Infection causes childhood leukemia

This is an open-access article distributed under the terms of the Creative Commons Attribution License.-- Editorial.Peer Reviewe

High-efficiency solar cells based on inversion layer emitters

In crystalline silicon (c-Si) solar cells based on p-type substrates, inversion layer emitters have been proposed as an alternative to high-temperature phosphorus diffusion. Dielectric film deposition at low temperature (≤400 ºC) is widely used for c-Si surface passivation and in this case emitters are induced by the positive fixed charge,Qf, at the c-Si/dielectric interface. In this work, we use 2-D simulations to explore solar cell structures with inversion layer emitters placed between local n+-emitters. The local diffusions could be defined by laser processing, resulting in potentially low-temperature processed structures. From simulation results, the low conductivity of inversion layer emitters obligates to short contact spacing and, hence, dense front grids and high shadow losses. However, placing the emitter at the back reduces these penalties, increasing the efficiency about 1% absolute. Furthermore, taking advantage of the fully metallized back surface, inversion layer emitters can be assisted by the workfunction difference between the c-Si substrate and the metal (typically aluminum) over the dielectric. As a result, the necessity of a high positive Qf value is relaxed.Postprint (published version

TCO-free low-temperature p+ emitters for back-junction c-Si solar cells

In this work, we report on the fabrication and characterization of n-type c-Si solar cells whose p+ emitters are based on laser processed aluminum oxide/silicon carbide (Al2O3/SiCx) films. The p+ emitter is defined at the rear side of the cell and it consists of point-like laser-diffused p+ regions with a surface charge induced emitter in between based on the high negative charge located at the Al2O3/c-Si interface. These emitters are fabricated at low temperature (1000 nm) that reach the rear surface of the cell resulting in an excellent back reflector. We fabricated solar cells with distance between p+ regions or pitch ranging from 200 to 350 µm with a front surface based on silicon heterojunction technology. Best efficiency (18.1%) is obtained for a pitch of 250 µm as a consequence of the trade-off between Voc and FF values.Peer ReviewedPostprint (published version

Numerical simulations of rear point-contacted solar cells pn 2.2 Wcm p-type c-Si substrates

Rear surface of high-efficiency crystalline silicon solar cells is based on a combination of dielectric passivation and point-like contacts. In this work, we develop a 3D model for these devices based on 2.2 Ωcm p-type crystalline silicon substrates. We validate the model by comparison with experimental results allowing us to determine an optimum design for the rear pattern. Additionally, the 3D model results are compared with the ones deduced from a simpler and widely used 1D model. Although the maximum efficiency predicted by both models is approximately the same, large deviations are observed in open-circuit voltage and fill factor. 1D simulations overestimate open-circuit voltage because Dember and electrochemical potential drops are not taken into account. On the contrary, fill factor is underestimated because of higher ohmic losses along the base when 1D analytical model is used. These deviations are larger for relatively low-doped substrates, as the ones used in the experimental samples reported hereby, and poor passivated contacts. As a result, 1D models could mislead to too short optimum rear contact spacing.Peer ReviewedPostprint (published version

Early epigenetic cancer decisions

A cancer dogma states that inactivation of oncogene(s) can cause cancer remission, implying that oncogenes are the Achilles' heel of cancers. This current model of cancer has kept oncogenes firmly in focus as therapeutic targets and is in agreement with the fact that in human cancers all cancerous cells, with independence of the cellular heterogeneity existing within the tumour, carry the same oncogenic genetic lesions. However, recent studies of the interactions between an oncogene and its target cell have shown that oncogenes contribute to cancer development via developmental reprogramming of the epigenome within the target cell. These results provide the first evidence that carcinogenesis can be initiated by epigenetic stem cell reprogramming, and uncover a new role for oncogenes in the origin of cancer. Here we analyse these evidences and discuss how this vision offers new avenues for developing novel anti-cancer interventions.Research in our group is partially supported by FEDER and by MICINN (SAF2012-32810), by NIH grant (R01 CA109335-04A1), by the ARIMMORA project (FP7-ENV-2011, European Union Seventh Framework Program), by Junta de Castilla y Leon (BIO/SA06/13), and by the Deutsche José Carreras Leukämie-Stiftung (DJCLS project 13/26). All Spanish funding is co-sponsored by the European Union FEDER program. ISG is an API lab of the EuroSyStem project and a partner within the Marie Curie Initial Training Network DECIDE (Decision-making within cells and differentiation entity therapies) funded by the European Union’s Seventh Programme under grant agreement n° 315902.Peer Reviewe

Textured PDMS films applied to thin crystalline silicon solar cells

© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Front surface texturization is a standard procedure used to improve optical properties of photovoltaic devices. In some particular cases, such as when dealing with ultrathin substrates, common texturization techniques can become unpractical or even unfeasible. Texturized polymer films applied on top of such devices may be used as an alternative. In this article, we report on the development of textured polydimethylsiloxane (PDMS) films to be placed on top of planar crystalline silicon solar cells based on thin substrates (=40 µ m). The PDMS polymer is deposited onto a rough surface (conventional random pyramid textured silicon), cured and detached from it. By scanning electron microscope images, we demonstrate that the dilution of PDMS into toluene helps in a better replica of the master surface. Next, we apply the optimized PDMS films on top of dummy samples based on 10, 20, and 40 µm thick crystalline silicon (c-Si) substrates whose reflectance is significantly reduced after placing the PDMS films. Accurate optical simulations indicate that the optical improvement comes from three mechanisms: higher light transmission into the device, lower reflectance at the c-Si surface, and better light trapping properties at the thin c-Si absorber. Experimental verification of the optical improvement with texturized PDMS films is reported based on 40 µ m thick solar cell, where a short-circuit current density gain of 1.7 mA/cm 2 is observed.This work was funded by MINECO from Spanish government under projects TEC2017-82305-R, ENE2016-78933-C4-1-R, ENE2017-87671-C3-2-R. The work was also supported in part by project REFER COMRDI15-1-0036 funded by ACCIÓ and the European Regional Development Fund (FEDER).Peer ReviewedPostprint (published version

2D/3D Simulations of black-silicon interdigitated back-contacted c-si(n) solar cells

Black silicon (b-Si) reduces drastically light reflectance in the front side of c-Si solar cells to values near zero for the whole absorbed solar spectrum. In this work, we apply 2D and 3D simulations to explore the efficiency limits of interdigitated back-contacted c-Si(n) solar cells with line or point contacts respectively, using ALD Al2O3 passivated b-Si in the front surface. Realistic physical and technological parameters involved in a conventional oven-based fabrication process are considered in the simulations, especially those related to surface recombination on the b-Si as well as high doped p+/n+ strip regions. One important issue is the temporal stability of surface passivation on b-Si surfaces. In this work experimental long-term b-Si surface passivation data after two years and its impact on cell performance are studied. Simulations demonstrate initial and final photovoltaic efficiencies over 24.6% and 23.2% respectively for an emitter coverage of 80% independently of the cell contact strategy. A photocurrent loss about 1.3 mA/cm2 occurs when surface recombination velocity at the b-Si surfaces degrades from 6 cm/s to a final value of 28 cm/s.Postprint (author's final draft

User's experience in the visualization of architectural images in different environments

The visualization of images, both photographic and infographic, is a process that depends on a series of features that define the user (user profile: age, sex, culture or experience, etc.), the visual message (type of image, resolution, content, quality, etc.), and the display (size, resolution, type of screen immersive or not, etc.). When we can determine how the tree features relate, the communicative messages based on visual aspects will be more efficient for both the user and the technological output. The main objective of the research work presented in this paper is to determine whether differences in the visualization (immersive or not) of specific types of images (real and virtual) related to the architecture framework, differ depending on the gender of the user. The reflection of the existence of such differences in the future will allow us to define the characteristics of the image and the medium, and maximize the emotional communication of architectural ideas, depending on the type of user.Peer ReviewedPostprint (published version

Optimization of laser processes in n+Emitter formation for c-Si solar cells

Punctual phosphorus diffused emitters were achieved by laser patterning phosphorus doped a-SiCx:H films deposited by PECVD as a doping source. Two different lasers at wavelengths of 1064 nm and 532 nm were used. Phosphorus diffusion was confirmed by Secondary Ion Mass Spectroscopy. We explored the effect of pulse energy and number of pulses per diffused point. The results show that a fine tune of the energy pulse is critical while the number of pulses has minor effects. Scanning Electron Microscopy (SEM) pictures and optical profilometry showed a laser affected area where the c-Si is melted, ejected and solidified quickly again. Typically, the diameter of the affected area for 1064 nm laser is between two and four times greater than for 532 nm laser. Optimum parameters for both lasers were determined to obtain best J-V curves nearly to ideal diode behavior. Comparing best J-V results, lower emitter saturation current density (Jo) and contact resistance are obtained with 532 nm laser. The improvement in Jo can be related mainly to the smaller affected areas observed by SEM while lower contact resistance can be attributed to that 532 nm laser has a more superficial action resulting in higher phosphorus concentration at the surface. The expected open voltage circuit for finished solar cells using these emitters is in the range of 640 mV for 532 nm laser and 620 mV for 1064 nm one.Postprint (published version

N-type emitters passivation through antireflective phosphorus doped a-SiCxNy:H(n) stacks

This paper studies the passivation of industrially textured deep silicon emitters using amorphous silicon carbonitride layers in stack configuration, deposited by plasma enhanced chemical vapor deposition. With this technique, emitter saturation current density can be decreased to values around 250 fA middot cm-2. As a consequence, open circuit voltages can be increased 25 mV achieving values around 640 mV.Postprint (published version