En la presente tesis se evalúan las propiedades ópticas y las características de emisión de luz de películas delgadas amorfas de AlN, SiN y SiC:H dopadas con Tb. La caracterización óptica se centra en la determinación del ancho de banda, la energía de Urbach y el foco de Urbach a partir de mediciones ópticas. Se desarrolla un modelo, basado en fluctuaciones térmicas de la banda, para describir la absorción fundamental sobrepuesta con las colas de Urbach. Luego, se realiza un análisis de la existencia y significado del foco de Urbach y se contrasta con modelo anterior. Uno de los principales resultados en esta parte es la capacidad del modelo antes mencionado para distinguir las regiones de Urbach y Tauc del coeficiente de absorción. En este caso, películas delgadas de a-SiC:H depositadas en distintas condiciones de dilución de hidrógeno exhibieron un ancho de banda no co...

En la presente tesis se evalúan las propiedades ópticas y las características de emisión de luz de películas delgadas amorfas de AlN, SiN y SiC:H dopadas con Tb. La caracterización óptica se centra en la determinación del ancho de banda, la energía de Urbach y el foco de Urbach a partir de mediciones ópticas. Se desarrolla un modelo, basado en fluctuaciones térmicas de la banda, para describir la absorción fundamental sobrepuesta con las colas de Urbach. Luego, se realiza un análisis de la existencia y significado del foco de Urbach y se contrasta con modelo anterior. Uno de los principales resultados en esta parte es la capacidad del modelo antes mencionado para distinguir las regiones de Urbach y Tauc del coeficiente de absorción. En este caso, películas delgadas de a-SiC:H depositadas en distintas condiciones de dilución de hidrógeno exhibieron un ancho de banda no co...

Películas delgadas amorfas semiconductoras de amplio ancho de banda del compuesto pseudobinario (SiC)1-x(AlN)x fueron depositadas por pulverización por un sistema de dos magnetrones de radio frecuencia sobre CaF2, MgO, Al2O3 y vidrio. Con el fin de determinar el ancho de banda óptico versus la composición de la película, se realizaron medidas espectroscópicas de la transmisión de donde el índice de refracción y el coeficiente de absorción fueron calculados y medidas espectroscópicas de la dispersión de energía (EDS) de donde la composición fue determinada. El ancho de banda óptico es determinado para cada composición a partir del coeficiente de absorción de dos maneras distintas: según el gráfico de Tauc y utilizando el gráfico de (αhν)2. la dependencia del ancho de banda con la composición x puede ser descrita por la ley empírica de Vegard para aleaciones.

Películas delgadas amorfas semiconductoras de amplio ancho de banda del compuesto pseudobinario (SiC)1-x(AlN)x fueron depositadas por pulverización por un sistema de dos magnetrones de radio frecuencia sobre CaF2, MgO, Al2O3 y vidrio. Con el fin de determinar el ancho de banda óptico versus la composición de la película, se realizaron medidas espectroscópicas de la transmisión de donde el índice de refracción y el coeficiente de absorción fueron calculados y medidas espectroscópicas de la dispersión de energía (EDS) de donde la composición fue determinada. El ancho de banda óptico es determinado para cada composición a partir del coeficiente de absorción de dos maneras distintas: según el gráfico de Tauc y utilizando el gráfico de (αhν)2. la dependencia del ancho de banda con la composición x puede ser descrita por la ley empírica de Vegard para aleaciones.

We develop a band-fluctuations model which describes the absorption coefficient in the fundamental absorption region for direct and indirect electronic transitions in disordered semiconductor materials. The model accurately describes both the Urbach tail and absorption edge regions observed in such materials near the mobility edge in a single equation with only three fitting parameters. An asymptotic analysis leads to the universally observed exponential tail below the bandgap energy and to the absorption edge model at zero Kelvin above it, for either direct or indirect electronic transitions. The latter feature allows the discrimination between the absorption edge and absorption tails, thus yielding more accurate bandgap values when fitting optical absorption data. We examine the general character of the model using a dimensionless joint density of states formalism with a quantitative a...

This research was funded by the Research Management Office (DGI) of the Pontificia Universidad Católica del Perú (PUCP). The authors have been supported by the PUCP under the PhD scholarship program Huiracocha (J.A. Guerra), the “Programa de repatriación” (J.A. Töfflinger), the Master scholarship (L.M. Montañez and K. Tucto) from CONCYTEC and the “Círculo de investigación” from CONCYTEC. The authors would like to thank Prof. Dr. A. R. Zanatta (IFSC-USP, Brazil) for providing access to his lab in order to perform the PL measurements and Prof. Dr. H. P. Strunk (University of Stuttgart, Germany) for helping us with the PLE measurements.

Bandgap engineering of a-SiC:H thin films was carried out to assess the material light absorption without compromising its photoelectrochemical water splitting capabilities. The tailoring was performed by varying the hydrogen concentration in the semiconductor and by post-deposition isochronical annealing treatments from 100 ?C to 700 ?C. Bandgap values were obtained by fitting the fundamental absorption region of the absorption coefficient using three different models. Differences among bandgap values extracted by these methods and its correlation with the a-SiC:H structure, demonstrate that structural features, rather than a hydrogen rearrangement or depletion, would be responsible for annealing induced optical bandgap increment. These features are taking in advantage for the bandgap engineering of a-SiC:H without changing Si-C stoichiometry. Optical bandgap values for p-doped a-SiC:H ...

The authors acknowledge funding from the Federal Ministry of Education and Research (BMBF) for funding of the Young Investigator Group Perovskite Tandem Solar Cells within the program “Materialforschung für die Energiewende” (grant no. 03SF0540), the Helmholtz Association within the HySPRINT Innovation lab project, and the HyPerCells joint Graduate School. This research was supported by the joint agreement between the DAAD (German Academic Exchange Service) and FONDECYT (National Fund for Scientific, Technological Development and Technological Innovation) under the agreements 57508544 DAAD and 423-2019-FONDECYT. Further support has been provided by the PUCP vice chancellorship for research (VRI, project no. CAP-2019-3-0041/702). The authors thank Thomas Lußky for technical support, Bor Li for part of the sample preparation, and Norbert Koch, David Cahen, Isaac Balberg and Norbert N...

We demonstrate that the modulated surface photovoltage spectroscopy (modulated SPS) technique can be applied to investigate interface states in the bandgap, i.e. interface passivation, of crystalline silicon coated with a downshift layer such as hydrogenated aluminum nitride with embedded terbium ions by suppressing straylight with a cut-off filter. Different hydrogen contents influence the surface photovoltage spectra at photon energies below the bandgap of crystalline silicon. Modulated SPS reveals that at higher hydrogen content there is a lower signal and, thus, a lower density of surface defect states. Our experiments show that modulated SPS can become a powerful tool for characterizing defect states at interfaces which cannot be easily studied by other methods. © 2021 Published under licence by IOP Publishing Ltd.

In this work, we propose a method to retrieve the thickness and optical constants of dielectric thin films from single optical transmittance measurements. The method is based on the envelope method and requires a simple dispersion model for the real part of the refractive index with few fitting parameters, while the absorption coefficient can be determined without the aid of a dispersion model. The wavelength-dependent optical constants can be obtained even from spectra that exhibit few interference fringes. We have tested the method with simulated and real transmittance data from thin films in the spectral range covering the fundamental absorption. In order to assess the method’s reliability to retrieve the optical constants and optical bandgap, a comparison is performed with the method by Chambouleyron, known as the Pointwise Unconstrained Minimization Approach, and a fit using the C...

Funding: The authors thank the Fondo Nacional de Desarrollo Científico, Tecnológico y de Inno-vación Tecnológica (PROCIENCIA-CONCYTEC), project number: 177-2020-FONDECYT (PROCIEN-CIA), project CLEAN NANOMAGNETIC. “The APC was funded by PROCIENCIA”.

This article presents the benefits of two simple analytical models for estimating the outdoor performance of three different photovoltaic technologies in Lima, Peru. The Osterwald and the constant fill factor models are implemented to estimate the maximum power delivered by three photovoltaic module technologies: aluminum back surface field, heterojunction with intrinsic thin-layer and amorphous/microcrystalline thin-film tandem. A 12-months experimental campaign is carried out through measurements of current-voltage curves, irradiance and module temperature. The results show that both models overestimate the modelled power when compared to the measured one. In order to correct the maximum power predicted by both models, a correction factor is introduced. This correction factor allows us to estimate losses and a respective effective nominal power to minimize the prediction error on a mon...

The characterization of the nominal power under real operating conditions is crucial for the correct evaluation of a photovoltaic generator. Several earlier studies proposed different methods based on empirical models for the estimation of the nominal power. These methods require experimental data obtained during optimal days under clear sky conditions and are not suitable for days deviating from these optimal conditions and, thus, generating a significant amount of noise in the data. In this sense, we propose a non-parametric statistical approach to filter out this noise to reliably estimate the real nominal power in the latter conditions. The period of study was 107 days. These were divided in two categories, clear and partly cloudy sky conditions. The results show that our statistical method allows to obtain the same nominal power under partly cloudy conditions as under clear sky. Thi...

This work presents the firsts results of the experimental characterization campaign under outdoor conditions carried out with three different photovoltaic (PV) module technologies: Standard poly-crystalline silicon (poly-Si) aluminum back surface field (Al-BSF) cells, mono-crystalline (c-Si) Heterojunction with Intrinsic Thin-Layer (HIT) cells, and amorphous and microcrystalline silicon (a-Si/µc-Si) thin-film tandem cells. We studied the behavior of these PV technologies and their performance in Lima's desertic and coastal climate during the period from May 2019 to July 2019. For this study, a new outdoor-PV laboratory was implemented at the Pontificia Universidad Católica del Perú (PUCP) with the help of the IDEA research group of the University of Jaén (UJA), Spain. The laboratory enables the characterization of PV modules by extracting the electrical parameters from the current-vo...

The nominal power of a photovoltaic system is a useful parameter in the determination of the current state of a photovoltaic generator. In the present work, the procedure proposed by Martínez-Moreno was followed, which is based on the Osterwald model. During the application of the procedure, a hysteresis effect was observed to a different extent throughout the experimental campaign. The corrected power versus irradiance values differed during the day, even when the irradiance and temperature of the module were similar. This led to an uncertainty in the inclusion of all the data. Therefore, the addition of a filter of the data is sought in the procedure of the estimation of the nominal power, as a complement to that proposed by Martinez-Moreno in an attempt to clarify the calculation in generators that presents this non-linear behavior.

The nominal power of a photovoltaic system is a useful parameter in the determination of the current state of a photovoltaic generator. In the present work, the procedure proposed by Martínez-Moreno was followed, which is based on the Osterwald model. During the application of the procedure, a hysteresis effect was observed to a different extent throughout the experimental campaign. The corrected power versus irradiance values differed during the day, even when the irradiance and temperature of the module were similar. This led to an uncertainty in the inclusion of all the data. Therefore, the addition of a filter of the data is sought in the procedure of the estimation of the nominal power, as a complement to that proposed by Martinez-Moreno in an attempt to clarify the calculation in generators that presents this non-linear behavior.

The amount of dust deposited on the surface of a panel depends on the environmental parameters. These are random (eg. humidity, wind speed and ambient temperature) which makes it difficult to model them theoretically. This paper describes the effect of dust by calculating the derating factor (η_polvo) and modeling its dependence over time. To achieve this, an experimental campaign was carried out in three tandem (a-Si / µc-Si) of 1.15 kW controlled in the city of Lima, divided into two periods of time. In the first period, from 07.15.2016 to 04.07.2017, the three strings were cleaned twice per week. The nominal power was calculated for days with clear skies conditions. It was found that between each string there are slight differences or mismatches in the nominal power, which is considered to estimate a correction factor (k) in order to readjust the output power. In the second stage fr...

The amount of dust deposited on the surface of a panel depends on the environmental parameters. These are random (eg. humidity, wind speed and ambient temperature) which makes it difficult to model them theoretically. This paper describes the effect of dust by calculating the derating factor (η_polvo) and modeling its dependence over time. To achieve this, an experimental campaign was carried out in three tandem (a-Si / µc-Si) of 1.15 kW controlled in the city of Lima, divided into two periods of time. In the first period, from 07.15.2016 to 04.07.2017, the three strings were cleaned twice per week. The nominal power was calculated for days with clear skies conditions. It was found that between each string there are slight differences or mismatches in the nominal power, which is considered to estimate a correction factor (k) in order to readjust the output power. In the second stage fr...

This paper presents the design, implementation and first results of a Photovoltaic Research Laboratory developed at the facilities of the Materials Science and Renewable Energy Group (MatER-PUCP) of the Pontifical Catholic University of Peru in collaboration with the IDEA Research Group (Research and Development in Solar Energy) of the University of Jaen (UJA), Spain. This laboratory is one of the first in the country with the appropriate equipment for calibration and certification of different commercial and emerging technologies of photovoltaic modules in the Peruvian market. The results that are expected to be obtained through an extensive experimental campaign, which began in May 2019, may be offered to companies or other public institutions, such as detailed studies of the behavior and degradation of the different technologies of photovoltaic modules depending on the particular clim...

This paper presents the design, implementation and first results of a Photovoltaic Research Laboratory developed at the facilities of the Materials Science and Renewable Energy Group (MatER-PUCP) of the Pontifical Catholic University of Peru in collaboration with the IDEA Research Group (Research and Development in Solar Energy) of the University of Jaen (UJA), Spain. This laboratory is one of the first in the country with the appropriate equipment for calibration and certification of different commercial and emerging technologies of photovoltaic modules in the Peruvian market. The results that are expected to be obtained through an extensive experimental campaign, which began in May 2019, may be offered to companies or other public institutions, such as detailed studies of the behavior and degradation of the different technologies of photovoltaic modules depending on the particular clim...