High-crystalline-quality CdS thin films with a mono-grained layer of submicron grain size were successfully fabricated. CdS thin films prepared by chemical bath deposition were re-crystallized under different chemical atmospheres. The microstructure of the CdS films, the hetero-junction interface CdS/CdTe, and therefore the solar cell performance were critically dependent on the film process history of the window CdS layers. Heat treatment of a CdS precursor film coated with a CdCl₂ layer and under a high CdCl₂ vapor pressure reduced over-oxidation at the grain surface and promoted in-plane grain coalescence along the CdS/FTO (F-doped SnO₂) interface. A high-crystalline-quality, mono-grain CdS layer ensured homogenous intermixing of CdS and CdTe at the junction interface. A short-circuit current as high as 25.1 mA cm⁻² was obtained for a mono-grain-CdS/CdTe solar cell. The corresponding solar cell efficiency is 14.6%.

Nickel oxide (NiO) has a cubic rock salt crystal structure at room temperature. Raman scattering of the transverse optical (TO) and longitudinal optical (LO) phonon in NiO is Raman inactive. Thus, it is difficult to employ the Raman scattering technique to study the lattice vibration dynamics and spin–phonon coupling in NiO. In this work, crystalline stoichiometry of NiO nanoparticles with different nanocrystalline sizes was tuned to make the Raman scattering selection rules dramatically relaxed. Well-defined Raman scattering peaks of the two zone-boundary folded modes TO(Δ) and LO(Δ) were observed. These two modes are situated at the midpoint along the Γ–Δ–X direction in the Brillouin zone. The Raman scattering of these two modes are induced by magnetostriction and nonstoichiometric Ni–O stretching, respectively. The well-defined Raman peaks of TO(Δ) and LO(Δ) allow us to study the spin–phonon coupling effect in NiO. It is found that spin–phonon coupling is responsible for the Raman scattering anomalies, namely, the relatively large Raman shift hardening and peak width narrowing below the Néel temperature for LO and its overtone 2LO phonons.