Key Sputtering Parameters for Precursor InO Films to Achieve High Carrier Mobility.

Owing to their extremely high carrier mobility (μ) of >100 cm/(V s) and suitable low carrier concentrations, transparent conducting films of solid-phase crystallized H-doped InO (spc-IO:H) exhibit high conductivity with high optical transparency over a broad frequency range. These properties can be attributed to solid-phase crystallization of the amorphous precursor film. Therefore, the development of high-quality spc-IO:H films requires the deposition conditions of the precursor films to be optimized.

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.

New Route for "Cold-Passivation" of Defects in Tin-Based Oxides.

Transparent conductive oxides (TCOs) are essential in technologies coupling light and electricity. For Sn-based TCOs, oxygen deficiencies and undercoordinated Sn atoms result in an extended density of states below the conduction band edge. Although shallow states provide free carriers necessary for electrical conductivity, deeper states inside the band gap are detrimental to transparency.

Si-Doping Effects in Cu(In,Ga)Se Thin Films and Applications for Simplified Structure High-Efficiency Solar Cells.

We found that elemental Si-doped Cu(In,Ga)Se (CIGS) polycrystalline thin films exhibit a distinctive morphology due to the formation of grain boundary layers several tens of nanometers thick. The use of Si-doped CIGS films as the photoabsorber layer in simplified structure buffer-free solar cell devices is found to be effective in enhancing energy conversion efficiency. The grain boundary layers formed in Si-doped CIGS films are expected to play an important role in passivating CIGS grain interfaces and improving carrier transport.

Cu(In,Ga)Se Solar Cells with Amorphous InO-Based Front Contact Layers.

Amorphous (a-) InO-based front contact layers composed of transparent conducting oxide (TCO) and transparent oxide semiconductor (TOS) layers were proved to be effective in enhancing the short-circuit current density (J) of Cu(In,Ga)Se (CIGS) solar cells with a glass/Mo/CIGS/CdS/TOS/TCO structure, while maintaining high fill factor (FF) and open-circuit voltage (V). An n-type a-In-Ga-Zn-O layer was introduced between the CdS and TCO layers. Unlike unintentionally doped ZnO broadly used as TOS layers in CIGS solar cells, the grain-boundary(GB)-free amorphous structure of the a-In-Ga-Zn-O layers allowed high electron mobility with superior control over the carrier density (N).

Carrier Compensation Induced by Thermal Annealing in Al-Doped ZnO Films.

This study investigated carrier compensation induced by thermal annealing in sputtered ZnO:Al (Al₂O₃: 0.25, 0.5, 1.