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The highest efficiencies in single-junction solar cells are obtained with devices based on GaAs. As this material is reaching the limit in material quality, the optimization of the design of the cell becomes more important. In this study we implement a patterning technique to the bottom contact layer of thin-film GaAs solar cells that increases the reflectance of photons to the active layers. Both shallow junction and deep junction devices were evaluated, and for deep junction cells, both the short circuit current and the open circuit voltage increase with the reflectance. The radiative saturation current density also decreases, indicating increased photon recycling. Detailed model simulations are performed to further evaluate the mechanisms leading to the improved performance of the deep junction design. Based on the same model, the possibilities for further improvements utilizing the deep junction are also identified.

The study presents a theoretical investigation of the impact of individual electron and hole dynamics on the photovoltaic characteristics of InAs/GaAs quantum dot solar cells. The analysis is carried out by exploiting a model which includes a detailed description of quantum dots (QD) kinetics within a drift-diffusion formalism. Steady-state and transient simulations show that hole thermal spreading across the closely spaced QD valence band states allows to extract the maximum achievable photocurrent from the QDs; on the other hand, slow hole dynamics turns QDs into efficient traps, impairing the short circuit current despite the extended light harvesting provided by the QDs.

This paper presents a device-level model of quantum dot (QD) solar cells, coupling the classical drift-diffusion equations for transport of bulk carriers with a set of rate equations describing the QD carrier dynamics. The model is applied to carry out a detailed study of the impact of thermal-assisted processes on the electrical performance of InAs/GaAs QD solar cells (QDSCs), by exploiting experimentally determined parameters for QD photogeneration and carrier kinetics. Special emphasis is given on the analysis of the open circuit voltage degradation, as well as its dependence on QD size and carrier lifetime. The modeling approach is validated by comparing simulated trends against experimental data in the literature.

This paper presents a theoretical study about quantum dot solar cells by means of numerical simulations, considering different doping levels in the intrinsic region of the cells, with the aim of evaluating the effect on the device's power conversion efficiency. Results of simulations performed over GaAs solar cells with InAs quantum dots, based on two different fabrication processes, are reported. The donor doping density in the intrinsic region was ranged from 1013 to 1017 cm-3. It is shown that, for a doping level of 7×1015 cm-3, the contribution of larger sized quantum dots to the photocurrent is increased by 50%, a very promising result in the search for new designs with higher efficiencies. Fil: Cedola, Ariel Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Ingeniería. Departamento de Electrotecnia. Grupo de Est.s/materiales y Disposit.electronicos; Argentina Fil: Gioannini, Mariangela. Politecnico di Torino; Italia Fil: Cappelluti, Federica. Politecnico di Torino; Italia Fil: Cappelletti, Marcelo Ángel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Ingeniería. Departamento de Electrotecnia. Grupo de Est.s/materiales y Disposit.electronicos; Argentina Fil: Peltzer y Blanca, Eitel Leopoldo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Ingeniería. Departamento de Electrotecnia. Grupo de Est.s/materiales y Disposit.electronicos; Argentina

The performance of crystalline silicon n + / p / p + and n / n / p + solar cells under AM0 spectrum,irradiated with 1 MeV electrons at fluences below 10 17 cm −2 has been analyzed by means ofcomputer simulation. The software used, fully developed by the authors, solves numerically inone dimension under steady-state conditions, the Poisson and continuity equationsself-consistently. The influence of constructive characteristics and different levels of hazardousenvironmental work conditions on the maximum power point of over 150 devices has beeninvestigated. The study has allowed the authors to propose a useful analytical model related tothe constructive characteristics of the device such as polarity, base resistivity and totalthickness, with the aim of examining the electrical performance of Si space solar cells. Resultspresented in this paper are important in order to contribute to the design of radiation-hardeneddevices. 1. Introduction Taking into account the urgent need to make the most ofalternative energy sources, the study of semiconductor devicesthatcanprovidepoweratlowoperatingcost,suchassolarcells,is extremely important at the present time. Deep studies aboutso-calledthirdgenerationsolarcells,focusedonnewmaterialsand technologies such as intermediate band, quantum dots andhot-carrier devices [1–4], are being carried out with the aimof reducing the cost and increasing the efficiency with respectto the first generation, i.e. crystalline silicon (c-Si) solar cells.However, in present times a considerable amount of researchin the field of the photovoltaic cells is still dominated by theconventional c-Si devices.For space power applications, where the devices areexposed to irradiation of high energy particles, multijunction(MJ) solar cells based on III–V technologies havedemonstrated higher conversion efficiencies and radiation-resistance than c-Si devices [5–7]. Nevertheless, c-Si solarcells have proven to offer a worthy operational reliability andcosteffectivenessasaspacepowersource[8–10]andthereforefurther research in this topic is still required.Every different solar cell structure from a given material,total thickness, base resistivity and polarity (p- or n-type),is expected to respond differently as a function of radiation.Therefore, each device must undergo some kind of irradiationtest to determine the degradation characteristics. Nowadays,precise techniques of modeling and simulation have becomefundamental tools to predict and to improve the responseof electronic devices under different operation conditions,offering valuable knowledge at a much lower cost and in lesstime than experimentation.In order to contribute to the design of radiation-hardeneddevices, this paper presents a theoretical study of the behaviorof different c-Si n

In the present work, a complete numerical analysis of the influence of deep-trap levels on the dark current of silicon PIN photodiodes under 1 MeV neutron radiation was done. Results corroborate that energy levels near the mid-gap affect to a great extent the dark current. Radiation tolerances of undoped and gold-doped devices were compared through simulations. It has been concluded that gold in silicon reduces the neutron-induced damage. Finally, a model to calculate the dark current of irradiated devices doped with deep-impurities is presented.

This work focuses on study of radiation induced displacement damage effects on silicon PIN photodiodes at both, dark and illumination conditions, by mean of numerical simulations. For fluences greater than a certain limiting value, relation between photocurrent and dark current decreases below ten, leading to an undesirable device operation. An iterative method is proposed for design optimization of PIN photodiodes to be used under irradiation, that minimize radiation effects on total reverse current and maximize device response to incident light.

The experimental evolution of the threshold voltage of MOS devices during irradiation at changing bias voltages, exhibiting charging and neutralization of the oxide traps, was well fitted by a two-traps dynamic balance model. The values and field dependence of the extracted physical parameters are in close agreement with previously reported ones.

In the present work, the influence of deep-trap levels on the dark current of silicon PIN photodiodes under 1 MeV neutron radiation has been investigated by means of a complete numerical analysis. The computational code used for simulations, developed by the authors, numerically solves the coupled Poisson and continuity equations on a 2D domain to obtain the behavior of electronic devices. Recombination through deep levels in the bandgap is described by the Shockley–Read–Hall (SRH) theory. Defects caused by radiation are quantified in terms of the damage coefficient K for the minority carrier lifetime. The effects of the radiation studied are atomic displacement damages. Results corroborate that the dark current is strongly affected by energy levels close to the midgap. A relationship between the current damage rate and the trap level location in the silicon bandgap was obtained. A model to calculate the dark current of irradiated devices doped with deep impurities is presented. Simulations have allowed the comparison of radiation tolerances of undoped and gold-doped devices. The higher gold density has shown a marked improvement of the hardness of the devices to radiation effects.

A computer program for the simulation of semiconductor devices has been developed and applied to the analysis of radiation effects on Si PIN photodiodes. The study has allowed the authors to propose useful analytical models related to such optical and electrical device parameters as peak spectral response and dark current. Peak spectral response has shown a marked dependence on device layers dimensions. Dark current has demonstrated linear increase with intrinsic layer length and proton-radiation fluence. But the most important obtained result has been the determination of a particular set of semiconductor P-, I- and N-layer thicknesses, for given values of total device length and incident light intensity, that minimize radiation effects during photodiode operation in space environments up to high particle fluences.