Electron-beam-induced current at absorber back surfaces of Cu (In,Ga) Se2 thin-film solar cells

The following article appeared in Journal of Applied Physics 115.1 (2014): 014504 and may be found at http://scitation.aip.org/content/aip/journal/jap/115/1/10.1063/1.4858393The present work reports on investigations of the influence of the microstructure on electronic properties of Cu(In,Ga)Se2 (CIGSe) thin-film solar cells. For this purpose, ZnO/CdS/CIGSe stacks of these solar cells were lifted off the Mo-coated glass substrates. The exposed CIGSe backsides of these stacks were investigated by means of electron-beam-induced current (EBIC) and cathodoluminescence (CL) measurements as well as by electron backscattered diffraction (EBSD). EBIC and CL profiles across grain boundaries (GBs), which were identified by EBSD, do not show any significant changes at Σ3 GBs. Across non-Σ3 GBs, on the other hand, the CL signals exhibit local minima with varying peak values, while by means of EBIC, decreased and also increased short-circuit current values are measured. Overall, EBIC and CL signals change across non-Σ3 GBs always differently. This complex situation was found in various CIGSe thin films with different [Ga]/([In]+[Ga]) and [Cu]/([In]+[Ga]) ratios. A part of the EBIC profiles exhibiting reduced signals across non-Σ3 GBs can be approximated by a simple model based on diffusion of generated charge carriers to the GBs.This work was supported in part by the BMU projects comCIGS and comCIGSII. R.C. acknowledges financial support from Spanish MINECO within the program Ramon y Cajal (RYC-2011-08521)

Differential neuronal vulnerability identifies IGF-2 as a protective factor in ALS

The fatal disease amyotrophic lateral sclerosis (ALS) is characterized by the loss of somatic motor neurons leading to muscle wasting and paralysis. However, motor neurons in the oculomotor nucleus, controlling eye movement, are for unknown reasons spared. We found that insulin-like growth factor 2 (IGF-2) was maintained in oculomotor neurons in ALS and thus could play a role in oculomotor resistance in this disease. We also showed that IGF-1 receptor (IGF-1R), which mediates survival pathways upon IGF binding, was highly expressed in oculomotor neurons and on extraocular muscle endplate. The addition of IGF-2 induced Akt phosphorylation, glycogen synthase kinase-3\u3b2 phosphorylation and \u3b2-catenin levels while protecting ALS patient motor neurons. IGF-2 also rescued motor neurons derived from spinal muscular atrophy (SMA) patients from degeneration. Finally, AAV9::IGF-2 delivery to muscles of SOD1G93A ALS mice extended life-span by 10%, while preserving motor neurons and inducing motor axon regeneration. Thus, our studies demonstrate that oculomotor-specific expression can be utilized to identify candidates that protect vulnerable motor neurons from degeneration

Microscopic origins of performance losses in highly efficient Cu In, Ga Se2 thin film solar cells

Thin film solar cells based on polycrystalline absorbers have reached very high conversion efficiencies of up to 23 25 . In order to elucidate the limiting factors that need to be overcome for even higher efficiency levels, it is essential to investigate microscopic origins of loss mechanisms in these devices. In the present work, a high efficiency 21 without anti reflection coating copper indium gallium diselenide CIGSe solar cell is characterized by means of a correlative microscopy approach and corroborated by means of photoluminescence spectroscopy. The values obtained by the experimental characterization are used as input parameters for two dimensional device simulations, for which a real microstructure was used. It can be shown that electrostatic potential and lifetime fluctuations exhibit no substantial impact on the device performance. In contrast, nonradiative recombination at random grain boundaries can be identified as a significant loss mechanism for CIGSe solar cells, even for devices at a very high performance leve

Laser capture microscopy coupled with Smart-seq2 for precise spatial transcriptomic profiling.

Laser capture microscopy (LCM) coupled with global transcriptome profiling could enable precise analyses of cell populations without the need for tissue dissociation, but has so far required relatively large numbers of cells. Here we report a robust and highly efficient strategy for LCM coupled with full-length mRNA-sequencing (LCM-seq) developed for single-cell transcriptomics. Fixed cells are subjected to direct lysis without RNA extraction, which both simplifies the experimental procedures as well as lowers technical noise. We apply LCM-seq on neurons isolated from mouse tissues, human post-mortem tissues, and illustrate its utility down to single captured cells. Importantly, we demonstrate that LCM-seq can provide biological insight on highly similar neuronal populations, including motor neurons isolated from different levels of the mouse spinal cord, as well as human midbrain dopamine neurons of the substantia nigra compacta and the ventral tegmental area

Preferred orientation, grain sizes and grain boundaries of chalcopyrite type thin films

Chalcopyrite type thin films CuInS2, CuInSe2, CuGaSe2, and Cu In,Ga Se2 in various completed solar cells were studied in cross section by means of electron backscatter diffraction EBSD . Valuable information on grain sizes, local grain orientations, film textures, and grain boundaries were extracted from the EBSD linescans and maps. The grain size distributions from the chalcopyrite type thin films can be represented well by lognormal distribution functions. The EBSD measurements on CuGaSe2 thin film reveal a lt;110 gt; fiber texture, in good agreement with x ray diffraction texture analysis performed on the same sample. The EBSD maps from all samples studied exhibit considerable twinning in the chalcopyrite type thin films. Indeed, the most frequent types of grain boundaries in these thin films are near amp; 931;3 60 lt;221 gt; and 71 lt;110 gt; twins. It is shown that rotational 180 lt;221 gt; twins which are symmetrically equivalent to 71 lt;110 gt; are more frequently found than anion or cation terminated 60 lt;221 gt; twin boundarie

Compositional dependence of charge carrier transport in kesterite Cu2ZnSnS4 solar cells

Cu2ZnSnS4 solar cells deposited by thermal co evaporation have been characterized structurally and electronically to determine the dependence of the electronic properties on the elemental composition of the kesterite phase, which can significantly deviate from the total sample composition. To this end, the kesterite phase content and composition were determined by a combination of X ray fluorescence and X ray absorption measurements. The electronic properties, such as carrier density and minority carrier diffusion length, were determined by electron beam induced current measurements and capacitance voltage profiling. The charge carrier transport properties are found to strongly depend on the Cu Sn Zn ratio of the kesterite phase. For the Cu poor sample, a minority carrier diffusion length of 270 amp; 8201;nm and a total collection length of approx. 500 amp; 8201;nm are deduced, indicating that current collection should not be an issue in thin device