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Digitale Dissertation

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Chemical bath deposition of zinc compounds for cadmiumfree solar cells
Chemische Badabscheidung von Zinkverbindungen für cadmiumfreie Solarzellen

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Abstract

The present work studied the deposition and characteristics of thin films of different zinc compounds, which are used for photovoltaic applications. The process has been in situ examinated by photon correlation spectroscopy and quartz crystal microbalance experiments. In addition ex situ methods as different microscopy techniques, various spectroscopy methods and ERDA-investigations were performed to study the characteristics of the films. The films consist of nanocrystalline particles in an amorphous matrix and are formed mainly by the adsorption of colloids at the substrate surface. The influence of the solution parameters on composition and morphology of the deposited films was studied. The formation of the colloids is supported by hydrazine, which has a complexing effect for the zinc ions. For this reason presence of hydrazine is supporting the film formation. A strong effect of the pH of the solution is revealed: At pH-values above 11.6 ZnS growth is dominant, while at lower pH mainly ZnO and Zn(OH)2 are the dominant products. Hence, the pH of the solution can be used to adjust the film stoichiometry. Thermodynamic reasons and kinetic factors as the gradually thiourea decomposition has an influence on the process. The influence of the reaction conditions is not strictly predicable. Kinetic and thermodynamic influences can have a contrasting impact. Therefore the experimental results of this study are of great value. Buffer layers developed within the work of this studies are able to replace the commonly used CdS layer within thin film solar cells. Cadmiumfree solar cells with effenciencies of about 10% were made. Regarding the higher band gap of the zinc compounds there is a potential to further improvements of the CIS solar cells parameters. For this reason there is a big interest to bring in further efforts and investigations in the CIS system with respect to the photovoltaic application.

Table of Contents

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TITELSEITE UND INHALT
1 EINFÜHRUNG 1
2 GRUNDLAGEN 4
2.1 Wachstum dünner Schichten 4
2.2 Übersättigung und Ostwald-Miers-Bereich 7
2.3 Chemische Badabscheidung 10
2.4 Thermodynamische Grundlagen 14
2.5 Einfluß kinetischer Faktoren 17
2.6 Heterokontaktsolarzellen auf CuInS2-Basis 19
3 EXPERIMENTE 22
3.1 Herstellung der Lösungen und Schichten 22
3.2 Analytische Untersuchungen 24
3.2.1 Photonenkorrelationsspektroskopie 24
3.2.2 Schwingquarzmessungen 25
3.2.3 Rasterelektronenmikroskopie 25
3.2.4 Atomkraftmikroskopie 26
3.2.5 Elastic Recoil Detection Analysis 26
3.2.6 Photoelektronenspektroskopie 27
3.2.7 Transmissionselektronenmikroskopie 28
3.2.8 Elektronenbeugung 29
3.3 Herstellung und Charakterisierung von Solarzellen 30
4 ERGEBNISSE 32
4.1 Kolloidbildung in der Lösung 32
4.2 Beschreibung der Schichten 36
4.3 Morphologie und Nanostrukturierung 40
4.4 Einfluß der Konzentrationsverhältnisse in der Lösung 49
4.4.1 Einfluß des Hydrazins 49
4.4.2 Thioharnstoffkonzentration 50
4.4.3 Einfluß des Ammoniaks 53
4.4 Charakterisierung und Effiziens der Solarzellen 55
5 DISKUSSION 59
5.1 Kolloidbildung und Schichtwachstum 59
5.2 Steuerung der Stöchiometrie 62
5.3 Reaktionsmechanismus 66
5.4 Vergleich thermodynamischer und kinetischer Effekte 69
5.5 Einsatzmöglichkeiten der Schichten in Solarzellen 71
6 ZUSAMMENFASSUNG 73
7 LITERATUR UND ABKÜRZUNGSVERZEICHNIS 75

More Information:

Online available: http://www.diss.fu-berlin.de/2002/14/indexe.html
Language of PhDThesis: german
Keywords: thin film growth, buffer layers, zinc compounds, solar cells
DNB-Sachgruppe: 30 Chemie
Date of disputation: 13-Dec-2001
PhDThesis from: Fachbereich Biologie, Chemie, Pharmazie, Freie Universität Berlin
First Referee: Prof. Dr. Helmut Tributsch
Second Referee: Prof. Dr. Jürgen Dohrmann
Contact (Author): sneve@mpi-halle.de
Contact (Advisor): tributsch@hmi.de
Date created:31-Jan-2002
Date available:01-Feb-2002

 

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