CdTe Back Contact Engineering via Nanomaterials, Chemical Etching, Doping, and Surface Passivation

CdTe Back Contact Engineering via Nanomaterials, Chemical Etching, Doping, and Surface Passivation

Bibliographic Details
Main Author: Bastola, Ebin
Language:English
Published: University of Toledo / OhioLINK 2020
Subjects:
Physical Chemistry
Physics
Nanoscience
Nanotechnology
Nanomaterials
Nanocrystals
Photovoltaics
Solar Cells
CdTe
SILAR
Sputtering
Etching
Surface Passivation
Doping
Iron Selenide
Iron Telluride
Chalcopyrite
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=toledo1596813646708798
id ndltd-OhioLink-oai-etd.ohiolink.edu-toledo1596813646708798
record_format oai_dc
collection NDLTD
language English
sources NDLTD
topic Physical Chemistry
Physics
Nanoscience
Nanotechnology
Nanomaterials
Nanocrystals
Photovoltaics
Solar Cells
CdTe
SILAR
Sputtering
Etching
Surface Passivation
Doping
Iron Selenide
Iron Telluride
Chalcopyrite
spellingShingle Physical Chemistry
Physics
Nanoscience
Nanotechnology
Nanomaterials
Nanocrystals
Photovoltaics
Solar Cells
CdTe
SILAR
Sputtering
Etching
Surface Passivation
Doping
Iron Selenide
Iron Telluride
Chalcopyrite
Bastola, Ebin
CdTe Back Contact Engineering via Nanomaterials, Chemical Etching, Doping, and Surface Passivation
author Bastola, Ebin
author_facet Bastola, Ebin
author_sort Bastola, Ebin
title CdTe Back Contact Engineering via Nanomaterials, Chemical Etching, Doping, and Surface Passivation
title_short CdTe Back Contact Engineering via Nanomaterials, Chemical Etching, Doping, and Surface Passivation
title_full CdTe Back Contact Engineering via Nanomaterials, Chemical Etching, Doping, and Surface Passivation
title_fullStr CdTe Back Contact Engineering via Nanomaterials, Chemical Etching, Doping, and Surface Passivation
title_full_unstemmed CdTe Back Contact Engineering via Nanomaterials, Chemical Etching, Doping, and Surface Passivation
title_sort cdte back contact engineering via nanomaterials, chemical etching, doping, and surface passivation
publisher University of Toledo / OhioLINK
publishDate 2020
url http://rave.ohiolink.edu/etdc/view?acc_num=toledo1596813646708798
work_keys_str_mv AT bastolaebin cdtebackcontactengineeringviananomaterialschemicaletchingdopingandsurfacepassivation
_version_ 1719474154611146752
spelling ndltd-OhioLink-oai-etd.ohiolink.edu-toledo15968136467087982021-09-02T05:10:39Z CdTe Back Contact Engineering via Nanomaterials, Chemical Etching, Doping, and Surface Passivation Bastola, Ebin Physical Chemistry Physics Nanoscience Nanotechnology Nanomaterials Nanocrystals Photovoltaics Solar Cells CdTe SILAR Sputtering Etching Surface Passivation Doping Iron Selenide Iron Telluride Chalcopyrite <p>Energy is considered one of the top problems facing humanity, and climate change clearly require3s growth in the fraction of energy provided by renewable sources in order to minimize the use of fossil fuels. Solar energy is an environmentally friendly technology which avoids nearly all generation of greenhouse gases. It is more available than hydro, wind, and other renewable energy sources. As science and technology advance, various types of solar cells are being produced to harvest solar energy. Silicon technology dominates the photovoltaic (PV) industry. Thin film solar electric technologies are evolving to reduce the cost of energy ($/Watt). Cadmium telluriude (CdTe) is one of the leading thin film technologies with a reduced energy cost and the shortest energy payback time.</p><p>CdTe is a direct band gap II-VI material and has been investigated for decades to improve device performance, stability, and conversion efficiency. However, the open-circuit voltage (V<sub>OC</sub>) of CdTe devices is lower than for GaAs solar cells, despite having similar energy band gaps. Simulation and theoretical study show that the voltage deficit can be improved by making an ohmic contact to CdTe, or by reducing the back-contact potential barrier and increasing the doping level of CdTe. In this dissertation, I report on nanomaterials-based back contact interface layers, surface etching, the doping of CdTe using copper (II) chloride (CuCl<sub>2</sub>), and on the opto-electronic properties of CdTe double heterostructure samples.</p><p>Nanocrystals (NCs) of FeSe<sub>2</sub>, FeTe<sub>2</sub>, Ni<sub>x</sub>Fe<sub>1-x</sub>S<sub>2</sub>, and CuFeS<sub>2</sub> were synthesized using hot injection colloidal methods. These materials were then characterized using X-ray diffraction, electron microscopy, Raman and UV-Vis-NIR spectroscopies. The charge transport properties of these nanomaterial-based thin films were tested in CdTe photovoltaics. Nickel iron pyrite (Ni<sub>x</sub>Fe<sub>1-x</sub>S<sub>2</sub>) NCs showed composition-controlled conductivity, and where <i>x</i> = 0.05 (5%), they showed optimal device performance when applied as a hole transport layer in CdTe photovoltaics. Similarly, room temperature processed earth abundant Cu-Zn-S nanocomposite thin films prepared by the SILAR method can serve as a low barrier back-contact interface layer in CdTe PV.</p><p>In this dissertation, I also explored the selective etching of CdTe photovoltaics using iodine compounds. Iodine etching of the CdTe surface produced a Te rich layer, which reduced the back-barrier potential and improved the device performance. The highest device performance was about 14.0% for CdS/CdTe solar cells with a fill factor of 78.2%. Similarly, doping CdTe solar cells using a CuCl<sub>2</sub> solution in deionized water was found to be more effective than evaporated copper. For sputtered CdS/CdTe devices, a V<sub>OC</sub> exceeding 840 mV was obtained. The solution-based Cu doping improved the device performance by enhancing the opto-electronic properties of CdTe (as measured by time-resolved photoluminescence) and by increasing the free carrier concentration as determined by capacitance-voltage measurements. In addition, the atomic layer deposited alumina (Al<sub>2</sub>O<sub>3</sub>) was found to passivate CdTe surfaces.</p> 2020 English text University of Toledo / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=toledo1596813646708798 http://rave.ohiolink.edu/etdc/view?acc_num=toledo1596813646708798 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

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