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Author(s): Li-Min Lu [1]; Ling-Feng Mao [2]; Tuo Yang [1]; Jian-Fei Ye [1, 3, 4]; Bing Liu [1, 5]; Hong-Lei Li [6, 7]; Miao Sun [8, 9]; Joseph T. Miller [...]

Metal doping has long been recognized as a general strategy to modify electronic properties of semiconductors. The purpose here is to understand the behavior of oxygen vacancy when existing together with a metal dopant in rutile TiO2 through first‐principles calculation. For the coexistence of an oxygen vacancy and an Ag/Hf dopant, the dopant local effect determines that the formation energy of the oxygen vacancy depends on distances from it to the Ag/Hf dopant. Increased formation energy of an oxygen vacancy adjacent to an Ag dopant is attributed to the fact that the holes produced because of lower valence of Ag than Ti are filled by electrons left by the oxygen vacancy. The same valence of Hf as Ti results in that the electrostatic repulsive force pushes the Hf dopant outward from nearby oxygen vacancy, which lowers the formation energy of the oxygen vacancy. Furthermore, oxygen vacancies coexisting with an Ag/Hf dopant are of interest for investigating the effect of metal doping on the reliability of conductive filaments. The Hf dopant adjacent to the oxygen vacancies greatly enhances the strength of a conductive filament. The built‐in electric fields from localized electrons are considered as the seed action of metal doping in resistive switching devices. [ABSTRACT FROM AUTHOR]

After the contribution of hot carriers to the current in solar cells has been considered, a physical and analytical model of open-circuit voltage is proposed. A variety of experiments on the temperature-dependent open-circuit voltage in solar cells that is one critical factor to determine their overall efficiency are successfully modeled based on the consideration of hot carriers. While previous modeling studies focused on numerical techniques, a physical and analytical model of the open-circuit voltage has been developed. Such a study is an important step toward a quantitative model of solar cells, leading to a deeper understanding of the physical effects in these materials. The analysis of the open-circuit voltage reveals how it depends on temperature, the acceptor density, the light-generated current density, the donor density, the bandgap, the effective mass, and the dielectric constant. A material parameter variation is performed to understand its effects on the open-circuit voltage. It will benefit to optimize the device performance by tuning material parameters through the simplicity and analytic nature of the proposed model. It is also helpful to characterize the material properties using the open-circuit voltage. [ABSTRACT FROM AUTHOR]

The effect of Cu/O/Ti interstitials on the visible-light absorption in Cu2O/TiO2 heterojunctions has been investigated by ab initio methods. The three interstitials are, respectively, doped at the interface of the Cu2O/TiO2 heterojunctions. The Ti interstitial efficiently improves the visible-light absorption, whereas the O interstitial reduces the visible-light absorption. An independent characteristic of the visible-light absorption is found for doping with the Cu interstitial. These phenomena originate from the different concentrations of delocalized electrons induced by the doping atom. The doping with Ti atoms could induce the aggregation of Cu ions, which release more delocalized electrons and so improve the visible-light absorption in a Cu2O/TiO2 heterojunction. [ABSTRACT FROM AUTHOR]