Examinando por Autor "Arredondo, Belén"

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Analysing impact of oxygen and water exposure on roll-coated organic solar cell performance using impedance spectroscopy
(Elsevier, 2018-12-28) Arredondo, Belén; Romero, Beatriz; Beliatis, MJ; del Pozo, Gonzalo; Martin-Martin, Diego; Blakesley, JC; Dibb, G; Krebs, FC; Gevorgyan, SA; Castro, Fernando
In this work we study the degradation of roll-coated flexible inverted organic solar cells in different atmospheres. We demonstrate that impedance spectroscopy is a powerful tool for elucidating degradation mechanisms; it is used here to distinguish the different degradation mechanisms due to water and oxygen. Identical cells were exposed to different accelerated degradation environments using water only, oxygen only, and both water and oxygen simultaneously, all of them enhanced with UV light. The photocurrent is dramatically reduced in the oxygen-degraded samples. Impedance measurements indicate that this phenomenon is attributed to defects introduced by absorption of oxygen, which results in an increase of the acceptor impurity (NA) at the cathode interface obtained from a Mott-Schottky analysis. Simultaneously, at the anode interface where PEDOT:PSS is not shielded by the substrate, the nature of degradation differs for the water and oxygen degraded samples. While oxygen + UV light decreases the conductivity of the PEDOT:PSS layer, water + UV light changes the PEDOT:PSS work function inducing a depletion region at the anode.
analytical evaluation of the ratio between injection and space charge limited currents in single carrier organic diodes
(IEEE, 2008) ALvarez, Angel Luis; Arredondo, Belén; Romero, Beatriz; Quintana, Xabier; Gutiérrez, Araceli; Mallavia, Ricardo; Otón, José Manuel
An analytical, complete framework to describe the current-voltage (I-V) characteristics of organic diodes without the use of previous approaches, such as injection or bulk-limited conduction is proposed. Analytical expressions to quantify the ratio between injection and space-charge-limited current from experimental I-V characteristics in organic diodes have been derived. These are used to propose a numerical model in which both bulk transport and injection mechanisms are considered simultaneously. This procedure leads to a significant reduction in computing time with respect to previous rigorous numerical models. In order to test the model, different diode structures based on two different polymers: poly(2-methoxy-5-{3',7'-dimethyloetyloxy}-p-phenylenevinylene) (MDMO-PPV) and a derivative of the poly(2,7-fluorene phenylidene) [PFP:(CN)(2)], have been fabricated. The present model is excellently fitted to experimental curves and yields the microscopic parameters that characterize the active layer.
Apuntes asignatura de Dispositivos electrónicos y circuitos
(2024-10-09) Romero Herrero, Beatriz; Arredondo, Belén; Pozo Melero, Gonzalo del; Martín, Diego
Apuntes asignatura de Tecnología Electrónica
(2024-10-09) Romero Herrero, Beatriz; Arredondo, Belén
Apuntes asignatura de Tecnología Electrónica
Colección de problemas resueltos. Dispositivos Electrónicos y Circuitos
(2024-10-09) Romero Herrero, Beatriz; Arredondo, Belén
Exact analytical solution of a two diode circuit model for organic solar cells showing S-shape using Lambert W-functions
(Exact analytical solution of a two diode circuit model for organic solar cells showing S-shape using Lambert W-functions, 2012) Romero, Beatriz; Pozo, Gonzalo del; Arredondo, Belén
Organic solar cells (OSCs) often show a kink, also called S-shape, in the current-voltage (I-V) characteristics, that has been attributed to different physical phenomena such as poor quality of cathode-active layer interface or unbalance charge carrier mobilities. This non-ideal behaviour can be electrically modelled including a second diode, in reverse bias, together with an extra shunt resistance (R-P2) in the traditional solar cell equivalent circuit. In this paper, we solve without approximations the transcendental equation system derived from this modified circuit. We have obtained an analytical expression for I-V curves decoupling the voltage drop in each diode using Lambert W function. This expression has been fitted to experimental data in order to obtain circuital parameters. Simulations varying saturation current of reverse diode (I-02) and R-P2 have been performed in order to study the dependence of S-shape with these parameters.
Extraction of circuital parameters of organic solar cells using the exact solution based on Lambert W-function
(SPIE, 2012) Pozo, Gonzalo del; Romero, Beatriz; Arredondo, Belén
he electrical behavior of organic solar cell (OSC) has been analyzed using a simple circuital model consisting on an ideal diode together with a series and parallel resistances (R-S and R-P respectively). Applying Kirchhoff's Laws to the circuit leads to a transcendental equation that can be solved numerically without approximations using the Lambert W function. Theoretical expression has been fitted to experimental current-voltage (I-V) curves under forward bias, obtaining fairly accurate values for the electrical parameters. This model has been validated comparing the extracted parameters for dark and illumination conditions of different devices. Results show good agreement for R-S, and ideality factor eta. Electrical parameters obtained in this work are also compared to those ones extracted using an approximated method often employed by other authors (1). We conclude that approximated method leads to reasonable good values for R-S, R-P and. However, in the case of Rp the voltage range chosen to fit the data with the exact method must be constrained to the fourth quadrant, where the role of parallel resistance is more critical. To validate the model, a bunch of organic solar cells with structure ITO/ poly(3,4-ethylenedioxythiophene)-poly (4-styrene sulfonate (PEDOT:PSS)/ poly(3-hexylthiophene) (P3HT): 1-(3-methoxycarbonyl)-propyl-1-1-phenyl-(6,6) C61 (PCBM)/Al has been fabricated in inert atmosphere. Different active layers were deposited varying the P3HT: PCBM ratio (1:0.64, 1:1, 1:1.55) and the active layer thickness ( ranging from 100 to 280 nm). Devices are encapsulated inside the glove-box prior its characterization outside the glove-box. Electro optical characterization has been performed with a halogen lamp. Values extracted for RS range from 142 Omega to 273 Omega, values for R-P range from 25 k Omega to 331 k Omega. Ideality factor ranges from 5 to 17.
Guía asignatura de Tecnología Electrónica
(2024-10-09) Romero Herrero, Beatriz; Arredondo, Belén
High stable CsFAPbIBr perovskite solar cells with dominant bulk recombination at real operating temperatures
(Royal Society of Chemistry, 2023-05-02) Romero, Beatriz; Delgado, silvia; Glowienka; Chang, Cheng-Tsung; del Pozo, Gonzalo; Arredondo, Belén; Martin-Martin, Diego; Contreras, Pedro; Galagan, Yulia
Mixed-cation mixed-halide perovskite solar cells have been characterized in DC at different temperatures (from -20 degrees C up to 50 degrees C) and the time evolution of the device efficiency has been assessed using different degradation protocols (indoors and outdoors). The completely planar p-i-n structure is ITO/CuNiOx/PTAA/CsFAPbIBr/PCBM/PEI/Ag. Pristine current-voltage characteristics barely show hysteresis, at any temperature. Open circuit voltage decreases with temperature at a rate of -1.5 mV degrees C-1, and the obtained PCE temperature coefficient is lower than -0.001% K-1, which is an outstanding value for this emerging photovoltaic technology. Cells have been degraded under different protocols: indoors using different light/dark cycles and outdoors in a high temperature and high irradiation location. Cells show no significant decrease of the efficiency after more than 350 h of indoor light cycling and the estimated T-80 obtained for the sample degraded outdoors under high irradiation and high temperature conditions is similar to 15 days.
High-bandwidth organic photodetector analyzed by impedance spectroscopy
(IEEE, 2012) Arredondo, Belén; Dios, Cristina de; Vergaz, Ricardo; Pozo, Gonzalo del; Romero, Beatriz
An organic bulk heterojunction photodetector (OPD) is fabricated on the basis of a blend of poly(3-hexyl thiophene):1-(3-methoxycarbonyl)-propyl-1-1-phenyl-(6,6) C61. The OPD responsivity is calculated from current density-voltage characteristic (J-V) under green-LED illumination obtaining 1 A/W. Frequency response at different biases is measured, which shows a high ¿3-dB cutoff frequency of 343 kHz at ¿3 V. Impedance measurements are carried out at different reverse biases, and the results are fitted with a small signal equivalent circuit. The device cutoff frequency (fc) can be estimated with the parameters extracted from this circuit obtaining good agreement between measured and calculated fc.
Identification of Degradation Mechanisms in Slot-Die-Coated Nonfullerene ITO-Free Organic Solar Cells Using Different Illumination Spectra
(ACS, 2020-07-27) Arredondo, Belén; del Pozo, Gonzalo; Hernández-Balaguera, Enrique; Martin-Martin, Diego; López-Gonzalez, Maria del Carmen; Romero, Beatriz; Lopez-Fraguas, Eduardo; Vergaz, Rcardo; Quintana, Xabier; Lamminaho, Jani; Destouesse, Elodie; Ahmadpour, Mehrdad; Turkovic, Vida; Madsen, Morten
In this work, we have studied degradation mechanisms of nonfullerene-based organic solar cells with PET/Ag/ZnO/ PBDTB-T:ITIC/PEDOT:PSS/CPP PEDOT:PSS device structure. We compare pristine and degraded samples that were subjected to outdoor degradation following the standard ISOS-O2 protocol. The ideality factors for different incident wavelengths obtained from open-circuit voltage vs irradiation level and current density-voltage (J-V) measurements at different temperatures indicate that for aged samples recombination is governed by the Shockley-Read-Hall mechanism occurring in a region near the anode. Samples were also characterized using impedance spectroscopy (IS) and fitted to an electrical model. Impedance parameters were used to obtain mobility, indicating a clear degradation of the active layer blend for aged samples. The change in the chemical capacitance also reveals a worsening in carrier extraction. Finally, two-dimensional (2D) numerical simulations and fits to experimental J-V curves confirm the existence of a layer near the anode contact with poorer mobility and a decrease in the anode work function (WF) for the degraded samples.
Influence of electrical operating conditions and active layer thickness on electroluminescence degradation in polyfluorene-phenylene based light emitting diodes
(Elsevier, 2009) Romero, Beatriz; Arredondo, Belén; Alvarez, Angel Luis; Mallavia, Ricardo; Salinas, A; Quintana, Xabier; O, José Manuel
We have studied the influence of the electrical working conditions (voltage or current biased). and the active layer thickness on electroluminescence (EL) properties of polymeric light emitting diodes based on poly-[9,9-bis(6'-cyanohexyl)-2,7-fluorene-alt-co-1,4-phenylene], [PFP:(CN)(2)]. Diodes with different active layer thicknesses (55-140 nm) have been fabricated and characterized. Temporal evolution of the spectra at constant bias and current, as well as the spectral evolution with the current, has been performed. Excitation photoluminescence has been used to discriminate between intrinsic and defect-related transitions. The relative spectral area arising from defects has been quantified by means of Gaussian deconvolution for different device excitations. Active layer thickness has been observed to play an important role on the emissive spectral shape. In thick samples EL tends to resemble fluorescence from the pristine material. In contrast, thinner samples clearly show two additional bands related to defects: the first one is structured in the range 470-510 nm, which is proposed to be due to electron accumulation in the active layer, and a second band at 535 nm. arising from on-chain keto defects due to the presence of oxygen. The role of the electron blocking character of the PEDOT:PSS on the spectral shape, as well as the influence of the active layer thickness on the oxygen concentration, are discussed
Influence of solvent additive on the performance and aging behavior of non-fullerene organic solar cells
(Elsevier, 2022) Arredondo, Belén; Pérez-Martínez, José Carlos; Muñoz-Díaz, Laura; López-González, Maria del Carmen; Martín-Martín, Diego; Pozo, Gonzalo del; Hernández-Balaguera, Enrique; Romero, Beatriz; Lamminaho, Jani; Turkovic, Vida; Madsen, Morten
The performance of organic solar cells has improved significantly in recent years due to the use of non-fullerene acceptors (NFA). While processing additives are typically added to the active layer blends to enhance device performance in NFA organic solar cells, their impact on device degradation remains unclear. In this work we have compared the performance, in pristine and degraded state, between air-processed slot-die coated NFA ITOfree organic solar cells with and without the processing additive DIO, using a structure of PET/Ag/ZnO/PBDB-T: ITIC/FHC PEDOT:PSS. We observed an improvement in the power conversion efficiency of the devices when adding DIO, from 4.03% up to 4.97%. The evolution of the performance for both devices under ISOS-L1 life testing protocol reveals that the drop in efficiency is mainly due to a decay of JSC for both cells. In the short time scale the efficiency of non-DIO cells decays faster than the DIO cells, whereas in the long time scale the efficiency of non-DIO cells tends to stabilize sooner. Carrier mobilities estimated from impedance measurements decrease with time at similar rate for both degraded samples. Besides, DIO devices present a steep increase of the series resistance with time causing a decrease of the FF and thus of the efficiency. Moreover, in both degraded devices, the open-circuit voltage saturates with increasing illumination intensity. Numerical simulations reveal that a reduced anode work function of 5 eV is needed to fit experimental data.
On the electrical degradation and green band formation in alpha- and beta-phase poly(9,9-dioctyfluorene) polymer light-emitting diodes
(Elsevier, 2011) Arredondo, Belén; Romero, Beatriz; Gutiérrez, Araceli; Martínez, Armando; Alvarez, Angel Luis; Quintana, Xabier; Otón, José Manuel
In this work we report a detailed comparison of optical and electrical degradation between alpha- and beta-phase poly(9,9-dioctyfluorene) (PFO) based diodes. Analysis of the EL spectra along continuous operation time in alpha- and beta-PFO based diodes reveals that the unwanted green emission traditionally associated to fluorenone is more likely to occur in a-phase PFO. The relative spectral areas arising from excitonic and vibronic transitions as well as fluorenone defects have been quantified by means of Gaussian deconvolution along the operation time. The relative spectral area associated to the formation of the fluorenone increases 13% for the beta-PFO diode and up to 21% for the alpha-PFO diode only after 35 min of continuous operation. Analysis of the I-V curve before and after electrical stressing has lead to hole mobilities in pristine diodes of 1.4 x 10(-4) cm(2)/Vs and 1.6 x 10(-5) cm(2)/Vs for beta-PFO and alpha-PFO respectively. Both beta-PFO and alpha-PFO degraded samples show a reduction in the hole mobility, as well as an increase in the width of the Gaussian density of states.
Performance of ITO-free inverted organic bulk heterojunction photodetectors: Comparison with standard device architecture
(Elsevier, 2013) Arredondo, Belén; Dios, Cristina de; Vergaz, Ricardo; Romero, Beatriz; Zimmermann, Birger; Wurfel, Uli
We report on the fabrication of Indium Tin Oxide (ITO)-free inverted organic bulk heterojunction (BHJ) photodetectors of poly(3-hexylthiophene) (P3HT): 1-(3-methoxycarbonyl)propyl-1-1-phenyl-(6,6) C61 (PCBM). The final inverted device structure is Cr/Al/Cr/P3HT:PCBM/poly-3,4-ethylenedioxythiophene:poly-styrenesulfonate (PEDOT:PSS)/Ag (Zimmermann et al., 2009) [1]. The device is top-absorbing with the light entering through the hole contact grid. We have fabricated standard devices with structure ITO/PEDOT:PSS/P3HT:PCBM/LiF/Al in order to carry out a comparison study. Inverted photodetectors show slightly higher quantum efficiency and responsivity compared to standard devices. Frequency responses at different bias voltages were measured showing a maximum -3 dB cut-off frequency of 780 kHz and 700 kHz at -3 V for the standard and inverted structures respectively. Parameters extracted from the fit of a circuital model to the impedance spectroscopy measurements were used to estimate the photodiode cut-off frequency as function of bias. (C) 2013 Elsevier B.V. All rights reserved.
Problemas asignatura de Tecnología Electrónica
(2024-10-09) Romero Herrero, Beatriz; Arredondo, Belén
A project-oriented integral curriculum on Electronics for Telecommunication Engineers
(IEEE, 2010-04-14) Machado, Felipe; Malpica, Norberto; Vaquero, Joaquín; Arredondo, Belén; Borromeo, Susana
This paper describes the Electronics curriculum in the Telecommunication Engineer degree at Rey Juan Carlos University (URJC) in Spain. Telecommunication Engineering started in the 2003-2004 academic year. In these years, all the electronic courses have been set up with a main practical orientation and with Project Based Learning (PBL) activities, both compulsory and voluntary. Once these courses have been successfully implemented we have reoriented some of the practical activities to be more interlaced. In this sense, projects involving students of different courses have been developed, as well as projects involving students from different years. All these activities fit in the principles promulgated by the Declaration of Bologna, which results in the actual updating of the university degree structure in Spain.
Temperature behaviour of mixed-cation mixed-halide perovskite solar cells. Analysis of recombination mechanisms and ion migration
(Elsevier, 2023) López-González, Mari Carmen; Pozo, Gonzalo del; Arredondo, Belén; Delgado, Silvia; Martín-Martín, Diego; García-Pardo, Marina; Romero, Beatriz
In our study, we show that compositional engineering of the “A” site cation of ABX3 perovskite structure formed by a mix of organic and inorganic cations is an effective route to improve the thermal stability of perovskite solar cells (PSCs). In this work, mixed-cation mixed-halide PSCs have been fabricated and characterized with temperature, from 253 up to 333 K. The active layer based on CsRbFAMAPb(IBr)3 results in a more stable device compared to standard MAPbI3 devices. Electrical characterization reveals a decrease of the solar cell parameters with temperature. Using Impedance Spectroscopy (IS) characterization, we have estimated an activation energy for the halide ion migration of 0.63 ± 0.08 eV, an ion diffusion coefficient of 10− 14 cm2 s − 1 , and a defect density of 7.27⋅1015 cm− 3 . To our knowledge, this is the first time that these parameters have been calculated in CsRbFAMAPb(IBr)3 based devices, resulting in improved values compared to MAPbI3 devices. The worsening of device performance for temperatures above 300 K is attributed to a decrease of the spiro-OMeTAD conductivity and the degradation of the perovskite/spiro-OMeTAD interface. It is shown that for low temperatures (from 253 to 323 K), Shockley-Red-Hall (SRH) recombination in the bulk governs, while for temperatures above 323 K the increase in surface recombination becomes dominant due to the presence of non-selective contacts. Numerical simulations using SILVACO ATLAS corroborate the role of SRH in the perovskite active layer for low and medium temperatures, and the crucial influence of spiro-OMeTAD transport properties in the device performance parameters.
Visible Light Communication System using an organic bulk heterojunction photodetector
(MDPI AG, 2013) Arredondo, Belén; Romero, Beatriz; Sánchez-Pena, José Manuel; Fernández-Pacheco, Agustin; Alonso, Eduardo; Vergaz, Ricardo; Dios, Cristina de
A visible light communication (VLC) system using an organic bulk heterojunction photodetector (OPD) is presented. The system has been successfully proven indoors with an audio signal. The emitter consists of three commercial high-power white LEDs connected in parallel. The receiver is based on an organic photodetector having as active layer a blend of poly(3-hexylthiophene) (P3HT) and phenyl C61-butyric acid methyl ester (PCBM). The OPD is opto-electrically characterized, showing a responsivity of 0.18 A/W and a modulation response of 790 kHz at -6 V.
Visible Light Communication system using an organic emitter and a perovskite photodetector
(Elsevier, 2019-10-01) Lopez-Fraguas, Eduardo; Arredondo, Belén; Vega-Colado, Cesar; del Pozo, Gonzalo; Najafi, Mehrdad; Martin-Martin, Diego; Galagan, Yulia; Sanchez-Pena, José Manuel; Vergaz, Rcardo; Romero, Beatriz
The past few years have seen a great increase in the development of Visible Light Communication systems (VLC), mainly triggered by the wide variety of situations they can be used in. These communication systems have traditionally employed inorganic light emitters and photodetectors. In this work, we present a VLC system using an organic emitter and a perovskite photodetector, both fabricated using low cost processing techniques. Perovskite devices have been widely studied as photovoltaics cells since they have achieved great efficiencies, and, in the recent years, there is also an intense research of these devices as photodetectors. In this work, we have fabricated and characterized a perovskite photodetector with layer structure ITO/PTAA/Perovskite/PCBM/ BCP/Cu, and integrated it in a visible communication system to successfully link an audio signal.