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Journal of Green EngineeringJournal divested in January 2019, new journal website is: www.jgenng.com

Editor-in-Chief: Michele Albano, ISEP - Instituto Superior de Engenharia do Porto, Portugal

ISSN: 1904-4720 (Print Version),

ISSN: 2245-4586 (Online Version)
Vol: 5   Issue: Combined Issue 3 & 4

Published In:   July 2015

Publication Frequency: Quarterly

Search Available Volume and Issue for Journal of Green EngineeringJournal divested in January 2019, new journal website is: www.jgenng.com

Journal Description        Editorial Foreword        Read Full Articles        Editorial Board        Subscription        Indexed

Modelling of Cu(In,Ga)Se2 Solar Materials/Devices

doi: https://doi.org/10.13052/jge1904-4720.5341
N. Bednar, N. Severino and N. Adamovic

Institute of Sensor and Actuator Systems, Vienna University of Technology, Gusshausstrasse 27–29, 1040 Vienna, Austria

Abstract: [+]    |    Download File [ 1725KB ]    |   Read Article Online

Abstract: This paper will present the numerical modelling of CIGS materials/devices in order to better understand the physical properties of the device, having the goal to support/improve the fabrication technology based on an alternative hybrid sputtering/evaporation deposition. Optimization of the buffer- and absorption layer for high efficiency CIGS solar cells will be presented, since the band gap can be graded over a wide range by changing the Ga concentration in the thin film layer, which greatly affects the efficiency of the solar cell. The dependence of the solar cell properties on the thickness of the buffer layer and the effects of the bulk and interfaces defects on the solar cell parameters have been studied.

The hybrid approach to modelling and simulation of thin film solar cells with a metal front grid on top of the transparent conductive oxide based electrode will be presented. A 3D model with high aspect ratio of device thickness (100s of nm) and its length and width (mm and cm range) was divided into two coupled models with different number of spatial dimensions (a 1D and a 3D model) on different length scales. The first one covers the modelling on the material stack level. The second model is coupled with the first and it takes into account the photovoltaic device’s geometry. This approach enables the separation of the technology-dependent material simulation from the device shape and front grid design simulation. The metallization in the form of parallel fingers was investigated and optimized for the described case study. Finally, the efficiency of solar thin-film modules using optimized cells with different widths will be explored, thus enabling the tuning of the output voltage of the solar module while the power output remains unchanged.

Keywords: CIGS, thin-film, solar cells, modelling, simulation.

Towards a Multi-scale Approach to the Simulation of Silicon Hetero-junction Solar Cells

doi: https://doi.org/10.13052/jge1904-4720.5342
Urs Aeberhard1, Philippe Czaja1, Markus Ermes1, Bart E. Pieters1, Ganna Chistiakova1, Karsten Bittkau1, Alexei Richter1, Kaining Ding1, Simone Giusepponi2 and Massimo Celino2

1IEK-5 Photovoltaik, Forschungszentrum Jülich, D-52425 Jülich, Germany
2ENEA, C.R. Casaccia, Via Anguillarese 301, 00123 Rome, Italy

Abstract: [+]    |    Download File [ 4193KB ]    |   Read Article Online

Abstract: The silicon hetero-junction (SHJ) technology holds the current efficiency record of 25.6% for silicon-based single junction solar cells and shows great potential to become a future industrial standard for high-efficiency crystalline silicon (c-Si) cells. One of the main advantages of this concept over other wafer based silicon technologies are the very high open-circuit voltages that can be achieved thanks to the passivation of contacts by thin films of hydrogenated amorphous silicon (a-Si:H). The a-Si:H/c-Si interface, while central to the technology, is still not fully understood in terms of transport and recombination across this nanoscale region, especially concerning the role of the different localized tail and defect states in the a-Si:H and at the a-Si:H/c-Si interface and of the band offsets and band bending induced by the heterostructure potential and the large doping, respectively. For instance, a consistent microscopic picture of transport and recombination processes with treatment of thermal and tunneling mechanisms on equal footing is lacking. On the other hand, there are new SHJ device architectures like thin wafers with light trapping structures [1] or interdigitated back contact (IBC) cells [2], which define additional requirements for the modelling approach concerning the integration of 3D optical and electrical simulations. This paper provides an overview over our current efforts in the creation of a multi-scale and multi-physics framework to deal with the challenges encountered in the simulation of SHJ solar cells.

Keywords: Multiscale simulation, silicon heterojunction, solar cell.

SPICE Modelling of Photoluminescence and Electroluminescence Based Current-Voltage Curves of Solar Cells for Concentration Applications

doi: https://doi.org/10.13052/jge1904-4720.5343
D. Alonso-Álvarez and N. Ekins-Daukes

Imperial College London, London, United Kingdom

Abstract: [+]    |    Download File [ 2957KB ]    |   Read Article Online

Abstract: Quantitative photoluminescence (PL) or electroluminescence (EL) experiments can be used to probe fast and in a non-destructive way the currentvoltage (IV) characteristics of individual subcells in a multi-junction device, information that is, otherwise, not available. PL-based IV has the advantage that it is contactless and can be performed even in partly finished devices, allowing for an early diagnosis of the expected performance of the solar cells in the production environment. In this work we simulate the PL- and ELbased IV curves of single junction solar cells to assess their validity compared with the true IV curve and identify injection regimes where artefacts might appear due to the limited in-plane carrier transport in the solar cell layers. We model the whole photovoltaic device as a network of sub-circuits, each of them describing the solar cell behaviour using the two diode model. The subcircuits are connected to the neighbouring ones with a resistor, representing the in-plane transport in the cell. The resulting circuit, involving several thousand sub-circuits, is solved using SPICE.

Keywords: Semiconductors, multi-junction solar cells, photoluminescence, SPICE.

An Outlook on Silicon Nanocrystals for Optoelectronics

doi: https://doi.org/10.13052/jge1904-4720.5344
I. Capan1, A. Carvalho2 and J. Coutinho3

1Rudjer Boskovic Institute, P.O. Box 180, 10000 Zagreb, Croatia
2Graphene Research Centre and Department of Physics, National University of Singapore, 117542, Singapore
3Department of Physics and I3N, University of Aveiro, Campus Universitario de Santiago, 3810-193 Aveiro, Portugal

Abstract: [+]    |    Download File [ 2136KB ]    |   Read Article Online

Abstract: Silicon nanocrystals have emerged as promising material components which extend the realm of the application of its bulk counterpart beyond traditional boundaries. Over the last two decades of research, their potential for application on areas that range from optoelectronics to information storage has been progressively unraveled. Nevertheless, as technology steps forward, new challenges are arising. Here we consider what has been achieved and what are the current limitations on the fields of growth, characterization and modeling of silicon nanocrystals.

Keywords: Characterization, modelling, nanocrystals, silicon.

Amplification of the Zeroth Order Mode in Ultra-thin Layers

doi: https://doi.org/10.13052/jge1904-4720.5345
José M. Llorens, Jerónimo Buencuerpo, José M. Ripalda and Pablo A. Postigo

IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), Isaac Newton 8, PTM, E-28760 Tres Cantos, Madrid, Spain

Abstract: [+]    |    Download File [ 1501KB ]    |   Read Article Online

Abstract: The ultra-thin limit regime is characterized by a structure which at least in one dimension is significantly smaller than the incoming light wavelength. The absorption in this regime is characterized either by very weak absorption or by a broad peak attributed to the zeroth order Fabry-Perot mode. We show that this mode provides a 14.5% ultimate efficiency in a 25 nm GaAs slab on a gold substrate. GaAs in air achieves only a 5% for a 10 nm slab. Such an amplification of the resonance absorption is attributed to the high losses of the substrate. For very high losses, the zeroth order mode transits from an over-damped regime to an under-damped one.

Keywords: Solar cells, absorption, quasinormal modes, optics, optical coating.

The Advantages of Spark Discharge Generation for Manufacturing of Nanoparticles with Tailored Properties

doi: https://doi.org/10.13052/jge1904-4720.5346
Maria E. Messing

Solid State Physics, NanoLund, Lund University, Box 118, 221 00 Lund, Sweden

Abstract: [+]    |    Download File [ 920KB ]    |   Read Article Online

Abstract: The number of nanoparticle-based products on the market is expected to increase considerably during the coming decades. For this to happen a solid supply of high-quality nanoparticles is needed. For metal nanoparticles no large-scale manufacturing method exists today but production using spark discharge generation is believed to be one of the most suitable candidates. Spark discharge generation offers several advantages over other methods and the first steps towards scaling up have already been taken. In this paper the spark discharge generator concept is presented and its advantages are discussed. Examples of nanoparticle materials and applications for the as-generated particles are reviewed.

Keywords: Nanoparticles, spark discharge generation, aerosols.

Semiempirical Modelling of a Nanostructured Photoanode Profile for Highly EfficientWater Splitting: Three Sublayers Concept

doi: https://doi.org/10.13052/jge1904-4720.5347
Mimoza M. Ristova1,2, Kin Man Yu1,3 and Wladyslaw Walukiewicz1

1Solar Energy Materials Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, B2, Berkeley CA 94720, USA
2Institute of Physics, Faculty of Natural Sciences and Mathematics, Arhimedova 10, University in Skopje, 1000 Skopje, Republic of Macedonia
3Department of Physics and Materials Science, City University of Hong Kong, Hong Kong

Abstract: [+]    |    Download File [ 3382KB ]    |   Read Article Online

Abstract: We present semiempirical modeling of conceptually new CdxZn1-xO/NiyCd1-yO based nanostructured photoanode, composed of three sublayers: Absorber (ABS), Grading (GRAD) and Barrier (BAR), for highly efficient photocatalytic water dissociation. Our modeling resulted into ABS made of Cd0.55Zn0.45O due to its favorable positions of the valence and conduction band on the water splitting potentials and a band gap ~2.0 eV. The GRAD was composed of CdxZn1-xO with a gradual decrease of x across the profile, resulting in a gradual band gap change from 2.0 to 3.1 eV. At the same time, GRAD provides the profile with an implanted electrical field that improves the hole survival rate. The BAR was engineered in a manner that provides 1 eV barrier in the conduction band. It was made of 50 nm thick Ni0.4Cd0.6O film with Eg ~3.0 eV. The BAR's valence band is well aligned to the one of the GRAD, providing a barrier-free hole transport. In this paper, we prove that the proposed modeling of the three individual layers clearly represents a new paradigm for an improved efficiency for photoelectrochemical water splitting.

Keywords: CdxZn1-xO/Niy Cd1-yO, photoanodes, water splitting, voltammetry, IPCE energy efficiency.

High Efficiency Dilute Nitride Solar Cells: Simulations Meet Experiments

doi: https://doi.org/10.13052/jge1904-4720.5348
A. Tukiainen, A. Aho, V. Polojarvi, R. Ahorinta and M. Guina

Optoelectronics Research Centre, Tampere University of Technology, Korkeakoulunkatu 3, FI-33720 Tampere, Finland

Abstract: [+]    |    Download File [ 4003KB ]    |   Read Article Online

Abstract: Parameter extraction procedure and simulation of dilute nitride solar cells are reported. Using PC1D simulation and fitting to experimental current-voltage and external quantum efficiency data, we retrieve the phenomenological material parameters for GaInNAs solar cells. Based on these, we have constructed a model that can explain the changes in short circuit current and open circuit voltage of n-i-p solar cells subjected to rapid thermal annealing. The model reveals that non-annealed MBE-grown GaInNAs material has an n-type doping that evolves to p-type upon rapid thermal annealing. The change of doping type and the shift of the physical location of the pn-junction were confirmed by Kelvin-probe force microscopy. The PC1D modelling was found to work well also for GaInNAs p-i-n solar cells with opposite polarity. It was also found that the GaInNAs lower doping levels in p-i-n solar cells grown at lowered As/III flux ratios were associated with increased carrier lifetimes.

Keywords: GaInNAs-based semiconductors

Multiscale Approaches for the Simulation of Optoelectronic Devices

doi: https://doi.org/10.13052/jge1904-4720.5349
Matthias Auf der Maur

University of Rome Tor Vergata, Rome, Italy

Abstract: [+]    |    Download File [ 1889KB ]    |   Read Article Online

Abstract: Multiscale approaches for electronic device simulation have become a subject of high interest during the last decade. In this article we will give an overview on the current activities in the field.We will provide some practical examples from optoelectronics where multiscale simulations can be useful. Basic coupling schemes are discussed, and approaches for the combination of continuous models and models with atomistic resolution are described.

Keywords: multiscale simulation, optoelectronic devices.

Trends, Challenges and Opportunities in Advanced Solar Cells Technologies and PV Market

doi: https://doi.org/10.13052/jge1904-4720.53410
Laurentiu Fara1,2 Alexandru Diaconu1 and Florin Dragan1

1Polytechnic University of Bucharest (PUB), Splaiul Independentei 313, Sector 6, RO 060032 Bucharest, Romania
2Academy of Romanian Scientists

Abstract: [+]    |    Download File [ 1473KB ]    |   Read Article Online

Abstract: Selected results in modelling and numerical simulation of advanced solar cells obtained by the Solar Energy Group from the Faculty of Applied Sciences of PUB (SEG-FSA) are highlighted. The opportunities for PV development together with the world PV market performances, relevant European PV market features and the forecasts until 2018 are discussed.

Keywords: Trends, challenges, opportunities, advanced solar cells, modelling and simulation, PV market, forecasting.

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