Thin film solar cells based in Cu(In,Ga)Se2 (CIGS) are among the most efficient polycrystalline solar cells, surpassing CdTe and even polycrystalline silicon solar cells. For further developments, the CIGS technology has to start incorporating different solar cell architectures and strategies that allow for very low interface recombination. In this work, ultrathin 350 nm CIGS solar cells with a rear interface passivation strategy are studied and characterized. The rear passivation is achieved using an Al2O3 nanopatterned point structure. Using the cell results, photoluminescence measurements, and detailed optical simulations based on the experimental results, it is shown that by including the nanopatterned point contact structure, the interface defect concentration lowers, which ultimately leads to an increase of solar cell electrical performance mostly by increase of the open circuit voltage. Gains to the short circuit current are distributed between an increased rear optical reflection and also due to electrical effects. The approach of mixing several techniques allows us to make a discussion considering the different passivation gains, which has not been done in detail in previous works. A solar cell with a nanopatterned rear contact and a 350 nm thick CIGS absorber provides an average power conversion efficiency close to 10%.

We report a detailed characterization of an industrylike prepared Cu(In,Ga)S e2 (CIGS)/CdS heterojunction by scanning transmission electron microscopy (S TEM) and photoluminescence (PL). Energy dispersive x-ray spectroscopy (EDS) shows the presence of several regions in the CIGS layer that are Cu deprived and Cd enriched, suggesting the segregation of Cd-S e. Concurrently, the CdS layer shows Cd-deprived regions with the presence of Cu, suggesting a segregation of Cu-S. The two types of segregations are always found together, which, to the best of our knowledge, is observed for the first time. The results indicate that there is a diffusion process that replaces Cu with Cd in the CIGS layer and Cd with Cu in the CdS layer. Using a combinatorial approach we identified that this effect is independent of focused-ion beam sample preparation and of the TEM-grid. Furthermore, photoluminescence measurements before and after an HCl etch indicate a lower degree of defects in the post-etch sample, compatible with the segregates removal. We hypothesize that Cu2-xSe nanodomains react during the chemical bath process to form these segregates since the chemical reaction that dominates this process is thermodynamically favourable. These results provide important additional information about the formation of the CIGS /CdS interface.

Iron silicide samples were grown on Si (111) substrates by solid phase epitaxy and reactive deposition epitaxy. The different iron silicide phases and their correlations with the growth parameters were analyzed by x-ray photoelectron spectroscopy, conversion electron Mössbauer spectroscopy, x-ray diffraction, atomic force microscopy, and magnetic force microscopy. The authors investigated the potential of each technique for identifying and quantifying of the phases. In particular, the authors used a semiquantitative analysis of magnetic force microscopy images to spatially resolve the semiconductor β-FeSi2 phase.

The original goal of our study is to synthesize by co-evaporation the phase that could be formed at the interface between polycrystalline p-Cu(In,Ga)Se 2 treated with KF and n-CdS. Hence, a new buffer layer, CdIn 2 S 4 (C24), deposited by co-evaporation is presented for the use in thin film solar cells, exhibiting device efficiencies as high as 16.2%, comparable to that obtained on a reference standard CdS-buffered device. The physico-chemical and optical properties of close to stoichiometry 400 nm-thick films of C24 show similar properties to what has been reported in the literature for single crystals. The layer stack used for solar cells is investigated by transmission electron microscopy, showing the formation of an ultrathin Cd-deficient C24 layer at the CIGSe/C24 interface, while a clear lattice match is observed at the C24/ZnO interface. Advanced electrical characterizations of the devices suggest that the output voltage and fill factor of the solar cells based on Cu(In,Ga)Se 2 /(PVD)C24 are limited by tunneling-enhanced recombination through extended band tail states. These results open new routes to explain the superiority of wet processes used for the junction formation compared to vacuum-based approaches.

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The electronic structure of highly Si-doped GaAs NWs is ruled by fluctuating potentials: luminescence intensity increase and polytypism influence reduction.

The role of two defects in the ambipolar character of nanocrystalline selenium poor Sb2Se3 is studied. At low temperature, the electrical transport in Sb2Se3 thin films with nm‐sized crystallites and grains is dominated by the ionization of a shallow acceptor, while at high temperature a deep donor is the leading one. The ionization energy of the deep donor agrees with theoretical reports for selenium vacancies. However, the value of the ionization energy of the shallow acceptor is in contradiction with theoretical reports pointing out to an unreported shallow defect. These findings have been confirmed by two independent experimental techniques, Electron Paramagnetic Resonance, and electrical transport as a function of temperature. The mobility of the free carriers has been found not to be limited by grain potential barriers (GPB), in contrast with polycrystalline thin films. Both findings, new shallow acceptor and zero height GPB, constitute advantages for the design of nanostructured Sb2Se3‐based solar cells and other optoelectronic devices. These results not only provide useful information for the growth of nanocrystalline Sb2Se3 thin films with ambipolar transport properties, but also about the complexity of defect physics in low‐symmetry and Q1D semiconductors.

On the left a schematic of an ultrathin Cu(In,Ga)Se2 solar cell with passivated rear interface and on the right a transmission electron microscopy of the real device. In article number https://doi.org/10.1002/admi.201701101 Pedro M. P. Salomé and co‐workers show a significant reduction in the rear recombination, improving the electrical performance of solar cells.