In this contribution, we present a new certified world record efficiency of 20.1 and 20.3% for Cu(In,Ga)Se2 thin-film solar cells. We analyse the characteristics of solar cells on such a performance level and demonstrate a high degree of reproducibility. Copyright © 2011 John Wiley & Sons, Ltd.

New world record efficiency for Cu(In,Ga)Se2 thin‐film solar cells beyond 20%

Since the discovery of superconductivity above 30 K by Bednorz and M\"uller in the La copper oxide system, the critical temperature has been raised to 90 K in Y${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ and to 110 and 125 K in Bi-based and Tl-based copper oxides, respectively. In the two years since this Nobel-prize-winning discovery, a large number of electronic structure calculations have been carried out as a first step in understanding the electronic properties of these materials. In this paper these calculations (mostly of the density-functional type) are gathered and reviewed, and their results are compared with the relevant experimental data. The picture that emerges is one in which the important electronic states are dominated by the copper $d$ and oxygen $p$ orbitals, with strong hybridization between them. Photon, electron, and positron spectroscopies provide important information about the electronic states, and comparison with electronic structure calculations indicates that, while many features can be interpreted in terms of existing calculations, self-energy corrections ("correlations") are important for a more detailed understanding. The antiferromagnetism that occurs in some regions of the phase diagram poses a particularly challenging problem for any detailed theory. The study of structural stability, lattice dynamics, and electron-phonon coupling in the copper oxides is also discussed. Finally, a brief review is given of the attempts so far to identify interaction constants appropriate for a model Hamiltonian treatment of many-body interactions in these materials.

Electronic structure of the high-temperature oxide superconductors

Premises of creation of Internet portal designed to provide access to participants of educational and scientific process for the joint creation, consolidation, concentration and rapid spreading of educational and scientific information resources in its own depository are considered. CMS-based portal content management systems’ potentiality is investigated. Architecture for Internet portal of MES of Ukraine’s information resources is offered.

Створення порталу інформаційно-довідкових ресурсів міністерства освіти і науки україни

Solar photovoltaic electricity: Current status and future prospects

The discovery of 30-K superconductivity in the La–Ba–Cu–O system1 and 90-K superconductivity in the Y–Ba–Cu–O system2 stimulated a worldwide search for even higher-temperature superconductors. Unfortunately, most of the higher-temperature transitions reported in the past year have proved to be unstable, irreproducible, or not due to bulk superconductivity3–7. Recently, we and co-workers8,9 reported superconductivity above 90 K in a new Tl–Ba–Cu–O system, and pointed out that elemental substitutions in this system may lead to even higher-temperature superconductivity. Here we report stable and reproducible bulk superconductivity with an onset at 120 K and zero resistance above 100 K in the Tl–Ca/Ba–Cu–O system. This transition temperature is much higher than those observed for typical rare-earth-containing superconductors, and the onset temperatures are comparable to that in the Bi–Ca/Sr–Cu–O system, as reported in refs 10 and 11 (received after submission of this paper).

Bulk superconductivity at 120 K in the Tl-Ca/Ba-Cu-O system

The anisotropic resistivity and paraconductivity of Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} single crystals were measured. The in-plane and {ital c}-axis resistivities are, respectively, {similar to}7{times}10{sup {minus}4} and 10{sup {minus}1} {Omega} cm at room temperature. The {ital c}-axis resistivity decreases with decreasing temperature in the temperature range from room temperature down to the superconducting transition temperature, and the second derivative of {rho}{sub {ital c}} is negative, which is not characteristic of YBa{sub 2}Cu{sub 3}O{sub 7} and Bi{sub 2}Sr{sub 2.2}Ca{sub 0.8}Cu{sub 2}O{sub 8} single crystals, in which the second derivative is either positive or zero. The in-plane paraconductivity is obtained from the in-plane resistivity, and a method without the critical temperature as an adjustable parameter is employed to obtain the dimensionality. The data show that the superconductivity is two dimensional, but a crossover from two to three dimensions has also been observed near the transition temperature in some samples.

Anisotropic resistivity and paraconductivity of Tl2Ba2CaCu2O8 single crystals.

Spectroscopic ellipsometry measurements of CuInSe2 (CIS) and CuIn0.8Ga0.2Se2 (CIGS) reveal that there are important differences in electronic properties between stoichiometric CIS (CIGS) and Cu-poor CIS (CIGS). We find a reduction in the absorption strength in the spectral region of 1–3eV. This reduction can be explained in terms of the Cu 3d density of states. Cu-poor CIS (CIGS) materials show an increase in band gap due to the reduction in repulsion between Cu 3d and Se 4p states. The experimental results have important implications for the function of polycrystalline optoelectronic devices.

Effect of Cu deficiency on the optical properties and electronic structure of CuInSe2 and CuIn0.8Ga0.2Se2 determined by spectroscopic ellipsometry

A new process for making Tl‐Ba‐Ca‐Cu‐O superconductors which is based on reactions between solid precursor Ba‐Ca‐Cu‐oxides and vapor Tl2O3 has been developed. The Tl2O3 vapor process allows Tl‐Ba‐Ca‐Cu‐O superconductors to be easily made in the forms of complex bulk components, wires and fibers, and thick and thin films, and minimizes problems caused by toxicity and volatility of Tl starting compounds.

Tl2O3 vapor process of making Tl‐Ba‐Ca‐Cu‐O superconductors

We report measurements of the thermoelectric power of the high-temperature Tl-Ca-Ba-Cu-O superconductor. The data indicate a transition which is centered at 118 +- 3 K, in agreement with magnetic measurements and published resistivity results. The thermoelectric power is positive and, aside from the high transition temperature, is remarkably similar in magnitude and temperature dependence to that of the rare-earth-based oxide superconductors which have been reported previously.

Thermoelectric power of the Tl-Ca-Ba-Cu-O superconductor.

The near-surface region of thin-film polycrystalline (PX) CuIn1−xGaxSe2 (CIGS) is considered important because it is the region where the electrical junction forms in a CIGS photovoltaic device. Spectroscopic ellipsometry measurements of polycrystalline CuInSe2 films reveal that there is a thin layer at the surface which has different optical and electronic properties from those of the bulk film. This surface layer of thin-film CIGS has a larger band gap and greater spin-orbit interaction energy than the bulk film. These properties indicate that the surface layer is more Cu deficient than the bulk in the nearly stoichiometric thin-film PX-CIGS used in photovoltaic devices. This work provides an insight into the importance of surface layer engineering for photovoltaic device design.

/pdf/spectroscopic-evidence-for-a-surface-layer-in-cuinse2-cu-54o4tfs6rc.pdf

Allen M. Hermann

Papers

Anisotropic resistivity and paraconductivity of Tl2Ba2CaCu2O8 single crystals.

Effect of Cu deficiency on the optical properties and electronic structure of CuInSe2 and CuIn0.8Ga0.2Se2 determined by spectroscopic ellipsometry

Tl2O3 vapor process of making Tl‐Ba‐Ca‐Cu‐O superconductors

Thermoelectric power of the Tl-Ca-Ba-Cu-O superconductor.

Spectroscopic evidence for a surface layer in CuInSe2:Cu deficiency