Tunability of the bandgap of SnS by variation of the cell volume by alloying with A.E. elements.

We clarified that the bandgap of inorganic materials is strongly correlated with their effective coordination number (ECoN) via first-principles calculations and experimental confirmations. Tin mono-sulphide (Pnma) and germanium mono-sulphide (Pnma) were selected as model cases since these materials successively alter the ECoN as the cell volume changes and show an uncommon relationship between cell volume and bandgap. Contrary to the common semiconductors, the bandgaps of SnS (Pnma) and GeS (Pnma) have a positive relationship with respect to cell volume.

Impacts of KF Post-Deposition Treatment on the Band Alignment of Epitaxial Cu(In,Ga)Se Heterojunctions.

In this study, we investigated band alignments at CdS/epitaxial CuInGaSe (epi-CIGSe) and epi-CIGSe/GaAs heterointerfaces for solar cell applications using ultraviolet, inverse, and X-ray photoemission spectroscopy (UPS, IPES, and XPS) techniques. We clarified the impacts of KF postdeposition treatment (KF-PDT) at the CdS/epi-CIGSe front heterointerfaces. We found that KF-PDT changed the conduction band alignment at the CdS/epi-CIGSe heterointerface from a cliff to flat configuration, attributed to an increase in the electron affinity () and ionization potential () of the epi-CIGSe surface because of a decrease in Cu and Ga contents.

Improving the Open Circuit Voltage through Surface Oxygen Plasma Treatment and 11.7% Efficient CuZnSnSe Solar Cell.

The photovoltaic performance of CuZnSnSe (CZTSe) solar cells subjected to surface oxygen plasma treatments is investigated. The observed improvements are related to an enhancement of the open circuit voltage V, that is, the suppression of the V deficit. The V monotonically increases with treatment time up to 0.

Band Alignment of the CdS/CuZn(SnGe )Se Heterointerface and Electronic Properties at the CuZn(SnGe )Se Surface: x = 0, 0.2, and 0.4.

The surface electronic properties of the light absorber and band alignment at the p/n heterointerface are key issues for high-performance heterojunction solar cells. We investigated the band alignment of the heterointerface between cadmium sulfide (CdS) and Ge-incorporated CuZnSnSe (CZTGSe), with Ge/(Ge + Sn) ratios ( x) between 0 and 0.4, by X-ray photoelectron, ultraviolet, and inversed photoemission spectroscopies (XPS, UPS, and IPES, respectively).

Highly Controlled Codeposition Rate of Organolead Halide Perovskite by Laser Evaporation Method.

Organolead-halide perovskites can be promising materials for next-generation solar cells because of its high power conversion efficiency. The method of precise fabrication is required because both solution-process and vacuum-process fabrication of the perovskite have problems of controllability and reproducibility. Vacuum deposition process was expected to achieve precise control; however, vaporization of amine compound significantly degrades the controllability of deposition rate.

Formation of ionic bonds between a fatty-acid Langmuir-Blodgett monolayer and a zinc oxide substrate.

A fatty-acid Langmuir-Blodgett (LB) monolayer ionically adsorbed to the substrate has been prepared by adopting ZnO-based conductor and pure water respectively as the substrate and subphase. Ionization of the fatty-acid molecules has been detected by infrared reflection-absorption spectroscopy (IR-RAS), which is enabled by the condensed free electrons in the doped ZnO substrate. On the contrary, IR-RAS measurements have indicated that fatty-acid molecules transferred onto Au and indium-tin-oxide substrates from a pure-water surface are not ionized.

Microstructural evolution of ZnO by wet-etching using acidic solutions.

The characteristics of the wet-etching of ZnO thin films were investigated using hydrochloric and phosphoric acid solutions as etchants. The etch rate of ZnO films, using a highly diluted hydrochloric acid solutions at a concentration of 0.25% in deionized water, was determined to be about 120 nm/min, and linearly increased with increasing the acid concentration.