Apuntes de electricidad y óptica (I): electromagnetismo

zip comprimit. Pàgina inicial: 141/index.htm[cat] Aquesta pàgina web és utilitzada com text guia del pla docent de l'assignatura Electricitat i Òptica dintre dels estudis de la llicenciatura de química. S'aborden els següents temes: càrregues i camp elèctric, potencial elèctric, conductors, corrent elèctric, magnetisme, inducció electromagnètica, equacions de Maxwell i ones electromagnètiques.[spa] Esta página web es utilizada como texto guía del plan docente de la asignatura Electricidad y Óptica dentro de los estudios de la licenciatura de química. Se abordan los siguientes temas: carga y campo eléctrico, potencial eléctrico, conductores, corriente eléctrica, magnetismo, inducción electromagnética, ecuaciones de Maxwell y ondas electromagnéticas

Spectral analysis of the angular distribution function of back reflectors for thin film silicon solar cells

Nowadays, one of the most important challenges to enhance the efficiency of thin film silicon solar cells is to increase the short circuit intensity by means of optical confinement methods, such as textured back-reflector structures. In this work, two possible textured structures to be used as back reflectors for n-i-p solar cells have been optically analyzed and compared to a smooth one by using a system which is able to measure the angular distribution function (ADF) of the scattered light in a wide spectral range (350-1000 nm). The accurate analysis of the ADF data corresponding to the reflector structures and to the μc-Si:H films deposited onto them allows the optical losses due to the reflector absorption and its effectiveness in increasing light absorption in the μc-Si:H layer, mainly at long wavelengths, to be quantified

Poly(amidoamine) Dendrimer as an Interfacial Dipole Modification in Crystalline Silicon Solar Cells

Poly(amidoamine) (PAMAM) dendrimers are used to modify the interface of metal-semiconductor junctions. The large number of protonated amines contributes to the formation of a dipole layer, which finally serves to form electron selective contacts in silicon heterojunction solar cells. By modifying the work function of the contacts, the addition of the PAMAM dendrimer interlayer quenches Fermi level pinning, thus creating an ohmic contact between the metal and the semiconductor. This is supported by the observation of a low contact resistivity of 4.5 mΩ cm2, the shift in work function, and the n-type behavior of PAMAM dendrimer films on the surface of crystalline silicon. A silicon heterojunction solar cell containing the PAMAM dendrimer interlayer is presented, which achieved a power conversion efficiency of 14.5%, an increase of 8.3% over the reference device without the dipole interlayer

Ultrathin a-Si:H/Oxide transparent solar cells exhibiting UV-Blue selective-like absorption

This is the peer reviewed version of the following article: Lopez-Garcia, A. [et al.]. Ultrathin a-Si:H/Oxide transparent solar cells exhibiting UV-Blue selective-like absorption. "Solar RRL", April 2023, which has been published in final form at https://onlinelibrary.wiley.com/doi/10.1002/solr.202200928. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.Herein, the fabrication of transparent solar cells based on nanometric (8 and30 nm) intrinsic hydrogenated amorphous siliconfilms (a-Si:H) and using oxidethinfilms as transparent carrier selective contacts are reported. The ultrathindevices present photovoltaic effect and high average visible transmittance (AVT).Additionally, they display a shifted spectral response toward short wavelengths.Glass/fluorine-doped tin oxide (FTO)/aluminum-doped zinc oxide (AZO)/a-Si:H/MoO3/indium tin oxide (ITO) prototypes are shown, presenting AVT=35% andphotovoltaic conversion efficiency (PCE)=2% for a device with a 30 nm a-Si:Hfilm. This yields a light utilization efficiency (LUE) of 0.7%, a record up to this datefor inorganic oxide-based transparent solar cells. For devices including an 8 nma-Si:Hfilm, the AVT reaches 66% with a PCE=0.6% (LUE=0.4%). These highAVT values are comparable or even superior in some cases to those achieved forpure oxide devices. Thesefindings confirm the potential of the proposedarchitectures for the development of highly transparent energy harvesters asfunctional components in building-integrated photovoltaics (BIPV), agrophoto-voltaics (APV), sensors and other low-power devices. In addition, these devicesare fabricated with earth-abundant materials and with up-scalable techniquesthat can allow for a feasible implementation.Peer ReviewedPostprint (published version

Influence of Co-Sputtered Ag:Al Ultra-Thin Layers in Transparent V2O5/Ag:Al/AZO Hole-Selective Electrodes for Silicon Solar Cells

As optoelectronic devices continue to improve, control over film thickness has become crucial, especially in applications that require ultra-thin films. A variety of undesired effects may arise depending on the specific growth mechanism of each material, for instance a percolation threshold thickness is present in Volmer-Webber growth of materials such as silver. In this paper, we explore the introduction of aluminum in silver films as a mechanism to grow ultrathin metallic films of high transparency and low sheet resistance, suitable for many optoelectronic applications. Furthermore, we implemented such ultra-thin metallic films in Dielectric/Metal/Dielectric (DMD) structures based on Aluminum-doped Zinc Oxide (AZO) as the dielectric with an ultra-thin silver aluminum (Ag:Al) metallic interlayer. The multilayer structures were deposited by magnetron sputtering, which offers an industrial advantage and superior reliability over thermally evaporated DMDs. Finally, we tested the optimized DMD structures as a front contact for n-type silicon solar cells by introducing a hole-selective vanadium pentoxide (V2O5) dielectric layer

Hot wire chemical vapor deposition: limits and opportunities of protecting the tungsten catalyzer from silicide with a cavity

Hot Wire Chemical Vapor Deposition (HW-CVD) is one of the most promising techniques for depositing the intrinsic microcrystalline silicon layer for the production of micro-morph solar cells. However, the silicide formation at the colder ends of the tungsten wire drastically reduces the lifetime of the catalyzer, thus limiting its industrial exploitation. A simple but interesting strategy to decrease the silicide formation is to hide the electrical contacts of the catalyzer in a long narrow cavity which reduces the probability of the silane molecules to reach the colder ends of the wire. In this paper, the working mechanism of the cavity is elucidated. Measurements of the thickness profile of the silicon deposited in the internal walls of the cavity have been compared with those predicted using a simple diffusion model based on the assumption of Knudsen flow. A lifetime study of the protected and unprotected wires has been carried out. The different mechanisms which determine the deterioration of the catalyzer have been identified and discussed

Deoxyribonucleic acid-based electron selective contact for crystalline silicon solar cells

This is the peer reviewed version of the following article: Tom, T. [et al.]. Deoxyribonucleic acid-based electron selective contact for crystalline silicon solar cells. "Advanced materials technologies (Weinheim)" [en línia], 18 Octubre 2022, [Consulta: 12 Desembre 2022]. Disponible a: http://hdl.handle.net/2117/377832, which has been published in final form at https://onlinelibrary.wiley.com/doi/10.1002/admt.202200936. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.Development of carrier selective contacts for crystalline silicon solar cells has been recently of great interest toward the further expansion of silicon photovoltaics. The use of new electron and hole selective layers has opened an array of possibilities due to the low-cost processing and non-doping contacts. Here, a non-doped heterojunction silicon solar cell without the use of any intrinsic amorphous silicon is fabricated using Deoxyribonucleic acid (DNA) as the electron transport layer (ETL) and transition metal oxide V2O5 as the hole transport layer (HTL). The deposition and characterization of the DNA films on crystalline silicon have been studied, the films have shown a n-type behavior with a work function of 3.42 eV and a contact resistance of 28 mO cm2. This non-doped architecture has demonstrated a power conversion efficiency of 15.6%, which supposes an increase of more than 9% with respect to the cell not containing the biomolecule, thus paving the way for a future role of nucleic acids as ETLs.T.T. and E.R. shared co-first authorship. This research was supported by Spanish government through grants PID2019-109215RB-C41, PID2019-109215RB-C43, and PID2020-116719RB-C41 funded by MCIN/ AEI/10.13039/501100011033. One of the authors (T.T.) acknowledges the support of the Secretaria d’Universitats i Recerca de la Generalitat de Catalunya and European Social Fund (2019 FI_B 00456). Besides this, the authors thank technical staff from Barcelona Research Center in Multiscale Science and Engineering from Universitat Politècnica de Catalunya for its expertise and helpful discussions over XPS results, Dr. Oriol Arteaga Barriel from Universitat de Barcelona for the thickness measurements, and also Guillaume Sauthier from Catalan Institute of Nanoscience and Nanotechnology for his contribution through UPS measurements and discussions.Peer ReviewedPostprint (published version

Main properties of Al2O3 thin films deposited by magnetron sputtering of an Al2O3 ceramic target at different radio-frequency power and argon pressure and their passivation effect on p-type c-Si wafers

In this work, 50-nm thick Al2O3 thin films were deposited at room temperature by magnetron sputtering from an Al2O3 ceramic target at different RF power and argon pressure values. The sputtering technique could be preferred to conventional atomic layer deposition for an industrial application, owing to its simplicity, availability, and higher deposition rate. The resulting thin films were characterized by UV/Vis/NIR spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The deposited Al2O3 material was always highly transparent and amorphous in nature. It was found that the O/Al ratio is higher when the Al2O3 layer is deposited at lower RF power or higher argon pressure. Also, some argon incorporation into the films was observed at low deposition pressure. On the other hand, the performance of the previously characterized Al2O3 thin films in the passivation of 2.25-Ωcm p-type float zone c-Si wafer surfaces was evaluated by the quasi-steady-state photoconductance technique. The best effective carrier lifetime value at one-sun illumination, 0.34 ms (corresponding to a surface recombination velocity of 41 cm/s), was obtained with the 50-nm Al2O3 deposited at the higher argon pressure studied, 0.67 Pa (5.0 mTorr), with the lowest RF power studied, 150 W (corresponding to a power density of 3.3 W/cm2), and after an annealing process, in this case at 350ºC for 20 min with forming gas. It was assumed that the reduction of the surface passivation quality at higher RF power or lower argon pressure is a consequence of an increased surface damage, and, probably, to a decrease of the O/Al ratio of the Al2O3 passivation material. These assumptions were confirmed with the obtainment of a lifetime of 0.73 ms (a surface recombination velocity equal to 19 cm/s) with a simple experiment with Al2O3 deposited with progressively varied sputtering conditions started from minimal silicon surface damage conditions: 50 W (corresponding to a power density of 1.1 W/cm2) and 6.67 Pa (50 mTorr). Finally, comments about further improvement of the effective lifetime (up to 1.25 ms, corresponding to a surface recombination velocity of 11 cm/s) with preliminary experiments about the incorporation of an intrinsic hydrogenated amorphous silicon interlayer are included

PEN as substrate for new solar cell technologies

The possible use of polyethylene naphthalate as substrate for low-temperature deposited solar cells has been studied in this paper. The transparency of this polymer makes it a candidate to be used in both substrate and superstrate configurations. ZnO:Al has been deposited at room temperature on top of PEN. The resulting structure PEN/ZnO:Al presented good optical and electrical properties. PEN has been successfully textured (nanometer and micrometer random roughness) using hot-embossing lithography. Reflector structures have been built depositing Ag and ZnO:Al on top of the stamped polymer. The deposition of these layers did not affect the final roughness of the whole. The reflector structure has been morphologically and optically analysed to verify its suitability to be used in solar cells

Does Sb2Se3 admit nonstoichiometric conditions? How modifying the overall se content affects the structural, optical, and optoelectronic properties of Sb2Se3 thin films

Sb2Se3 is a quasi-one-dimensional (1D) semiconductor, which has shown great promise in photovoltaics. However, its performance is currently limited by a high Voc deficit. Therefore, it is necessary to explore new strategies to minimize the formation of intrinsic defects and thus unlock the absorber’s whole potential. It has been reported that tuning the Se/Sb relative content could enable a selective control of the defects. Furthermore, recent experimental evidence has shown that moderate Se excess enhances the photovoltaic performance; however, it is not yet clear whether this excess has been incorporated into the structure. In this work, a series of Sb2Se3 thin films have been prepared imposing different nominal compositions (from Sb-rich to Se-rich) and then have been thoroughly characterized using compositional, structural, and optical analysis techniques. Hence, it is shown that Sb2Se3 does not allow an extended range of nonstoichiometric conditions. Instead, any Sb or Se excesses are compensated in the form of secondary phases. Also, a correlation has been found between operating under Se-rich conditions and an improvement in the crystalline orientation, which is likely related to the formation of a MoSe2 phase in the back interface. Finally, this study shows new utilities of Raman, X-ray diffraction, and photothermal deflection spectroscopy combination techniques to examine the structural properties of Sb2Se3, especially how well-oriented the material is.Postprint (published version