Advanced Characterization of 1 eV GaInAs Inverted Metamorphic Solar Cells
Author:
Galiana Beatriz1ORCID, Navarro Amalia1ORCID, Hinojosa Manuel2, Garcia Ivan2, Martin-Martin Diego3ORCID, Jiménez Juan4ORCID, García-Tabarés Elisa1ORCID
Affiliation:
1. Physics Department, Universidad Carlos III de Madrid (UC3M), Av. Universidad 40, 28911 Leganés, Spain 2. Solar Energy Institute, Universidad Politécnica de Madrid (IES-UPM), Av. Complutense s/n, 28040 Madrid, Spain 3. Departamental II, Universidad Rey Juan Carlos, C. Tulipán, s/n, 28933 Móstoles, Spain 4. GdS Optronlab, Universidad de Valladolid (UVA), Paseo de Belén 11, 47011 Valladolid, Spain
Abstract
In this work, 1 eV Ga0.7In0.3As inverted metamorphic (IMM) solar cells were analyzed to achieve a deeper understanding of the mechanism limiting their improvement. For this purpose, high-resolution X-ray diffraction (HRXRD), transmission electron microscopy (TEM), high-resolution cross-sectional cathodoluminescence (CL), and transient in situ surface reflectance were carried out. Additionally, the photovoltaic responses of the complete devices were measured using the external quantum efficiency (EQE) and numerically simulated through Silvaco TCAD ATLAS. The combination of structural characterization of the semiconductor layers and measurements of the solar cell photovoltaic behavior, together with device modeling, allows us to conclude that the lifetime of the bulk minority carriers is the limiting factor influencing the PV response since the recombination at the interfaces (GaInP window–GaInAs emitter and GaInAs base–GaInP back surface field (BSF)) does not impact the carrier recombination due to the favorable alignment between the conduction and the valance bands. The advanced characterization using cross-sectional cathodoluminescence, together with transient in situ surface reflectance, allowed the rejection of the formation of traps related to the GaInAs growth conditions as being responsible for the decrement in the minority-carrier lifetime. Conversely, the TEM and HRXRD revealed that the presence of misfit dislocations in the GaInAs layer linked to strain relaxation, which were probably formed due to an excessive tensile strain in the virtual substrate or an incorrect combination of alloy compositions in the topmost layers, was the dominant factor influencing the GaInAs layer’s quality. These results allow an understanding of the contributions of each characterization technique in the analysis of multi-junction solar cells.
Funder
project RENOAIX200 project LABCELL30
Subject
Energy (miscellaneous),Energy Engineering and Power Technology,Renewable Energy, Sustainability and the Environment,Electrical and Electronic Engineering,Control and Optimization,Engineering (miscellaneous),Building and Construction
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