic resonance (NMR) spectroscopy provides a positive chemical shift of about +4.4 ppm, which can be understood by the distance to the nearest (and possibly the next nearest) cation from the H nucleus. A further analysis of the NMR data and calculations based on ab initio random structure searches suggest a partial cis preference in ScOH octahedra. The present oxyhydride, if compositionally or structurally tuned, may become a candidate for H conductors.